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we present results from an atmospheric circulation study of nine hot jupiters that compose a large transmission spectral survey using the hubble and spitzer space telescopes. these observations exhibit a range of spectral behavior over optical and infrared wavelengths, suggesting diverse cloud and haze properties in their atmospheres. by utilizing the specific system parameters for each planet, we naturally probe a wide phase space in planet radius, gravity, orbital period, and equilibrium temperature. first, we show that our model “grid” recovers trends shown in traditional parametric studies of hot jupiters, particularly equatorial superrotation and increased day-night temperature contrast with increasing equilibrium temperature. we show how spatial temperature variations, particularly between the dayside and nightside and west and east terminators, can vary by hundreds of kelvin, which could imply large variations in na, k, co and {{{ch}}}4 abundances in those regions. these chemical variations can be large enough to be observed in transmission with high-resolution spectrographs, such as espresso on vlt, metis on the e-elt, or miri and nirspec aboard jwst. we also compare theoretical emission spectra generated from our models to available spitzer eclipse depths for each planet and find that the outputs from our solar-metallicity, cloud-free models generally provide a good match to many of the data sets, even without additional model tuning. although these models are cloud-free, we can use their results to understand the chemistry and dynamics that drive cloud formation in their atmospheres. | the atmospheric circulation of a nine-hot-jupiter sample: probing circulation and chemistry over a wide phase space |
accurate estimation of planetary boundary layer height (pblh) is key to air quality prediction, weather forecast, and assessment of regional climate change. the pblh retrieval from the cloud-aerosol lidar with orthogonal polarization (caliop) is expected to complement ground-based measurements due to the broad spatial coverage of satellites. in this study, caliop pblhs are derived from combination of haar wavelet and maximum variance techniques, and are further validated against pblhs estimated from ground-based lidar at beijing and jinhua. correlation coefficients between pblhs from ground- and satellite-based lidars are 0.59 at beijing and 0.65 at jinhua. also, the pblh climatology from caliop and radiosonde are compiled over china during the period from 2011 to 2014. maximum caliop-derived pblh can be seen in summer as compared to lower values in other seasons. three matchup scenarios are proposed according to the position of each radiosonde site relative to its closest calipso ground tracks. for each scenario, intercomparisons were performed between caliop- and radiosonde-derived pblhs, and scenario 2 is found to be better than other scenarios using difference as the criteria. in early summer afternoon over 70 % of the total radiosonde sites have pblh values ranging from 1.6 to 2.0 km. overall, caliop-derived pblhs are well consistent with radiosonde-derived pblhs. to our knowledge, this study is the first intercomparison of pblh on a large scale using the radiosonde network of china, shedding important light on the data quality of initial caliop-derived pblh results. | planetary boundary layer height from caliop compared to radiosonde over china |
astronomers commonly quote the properties of celestial objects in units of parameters for the sun, jupiter, or the earth. the resolution presented here was proposed by the iau inter-division working group on nominal units for stellar and planetary astronomy and passed by the xxixth iau general assembly in honolulu. iau 2015 resolution b3 adopts a set of nominal solar, terrestrial, and jovian conversion constants for stellar and (exo)planetary astronomy which are defined to be exact si values. while the nominal constants are based on current best estimates (cbes; which have uncertainties, are not secularly constant, and are updated regularly using new observations), they should be interpreted as standard values and not as cbes. iau 2015 resolution b3 adopts five solar conversion constants (nominal solar radius, nominal total solar irradiance, nominal solar luminosity, nominal solar effective temperature, and nominal solar mass parameter) and six planetary conversion constants (nominal terrestrial equatorial radius, nominal terrestrial polar radius, nominal jovian equatorial radius, nominal jovian polar radius, nominal terrestrial mass parameter, and nominal jovian mass parameter). | iau 2015 resolution b3 on recommended nominal conversion constants for selected solar and planetary properties |
interplanetary dust particles hit the surfaces of airless bodies in the solar system, generating charged and neutral gas clouds, as well as secondary ejecta dust particles. gravitationally bound ejecta clouds that form dust exospheres were recognized by in situ dust instruments around the icy moons of jupiter and saturn, but have hitherto not been observed near bodies with refractory regolith surfaces. high-altitude apollo 15 and 17 observations of a `horizon glow' indicated a putative population of high-density small dust particles near the lunar terminators, although later orbital observations yielded upper limits on the abundance of such particles that were a factor of about 104 lower than that necessary to produce the apollo results. here we report observations of a permanent, asymmetric dust cloud around the moon, caused by impacts of high-speed cometary dust particles on eccentric orbits, as opposed to particles of asteroidal origin following near-circular paths striking the moon at lower speeds. the density of the lunar ejecta cloud increases during the annual meteor showers, especially the geminids, because the lunar surface is exposed to the same stream of interplanetary dust particles. we expect all airless planetary objects to be immersed in similar tenuous clouds of dust. | a permanent, asymmetric dust cloud around the moon |
global climate change has attracted worldwide attention. the ocean is the largest active carbon pool on the planet and plays an important role in global climate change. however, marine plastic pollution is getting increasingly serious due to the large consumption and mismanagement of global plastics. the impact of marine plastics on ecosystem responsible for the gas exchange and circulation of marine co2 may cause more greenhouse gas emissions. consequently, in this paper, threats of marine microplastics to ocean carbon sequestration are discussed. marine microplastics can 1) affect phytoplankton photosynthesis and growth; 2) have toxic effects on zooplankton and affect their development and reproduction; 3) affect marine biological pump; and 4) affect ocean carbon stock. phytoplankton and zooplankton are the most important producer and consumer of the ocean. as such, clearly, further research should be needed to explore the potential scale and scope of this impact, and its underlying mechanisms. | can microplastics pose a threat to ocean carbon sequestration? |
geochemical data for h2o and other volatiles, as well as major and trace elements, are reported for 377 samples of lunar volcanic glass from three chemical groups (a15 green, a15 yellow, a17 orange 74 220). these data demonstrate that degassing is a pervasive process that has affected all extrusive lunar rocks. the data are combined with published data to estimate the total composition of the bulk silicate moon (bsm). the estimated bsm composition for highly volatile elements, constrained by h2o/ce ratios and s contents in melt inclusions from orange glass sample 74 220, are only moderately depleted compared with the bulk silicate earth (avg. 0.25x bse) and essentially overlap the composition of the terrestrial depleted morb source. in a single giant impact origin for the moon, the moon-forming material experiences three stages of evolution characterized by very different timescales. impact mass ejection and proto-lunar disk evolution both permit system loss of h2o and other volatiles on timescales ranging from days to centuries; the early moon is likely to have accreted from a thin magma disk of limited volume embedded in, but largely displaced from, the extended distribution of vapor around the earth. only the protracted evolution of the lunar magma ocean (lmo) presents a time window sufficiently long (10-200 ma) for the moon to gain water during the tail end of accretion. this "hot start" to lunar formation is however not the only model that matches the lunar volatile abundances; a "cold start" in which the proto-lunar disk is largely composed of solid material could result in efficient delivery of terrestrial water to the moon, while a "warm start" producing a disk of 25% volatile-retentive solids and 75% volatile-depleted magma/vapor is also consistent with the data. at the same time, there exists little evidence that the moon formed in a singular event, as all detailed planetary accretion models predict several giant impacts in the terrestrial planet region in which the earth forms. it is thus conceivable that the moon, like the earth, experienced a history of heterogeneous accretion. | water in the moon's interior: truth and consequences |
wetlands are a critical component of the landscape for climate mitigation, adaptation, biodiversity, and human health and prosperity. keeping an eye on wetland vegetation is crucial due to it playing a major role in the planet's carbon cycle and ecosystem management. by measuring the chlorophyll fluorescence (chf) emitted by plants, we can get a precise understanding of the current state and photosynthetic activity. in this study, we applied the extreme gradient boost (xgboost) algorithm to map chf in the biebrza valley, which has a unique ecosystem in europe for peatlands, as well as highly diversified flora and fauna. our results revealed the advantages of using a set of classifiers derived from eo sentinel-2 (s-2) satellite image mosaics to accurately map the spatio-temporal distribution of chf in a terrestrial landscape. the validation proved that the xgboost algorithm is quite accurate in estimating chf with a good determination of 0.71 and least bias of 0.012. the precision of chlorophyll fluorescence measurements is reliant upon determining the optimal s-2 satellite overpass time, which is influenced by the developmental stage of the plants at various points during the growing season. finally, the model performance results indicated that biophysical factors are characterized by greenness- and leaf-pigment-related spectral indices. however, utilizing vegetation indices based on extended periods of remote sensing data that better capture land phenology features can improve the accuracy of mapping chlorophyll fluorescence. | a machine learning approach for mapping chlorophyll fluorescence at inland wetlands |
regional haze episodes have occurred frequently in eastern china over the past decades. as a critical indicator to evaluate air quality, the mass concentration of ambient fine particulate matters smaller than 2.5 μm in aerodynamic diameter (pm2.5) is involved in many studies. to overcome the limitations of ground measurements on pm2.5 concentration, which is featured in disperse representation and coarse coverage, many statistical models were developed to depict the relationship between ground-level pm2.5 and satellite-derived aerosol optical depth (aod). however, the current satellite-derived aod products and statistical models on pm2.5–aod are insufficient to investigate pm2.5 characteristics at the urban scale, in that spatial resolution is crucial to identify the relationship between pm2.5 and anthropogenic activities. this paper presents a geographically and temporally weighted regression (gtwr) model to generate ground-level pm2.5 concentrations from satellite-derived 500 m aod. the gtwr model incorporates the sara (simplified high resolution modis aerosol retrieval algorithm) aod product with meteorological variables, including planetary boundary layer height (pblh), relative humidity (rh), wind speed (ws), and temperature (temp) extracted from wrf (weather research and forecasting) assimilation to depict the spatio-temporal dynamics in the pm2.5–aod relationship. the estimated ground-level pm2.5 concentration has 500 m resolution at the modis satellite's overpass moments twice a day, which can be used for air quality monitoring and haze tracking at the urban and regional scale. to test the performance of the gtwr model, a case study was carried out in a region covering the adjacent parts of jiangsu, shandong, henan, and anhui provinces in central china. a cross validation was done to evaluate the performance of the gtwr model. compared with ols, gwr, and twr models, the gtwr model obtained the highest value of coefficient of determination (r2) and the lowest values of mean absolute difference (mad), root mean square error (rmse), and mean absolute percentage error (mape). | a geographically and temporally weighted regression model for ground-level pm2.5 estimation from satellite-derived 500 m resolution aod |
we present an advance toward accurately predicting the arrivals of coronal mass ejections (cmes) at the terrestrial planets, including earth. for the first time, we are able to assess a cme prediction model using data over two thirds of a solar cycle of observations with the heliophysics system observatory. we validate modeling results of 1337 cmes observed with the solar terrestrial relations observatory (stereo) heliospheric imagers (hi) (science data) from 8 years of observations by five in situ observing spacecraft. we use the self-similar expansion model for cme fronts assuming 60° longitudinal width, constant speed, and constant propagation direction. with these assumptions we find that 23%-35% of all cmes that were predicted to hit a certain spacecraft lead to clear in situ signatures, so that for one correct prediction, two to three false alarms would have been issued. in addition, we find that the prediction accuracy does not degrade with the hi longitudinal separation from earth. predicted arrival times are on average within 2.6 ± 16.6 h difference of the in situ arrival time, similar to analytical and numerical modeling, and a true skill statistic of 0.21. we also discuss various factors that may improve the accuracy of space weather forecasting using wide-angle heliospheric imager observations. these results form a first-order approximated baseline of the prediction accuracy that is possible with hi and other methods used for data by an operational space weather mission at the sun-earth l5 point. | modeling observations of solar coronal mass ejections with heliospheric imagers verified with the heliophysics system observatory |
a large fraction of giant planets have gaseous envelopes that are limited to about 10% of their total mass budget. such planets are present in the solar system (uranus, neptune) and are frequently observed in short periods around other stars (the so-called super-earths). in contrast to these observations, theoretical calculations based on the evolution of hydrostatic envelopes argue that such low-mass envelopes cannot be maintained around cores exceeding five earth masses. instead, under nominal disk conditions, these planets would acquire massive envelopes through runaway gas accretion within the lifetime of the protoplanetary disk. in this work we show that planetary envelopes are not in hydrostatic balance, which slows down envelope growth. a series of 3d global, radiative hydrodynamical simulations reveal a steady-state gas flow, which enters through the poles and exits in the disk midplane. gas is pushed through the outer envelope in about ten orbital timescales. in regions of the disk that are not significantly dust-depleted, envelope accretion onto cores of about five earth masses can get stalled as the gas flow enters the deep interior. accreted solids sublimate deep in the convective interior, but small opacity-providing grains are trapped in the flow and do not settle, which further prevents rapid envelope accretion. the transition to runaway gas accretion can however be reached when cores grow larger than typical super-earths, beyond 15 earth masses, and preferably when disk opacities are below κ = 1 cm2/g. these findings offer an explanation for the typical low-mass envelopes around the cores of super-earths. | reduced gas accretion on super-earths and ice giants |
after 25 years of laboratory research on protoplanetary dust agglomeration, a consistent picture of the various processes that involve colliding dust aggregates has emerged. besides sticking, bouncing and fragmentation, other effects, like, e.g., erosion or mass transfer, have now been extensively studied. coagulation simulations consistently show that μm-sized dust grains can grow to mm- to cm-sized aggregates before they encounter the bouncing barrier, whereas sub-μm-sized water-ice particles can directly grow to planetesimal sizes. for siliceous materials, other processes have to be responsible for turning the dust aggregates into planetesimals. in this article, these processes are discussed, the physical properties of the emerging dusty or icy planetesimals are presented and compared to empirical evidence from within and without the solar system. in conclusion, the formation of planetesimals by a gravitational collapse of dust "pebbles" seems the most likely. | dust evolution in protoplanetary discs and the formation of planetesimals. what have we learned from laboratory experiments? |
we present hubble space telescope optical and near-ir transmission spectra of the transiting hot-jupiter wasp-31b. the spectrum covers 0.3-1.7 μm at a resolution r ∼ 70, which we combine with spitzer photometry to cover the full-optical to ir. the spectrum is dominated by a cloud deck with a flat transmission spectrum which is apparent at wavelengths > 0.52 μm. the cloud deck is present at high altitudes and low pressures, as it covers the majority of the expected optical na line and near-ir h2o features. while na i absorption is not clearly identified, the resulting spectrum does show a very strong potassium feature detected at the 4.2σ confidence level. broadened alkali wings are not detected, indicating pressures below ∼10 mbar. the lack of na and strong k is the first indication of a sub-solar na/k abundance ratio in a planetary atmosphere (ln[na/k] = -3.3 ± 2.8), which could potentially be explained by na condensation on the planet's night side, or primordial abundance variations. a strong rayleigh scattering signature is detected at short wavelengths, with a 4σ significant slope. two distinct aerosol size populations can explain the spectra, with a smaller sub-micron size grain population reaching high altitudes producing a blue rayleigh scattering signature on top of a larger, lower lying population responsible for the flat cloud deck at longer wavelengths. we estimate that the atmospheric circulation is sufficiently strong to mix micron size particles upwards to the required 1-10 mbar pressures, necessary to explain the cloud deck. these results further confirm the importance of clouds in hot jupiters, which can potentially dominate the overall spectra and may alter the abundances of key gaseous species. | hst hot-jupiter transmission spectral survey: detection of potassium in wasp-31b along with a cloud deck and rayleigh scattering |
context. transitional disks with large dust cavities are important laboratories in which to study planet formation and disk evolution. cold gas may still be present inside these cavities, but quantying this gas is challenging. the gas content is important for constraining the origin of the dust cavity.aims: we use atacama large millimeter/submillimeter array (alma) observations of 12co 6-5 and 690 ghz (band 9) continuum of five well-studied transitional disks. in addition, we analyze previously published band 7 observations of a disk in the 12co 3-2 line and 345 ghz continuum. the observations are used to set constraints on the gas and dust surface density profiles, in particular, the drop δgas of the gas density inside the dust cavity.methods: the physical-chemical modeling code dali was used to simultaneously analyze the gas and dust images. we modeled sr21, hd 135344b, lkca15, sr24s, and rx j1615-3255 (band 9) and j1604-2130 (band 7). the spectral energy distribution and continuum visibility curve constrain the dust surface density. then we used the same model to calculate the 12co emission, which we compared with the observations through spectra and intensity cuts. the amount of gas inside the cavity was quantified by varying the δgas parameter.results: model fits to the dust and gas indicate that gas is still present inside the dust cavity for all disks, but at a reduced level. the gas surface density drops inside the cavity by at least a factor 10, while the dust density drops by at least a factor 1000. disk masses are comparable with previous estimates from the literature, cavity radii are found to be smaller than in the data obtained with the 345 ghz submillimeter array.conclusions: the derived gas surface density profiles suggest that the cavity was cleared by one or more companions in all cases, which trapped the millimeter-sized dust at the edge of the cavity. appendix is available in electronic form at http://www.aanda.org | gas density drops inside dust cavities of transitional disks around young stars observed with alma |
direct imaging of gas giant exoplanets provides information on their atmospheres and the architectures of planetary systems. however, few planets have been detected in blind surveys with direct imaging. using astrometry from the gaia and hipparcos spacecraft, we identified dynamical evidence for a gas giant planet around the nearby star hip 99770. we confirmed the detection of this planet with direct imaging using the subaru coronagraphic extreme adaptive optics instrument. the planet, hip 99770 b, orbits 17 astronomical units from its host star, receiving an amount of light similar to that reaching jupiter. its dynamical mass is 13.9 to 16.1 jupiter masses. the planet-to-star mass ratio [(7 to 8) × 10−3] is similar to that of other directly imaged planets. the planet’s atmospheric spectrum indicates an older, less cloudy analog of the previously imaged exoplanets around hr 8799. | direct imaging and astrometric detection of a gas giant planet orbiting an accelerating star |
we use keck/nirspec to survey a sample of of young (<1 gyr), short-period mini-neptunes orbiting nearby k dwarfs to measure their mass loss via the metastable helium line. we detect helium absorption from all four of the targets in our initial sample. the first detection, around toi 560b, was announced in a previous paper. we now announce three additional detections around toi 1430.01, 2076b, and 1683.01. all four planets show an average in-transit excess absorption of 0.7%-1.0%. however, the outflows differ in their kinematic properties. object toi 1430b exhibits preingress absorption, while toi 2076b's outflow is exceptionally optically thick and shows significant postegress absorption. for all four planets, the width of the measured helium absorption signal is consistent with expectations for a photoevaporative outflow (10-30 km s-1, 5000-10,000 k). unless broadening mechanisms other than thermal velocity and the bulk outflow velocity are significant, our observations disfavor core-powered mass-loss models, which predict much slower (1-3 km s-1) outflows. we utilize both an isothermal parker wind model and an order-of-magnitude method to estimate the mass-loss timescale and obtain ~a few hundred megayears for each planet. we conclude that many, if not all, of these planets will lose their hydrogen-rich envelopes and become super-earths. our results demonstrate that most mini-neptunes orbiting sun-like stars have primordial atmospheres, and that photoevaporation is an efficient mechanism for stripping these atmospheres and transforming these planets into super-earths. | detection of atmospheric escape from four young mini-neptunes |
we identify and study a number of new, rapidly growing instabilities of dust grains in protoplanetary discs, which may be important for planetesimal formation. the study is based on the recognition that dust-gas mixtures are generically unstable to a resonant drag instability (rdi), whenever the gas, absent dust, supports undamped linear modes. we show that the `streaming instability' is an rdi associated with epicyclic oscillations; this provides simple interpretations for its mechanisms and accurate analytic expressions for its growth rates and fastest growing wavelengths. we extend this analysis to more general dust streaming motions and other waves, including buoyancy and magnetohydrodynamic oscillations, finding various new instabilities. most importantly, we identify the disc `settling instability,' which occurs as dust settles vertically into the mid-plane of a rotating disc. for small grains, this instability grows many orders of magnitude faster than the standard streaming instability, with a growth rate that is independent of grain size. growth time scales for realistic dust-to-gas ratios are comparable to the disc orbital period, and the characteristic wavelengths are more than an order of magnitude larger than the streaming instability (allowing the instability to concentrate larger masses). this suggests that in the process of settling, dust will band into rings then filaments or clumps, potentially seeding dust traps, high-metallicity regions that in turn seed the streaming instability, or even overdensities that coagulate or directly collapse to planetesimals. | resonant drag instabilities in protoplanetary discs: the streaming instability and new, faster growing instabilities |
cometary comae are generally depleted in nitrogen. the main carriers for volatile nitrogen in comets are nh3 and hcn. it is known that ammonia readily combines with many acids, such as hcn, hnco and hcooh, encountered in the interstellar medium as well as in cometary ice to form ammonium salts (nh4+x-) at low temperatures. ammonium salts, which can have a substantial role in prebiotic chemistry, are hard to detect in space as they are unstable in the gas phase and their infrared signature is often hidden by thermal radiation or by, for example, oh in minerals. here we report the presence of all possible sublimation products of five different ammonium salts in the comet 67p/churyumov-gerasimenko measured by the rosina instrument onboard rosetta. the relatively high sublimation temperatures of the salts leads to an apparent lack of volatile nitrogen in the coma. this then also explains the observed trend of higher nh3/h2o ratios with decreasing perihelion distances in comets. | evidence of ammonium salts in comet 67p as explanation for the nitrogen depletion in cometary comae |
context. optical interferometry is at a key development stage. the very large telescope interferometer (vlti) has established a stable, robust infrastructure for long-baseline interferometry that is usable by general astronomical observers. the present second-generation instruments offer a wide wavelength coverage and improved performance. their sensitivity and measurement accuracy lead to data and images of high reliability.aims: we have developed the multi aperture mid-infrared spectroscopic experiment (matisse) to access, for the first time, high resolution imaging in a wide spectral domain. many front-line topics are explored with this new equipment, including: stellar activity and mass loss; planet formation and evolution in the gas and dust disks around young stars; and environment interaction and accretion processes around super massive black holes in active galactic nuclei.methods: the instrument is a spectro-interferometric imager in the transmission windows called l, m, and n, from 2.8 to 13.0 microns, combining four optical beams from the vlti's unit or auxiliary telescopes. its concept, related observing procedure, data reduction, and calibration approach, is the product of 30 years of instrumental research and has benefitted from the expertise developed in the frame of the vlti's first generation instruments. the instrument utilises a multi-axial beam combination that delivers spectrally dispersed fringes. the signal provides the following quantities at several spectral resolutions: photometric flux, coherent fluxes, visibilities, closure phases, wavelength differential visibilities and phases, and aperture-synthesis imaging.results: this article provides an overview of the physical principle of the instrument and its functionalities. the motivation of the choice of the instrumental concept and the characteristics of the delivered signal are detailed with a description of the observing modes and of their performance limit. matisse offers four spectral resolutions in l&m bands, namely 30, 500, 1000 and 3400, and 30 and 220 in the n band, and it provides an angular resolution down to 3 mas for the shortest wavelengths. the matisse stand-alone sensitivity limits are 60 mjy in l and 300 mjy in n. the paper gives details of the sensitivity limits for the different measurables and their related precision criteria, considering telescope configurations and spectral resolutions. we also discuss the gain provided with the gra4mat fringe tracker. an ensemble of data and reconstructed images illustrate the first acquired key observations.conclusions: the instrument has been in operation at cerro paranal, eso, chile, since 2018, and has been open for science use by the international community since april 2019. the first scientific results are being published now. | matisse, the vlti mid-infrared imaging spectro-interferometer |
we present a search for outer solar system objects in the 6 yr of data from the dark energy survey (des). the des covered a contiguous 5000 deg2 of the southern sky with ≈80,000 3 deg2 exposures in the grizy filters between 2013 and 2019. this search yielded 812 trans-neptunian objects (tnos), one centaur and one oort cloud comet, 458 reported here for the first time. we present methodology that builds upon our previous search on the first 4 yr of data. all images were reprocessed with an optimized detection pipeline that leads to an average completeness gain of 0.47 mag per exposure, as well as improved transient catalog production and algorithms for linkage of detections into orbits. all objects were verified by visual inspection and by the "sub-threshold significance," the signal-to-noise ratio in the stack of images in which its presence is indicated by the orbit, but no detection was reported. this yields a pure catalog complete to r ≈ 23.8 mag and distances 29 < d < 2500 au. the tnos have minimum (median) of 7 (12) nights' detections and arcs of 1.1 (4.2) yr, and will have grizy magnitudes available in a further publication. we present software for simulating our observational biases for comparisons of models to our detections. initial inferences demonstrating the catalog's statistical power are: the data are inconsistent with the cfeps-l7 model for the classical kuiper belt; the 16 "extreme" tnos (a > 150 au, q > 30 au) are consistent with the null hypothesis of azimuthal isotropy; and nonresonant tnos with q > 38 au, a > 50 au show a significant tendency to be sunward of major mean-motion resonances. | a search of the full six years of the dark energy survey for outer solar system objects |
orbiting an m dwarf 12 pc away, the transiting exoplanet gj 1132b is a prime target for transmission spectroscopy. with a mass of 1.7 m ⊕ and radius of 1.1 r ⊕, gj 1132b's bulk density indicates that this planet is rocky. yet with an equilibrium temperature of 580 k, gj 1132b may still retain some semblance of an atmosphere. understanding whether this atmosphere exists and its composition will be vital for understanding how the atmospheres of terrestrial planets orbiting m dwarfs evolve. we observe five transits of gj 1132b with the wide field camera 3 (wfc3) on the hubble space telescope (hst). we find a featureless transmission spectrum from 1.1 to 1.7 μm, ruling out cloud-free atmospheres with metallicities <300× solar with >4.8σ confidence. we combine our wfc3 results with transit depths from tess and archival broadband and spectroscopic observations to find a featureless spectrum across 0.7 to 4.5 μm. gj 1132b therefore has a high mean molecular weight atmosphere, possesses a high-altitude aerosol layer, or has effectively no atmosphere. higher-precision observations are required in order to differentiate between these possibilities. we explore the impact of hot and cold starspots on the observed transmission spectrum gj 1132b, quantifying the amplitude of spot-induced transit depth features. using a simple poisson model, we estimate spot temperature contrasts, spot covering fractions, and spot sizes for gj 1132. these limits, as well as the modeling framework, may be useful for future observations of gj 1132b or other planets transiting similarly inactive m dwarfs. | the featureless hst/wfc3 transmission spectrum of the rocky exoplanet gj 1132b: no evidence for a cloud-free primordial atmosphere and constraints on starspot contamination |
the he i λ10833 å triplet is a powerful tool for characterising the upper atmosphere of exoplanets and tracing possible mass loss. here, we analysed one transit of gj 1214 b observed with the carmenes high-resolution spectrograph to study its atmosphere via transmission spectroscopy around the he i triplet. although previous studies using lower resolution instruments have reported non-detections of he i in the atmosphere of gj 1214 b, we report here the first potential detection. we reconcile the conflicting results arguing that previous transit observations did not present good opportunities for the detection of he i, due to telluric h2o absorption and oh emission contamination. we simulated those earlier observations, and show evidence that the planetary signal was contaminated. from our single non-telluric-contaminated transit, we determined an excess absorption of 2.10−0.50+0.45% (4.6 σ) with a full width at half maximum (fwhm) of 1.30−0.25+0.30 å. the detection of he i is statistically significant at the 4.6 σ level, but repeatability of the detection could not be confirmed due to the availability of only one transit. by applying a hydrodynamical model and assuming an h/he composition of 98/2, we found that gj 1214 b would undergo hydrodynamic escape in the photon-limited regime, losing its primary atmosphere with a mass-loss rate of (1.5-18) × 1010 g s−1 and an outflow temperature in the range of 2900-4400 k. further high-resolution follow-up observations of gj 1214 b are needed to confirm and fully characterise the detection of an extended atmosphere surrounding gj 1214 b. if confirmed, this would be strong evidence that this planet has a primordial atmosphere accreted from the original planetary nebula. despite previous intensive observations from space- and ground-based observatories, our he i excess absorption is the first tentative detection of a chemical species in the atmosphere of this benchmark sub-neptune planet. | a tentative detection of he i in the atmosphere of gj 1214 b |
the young massive ob association cygnus ob2, in the cygnus x complex, is the closest (~1400 pc) star-forming region to the sun hosting thousands of young low-mass stars and up to 1000 ob stars, among which are some of the most massive stars known in our galaxy. this region holds great importance for several fields of modern astrophysics, such as the study of the physical properties of massive and young low-mass stars and the feedback provided by massive stars on star and planet formation processes. cyg ob2 has been recently observed with chandra/acis-i as part of the 1.08 ms chandra cygnus ob2 legacy project. this survey detected 7924 x-ray sources in a square degree area centered on cyg ob2. since a proper classification and study of the observed x-ray sources also requires the analysis of their optical and infrared counterparts, we combined a large and deep set of optical and infrared catalogs available for this region with our new x-ray catalog. in this paper we describe the matching procedure and present the combined catalog containing 5703 sources. we also briefly discuss the nature of the x-ray sources with optical and infrared counterparts using their position in the color-magnitude and color-color diagrams. | optical and infrared counterparts of the x-ray sources detected in the chandra cygnus ob2 legacy survey |
ultra-hot jupiters offer interesting prospects for expanding our theories on dynamical evolution and the properties of extremely irradiated atmospheres. in this context, we present the analysis of new optical spectroscopy for the transiting ultra-hot jupiter wasp-121b. we first refine the orbital properties of wasp-121b, which is on a nearly polar (obliquity ψnorth = 88.1 ± 0.25° or ψsouth = 91.11 ± 0.20°) orbit, and exclude a high differential rotation for its fast-rotating (p < 1.13 days), highly inclined (i⋆north = 8.1-2.6+3.0° or i⋆south = 171.9-3.4+2.5°) star. we then present a new method that exploits the reloaded rossiter-mclaughlin technique to separate the contribution of the planetary atmosphere and of the spectrum of the stellar surface along the transit chord. its application to harps transit spectroscopy of wasp-121b reveals the absorption signature from metals, likely atomic iron, in the planet atmospheric limb. the width of the signal (14.3 ± 1.2 km s-1) can be explained by the rotation of the tidally locked planet. its blueshift (-5.2 ± 0.5 km s-1) could trace strong winds from the dayside to the nightside, or the anisotropic expansion of the planetary thermosphere. the custom ccf mask built for wasp-121, and the eulercam lightcurves are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/635/a205 based on observations made at eso 3.6 m telescope (la silla, chile) under eso programme 100.c-0750. | hot exoplanet atmospheres resolved with transit spectroscopy (hearts). iii. atmospheric structure of the misaligned ultra-hot jupiter wasp-121b |
saturn's moon, enceladus, is a geologically active waterworld. the prevailing paradigm is that there is a subsurface ocean that erupts to the surface, which leads to the formation of a plume of vapor and ice above the south polar region. the chemistry of the ocean is just beginning to be understood, but is of profound geochemical and astrobiological interest. here, we determine the ph of the ocean using a thermodynamic model of carbonate speciation. observational data from the cassini spacecraft are used to make a chemical model of ocean water on enceladus. the model suggests that enceladus' ocean is a na-cl-co3 solution with an alkaline ph of ∼11-12. the dominance of aqueous nacl is a feature that enceladus' ocean shares with terrestrial seawater, but the ubiquity of dissolved na2co3 suggests that soda lakes are more analogous to the enceladus ocean. the high ph implies that the hydroxide ion should be relatively abundant, while divalent metals should be present at low concentrations owing to buffering by carbonates and phyllosilicates on the ocean floor. carboxyl groups in dissolved organic species would be negatively charged, while amino groups would exist predominately in the neutral form. knowledge of the ph improves our understanding of geochemical processes in enceladus' ocean. the high ph is interpreted to be a key consequence of serpentinization of chondritic rock, as predicted by prior geochemical reaction path models; although degassing of co2 from the ocean may also play a role depending on the efficiency of mixing processes in the ocean. serpentinization leads to the generation of h2, a geochemical fuel that can support both abiotic and biological synthesis of organic molecules such as those that have been detected in enceladus' plume. serpentinization and h2 generation should have occurred on enceladus, like on the parent bodies of aqueously altered meteorites; but it is unknown whether these critical processes are still taking place, or if enceladus' rocky core has been completely altered by past hydrothermal activity. the presence of native h2 in the plume would provide strong evidence for contemporary aqueous alteration that replenishes this source of energy for possible life. the high ph also suggests that the delivery of strong oxidants from the surface to the ocean has not been significant (otherwise, sulfuric acid would be produced), which would be consistent with geophysical models of episodic resurfacing activity on enceladus. this paper represents an expansion of chemical oceanography to an "ocean planet" beyond earth. | the ph of enceladus' ocean |
we apply the automated anomalyfinder algorithm of paper i to 2018-2019 light curves from the ≃13 deg2 covered by the six kmtnet prime fields, with cadences γ ≥ 2 hr-1. we find a total of 11 planets with mass ratios q < 2 × 10-4, including 6 newly discovered planets, 1 planet that was reported in paper i, and recovery of 4 previously discovered planets. one of the new planets, ogle-2018-blg-0977lb, is in a planetary caustic event, while the other five (ogle-2018-blg-0506lb, ogle-2018-blg-0516lb, ogle-2019-blg-1492lb, kmt-2019-blg-0253, and kmt-2019-blg-0953) are revealed by a "dip" in the light curve as the source crosses the host-planet axis on the opposite side of the planet. these subtle signals were missed in previous by-eye searches. the planet-host separations (scaled to the einstein radius), s, and planet-host mass ratios, q, are, respectively, (s, q × 105) = (0.88, 4.1), (0.96 ± 0.10, 8.3), (0.94 ± 0.07, 13), (0.97 ± 0.07, 18), (0.97 ± 0.04, 4.1), and (0.74, 18), where the " ± " indicates a discrete degeneracy. the 11 planets are spread out over the range $-5\lt \mathrm{log}q\lt -3.7$ . together with the two planets previously reported with q ~ 10-5 from the 2018-2019 nonprime kmt fields, this result suggests that planets toward the bottom of this mass-ratio range may be more common than previously believed. | systematic kmtnet planetary anomaly search. ii. six new q < 2 × 10-4 mass-ratio planets |
we present the discovery of hd 221416 b, the first transiting planet identified by the transiting exoplanet survey satellite (tess) for which asteroseismology of the host star is possible. hd 221416 b (hip 116158, toi-197) is a bright (v = 8.2 mag), spectroscopically classified subgiant that oscillates with an average frequency of about 430 μhz and displays a clear signature of mixed modes. the oscillation amplitude confirms that the redder tess bandpass compared to kepler has a small effect on the oscillations, supporting the expected yield of thousands of solar-like oscillators with tess 2 minute cadence observations. asteroseismic modeling yields a robust determination of the host star radius (r ⋆ = 2.943 ± 0.064 r ⊙), mass (m ⋆ = 1.212 ± 0.074 m ⊙), and age (4.9 ± 1.1 gyr), and demonstrates that it has just started ascending the red-giant branch. combining asteroseismology with transit modeling and radial-velocity observations, we show that the planet is a “hot saturn” (r p = 9.17 ± 0.33 r ⊕) with an orbital period of ∼14.3 days, irradiance of f = 343 ± 24 f ⊕, and moderate mass (m p = 60.5 ± 5.7 m ⊕) and density (ρ p = 0.431 ± 0.062 g cm-3). the properties of hd 221416 b show that the host-star metallicity-planet mass correlation found in sub-saturns (4-8 r ⊕) does not extend to larger radii, indicating that planets in the transition between sub-saturns and jupiters follow a relatively narrow range of densities. with a density measured to ∼15%, hd 221416 b is one of the best characterized saturn-size planets to date, augmenting the small number of known transiting planets around evolved stars and demonstrating the power of tess to characterize exoplanets and their host stars using asteroseismology. | a hot saturn orbiting an oscillating late subgiant discovered by tess |
observations of young open clusters (ocs) show a bimodal distribution of rotation periods that has been difficult to explain with existing stellar spin-down models. detailed magnetohydrodynamic (mhd) stellar wind simulations have demonstrated that surface magnetic field morphology has a strong influence on wind-driven angular momentum loss. observations suggest that faster rotating stars store a larger fraction of their magnetic flux in higher-order multipolar components of the magnetic field. in this work, we present an entirely predictive new model for stellar spin-down that accounts for the stellar surface magnetic field configuration. we show how a magnetic complexity that evolves from complex toward simple configurations as a star spins down can explain the salient features of stellar rotation evolution, including the bimodal distribution of both slow and fast rotators seen in young ocs. title inspired by c. l. davis phd thesis revolution evolution: tracing angular momentum during star and planetary system formation, st. andrews university. | the revolution revolution: magnetic morphology driven spin-down |
jupiter, the fascinating largest planet in the solar system, has been visited by nine spacecraft, which have collected a significant amount of data about jovian properties. in this paper, we show that one type of the in situ measurements on the relativistic electron fluxes could be used to probe dark matter (dm) and dark mediator between the dark sector and our visible world. jupiter, with its immense weight and cool core, could be an ideal capturer for dm with masses around the gev scale. the captured dm particles could annihilate into long-lived dark mediators such as dark photons, which subsequently decay into electrons and positrons outside jupiter. the charged particles, trapped by the jovian magnetic field, have been measured in jupiter missions such as the galileo probe and the juno orbiter. we use the data available to set upper bounds on the cross section of dm scattering off nucleons, σχn, for dark mediators with lifetime of order o (0.1-1) s. the results show that data from jupiter missions already probe regions in the parameter space un- or under-explored by existing dm searches, e.g., constrain σχn of order (10−41-10−39) cm2 for 1 gev dm dominantly annihilating into e+e− through dark mediators. this study serves as an example and an initial step to explore the full physics potential of the large planetary datasets from jupiter missions. we also outline several other potential directions related to secondary products of electrons, positron signals and solar axions. | jupiter missions as probes of dark matter |
transmission spectroscopy is one of the premier methods used to probe the temperature, composition, and cloud properties of exoplanet atmospheres. recent studies have demonstrated that the multidimensional nature of exoplanet atmospheres-due to nonuniformities across the day-night transition and between the morning and evening terminators-can strongly influence transmission spectra. however, the computational demands of 3d radiative-transfer techniques have precluded their usage within atmospheric retrievals. here we introduce trident, a new 3d radiative-transfer model which rapidly computes transmission spectra of exoplanet atmospheres with day-night, morning-evening, and vertical variations in temperature, chemical abundances, and cloud properties. we also derive a general equation for transmission spectra, accounting for 3d atmospheres, refraction, multiple scattering, ingress/egress, grazing transits, stellar heterogeneities, and nightside thermal emission. after introducing trident's linear-algebra-based approach to 3d radiative transfer, we propose new parametric prescriptions for 3d temperature and abundance profiles and 3d clouds. we show that multidimensional transmission spectra exhibit two significant observational signatures: (i) day-night composition gradients alter the relative amplitudes of absorption features; and (ii) morning-evening composition gradients distort the peak-to-wing contrast of absorption features. finally, we demonstrate that these signatures of multidimensional atmospheres incur residuals >100 ppm compared to 1d models, rendering them potentially detectable with the james webb space telescope. trident's rapid radiative transfer, coupled with parametric multidimensional atmospheres, unlocks the final barrier to 3d atmospheric retrievals. | trident: a rapid 3d radiative-transfer model for exoplanet transmission spectra |
in exoplanetary systems, the interaction between the central star and the planet can trigger auroral radio emission (are), due to the electron cyclotron maser mechanism. the high brightness temperature of this emission makes it visible at large distances, opening new opportunities to study exoplanets and to search for favourable conditions for the development of extra-terrestrial life, as magnetic fields act as a shield that protects life against external particles and influences the evolution of the planetary atmospheres. in the last few years, we started an observational campaign to observe a sample of nearby m-type stars known to host exoplanets with the aim to detect are. we observed yz ceti with the upgraded giant metrewave radio telescope (ugmrt) in band 4 (550-900 mhz) nine times over a period of five months. we detected radio emission four times, two of which with high degree of circular polarization. with statistical considerations we exclude the possibility of flares due to stellar magnetic activity. instead, when folding the detections to the orbital phase of the closest planet yz cet b, they are at positions where we would expect are due to star-planet interaction (spi) in sub-alfvenic regime. with a degree of confidence higher than 4.37 sigma, yz cet is the first extrasolar systems with confirmed spi at radio wavelengths. modelling the are, we estimate a magnetic field for the star of about 2.4 kg and we find that the planet must have a magnetosphere. the lower limit for the polar magnetic field of the planet is 0.4 g. | star-planet interaction at radio wavelengths in yz ceti: inferring planetary magnetic field |
rovers and landers on mars have experienced local, regional, and planetary-scale dust storms. however, in situ documentation of active lifting within storms has remained elusive. over 5-11 january 2022 (ls 153°-156°), a dust storm passed over the perseverance rover site. peak visible optical depth was ∼2, and visibility across the crater was briefly reduced. pressure amplitudes and temperatures responded to the storm. winds up to 20 m s-1 rotated around the site before the wind sensor was damaged. the rover imaged 21 dust-lifting events—gusts and dust devils—in one 25-min period, and at least three events mobilized sediment near the rover. rover tracks and drill cuttings were extensively modified, and debris was moved onto the rover deck. migration of small ripples was seen, but there was no large-scale change in undisturbed areas. this work presents an overview of observations and initial results from the study of the storm. | dust, sand, and winds within an active martian storm in jezero crater |
the primary objective of this study is to investigate the formation and evolution mechanism of the regional haze in beijing by analyzing the process of a severe haze episode that occurredfrom1 to 31 january 2013. the mass concentration of pm2.5 and its chemical components were simultaneously measured at the beijing urban atmospheric environmental monitoring station. the haze was characterized by a high frequency, a long duration, a large influential region and an extremely high pm2.5 values (> 500 μg/m3). the primary factors driving the haze formation were stationary atmospheric flows (in both vertical and horizontal directions), while a temperature inversion, a lower planetary boundary layer and a higher rh accelerated the formation of the regional haze. in one incident, the temperature inversion layer occurred at a height of 130 m above ground level, which prevented the air pollutants from being dispersed vertically. the regional transport of pollutants also played an important role in the formation of the haze. wind from the south of beijing increased from 58% in january 2012 to 63% in january 2013. because the area to the south of beijing is characterized by high industrial development, the unusual wind direction favored the regional transport of pollutants and severely exacerbated the haze. so42-, no3- and nh4+ are the three major water-soluble ions that contributed to the formation of the haze. the high variability in cl- and k+ indicated that large quantities of coal combustion and biomass burning occurred during the haze. | formation mechanism of continuous extreme haze episodes in the megacity beijing, china, in january 2013 |
we present an open-source retrieval code named helios-retrieval, designed to obtain chemical abundances and temperature-pressure profiles by inverting the measured spectra of exoplanetary atmospheres. in our forward model, we use an exact solution of the radiative transfer equation, in the pure absorption limit, which allows us to analytically integrate over all of the outgoing rays. two chemistry models are considered: unconstrained chemistry and equilibrium chemistry (enforced via analytical formulae). the nested sampling algorithm allows us to formally implement occam’s razor based on a comparison of the bayesian evidence between models. we perform a retrieval analysis on the measured spectra of the four hr 8799 directly imaged exoplanets. chemical equilibrium is disfavored for hr 8799b and c. we find supersolar c/h and o/h values for the outer hr 8799b and c exoplanets, while the inner hr 8799d and e exoplanets have a range of c/h and o/h values. the c/o values range from being superstellar for hr 8799b to being consistent with stellar for hr 8799c and being substellar for hr 8799d and e. if these retrieved properties are representative of the bulk compositions of the exoplanets, then they are inconsistent with formation via gravitational instability (without late-time accretion) and consistent with a core accretion scenario in which late-time accretion of ices occurred differently for the inner and outer exoplanets. for hr 8799e, we find that spectroscopy in the k band is crucial for constraining c/o and c/h. helios-retrieval is publicly available as part of the exoclimes simulation platform (http://www.exoclime.org). | helios-retrieval: an open-source, nested sampling atmospheric retrieval code; application to the hr 8799 exoplanets and inferred constraints for planet formation |
context. the characterisation of the atmosphere of exoplanets is one of the main goals of exoplanet science in the coming decades.aims: we investigate the detectability of atmospheric spectral features of earth-like planets in the habitable zone (hz) around m dwarfs with the future james webb space telescope (jwst).methods: we used a coupled 1d climate-chemistry-model to simulate the influence of a range of observed and modelled m-dwarf spectra on earth-like planets. the simulated atmospheres served as input for the calculation of the transmission spectra of the hypothetical planets, using a line-by-line spectral radiative transfer model. to investigate the spectroscopic detectability of absorption bands with jwst we further developed a signal-to-noise ratio (s/n) model and applied it to our transmission spectra.results: high abundances of methane (ch4) and water (h2o) in the atmosphere of earth-like planets around mid to late m dwarfs increase the detectability of the corresponding spectral features compared to early m-dwarf planets. increased temperatures in the middle atmosphere of mid- to late-type m-dwarf planets expand the atmosphere and further increase the detectability of absorption bands. to detect ch4, h2o, and carbon dioxide (co2) in the atmosphere of an earth-like planet around a mid to late m dwarf observing only one transit with jwst could be enough up to a distance of 4 pc and less than ten transits up to a distance of 10 pc. as a consequence of saturation limits of jwst and less pronounced absorption bands, the detection of spectral features of hypothetical earth-like planets around most early m dwarfs would require more than ten transits. we identify 276 existing m dwarfs (including gj 1132, trappist-1, gj 1214, and lhs 1140) around which atmospheric absorption features of hypothetical earth-like planets could be detected by co-adding just a few transits.conclusions: the tess satellite will likely find new transiting terrestrial planets within 15 pc from the earth. we show that using transmission spectroscopy, jwst could provide enough precision to be able to partly characterise the atmosphere of tess findings with an earth-like composition around mid to late m dwarfs. the data from top fig. 6 are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/624/a49 | detectability of atmospheric features of earth-like planets in the habitable zone around m dwarfs |
in this study, the heavy precipitation event on 01 december 2015 over chennai located on the southeast coast of india was simulated using the weather research and forecast (wrf) model. a series of simulations were conducted using explicit convection and varying the planetary boundary layer (pbl) parameterization schemes. the model results were compared with available surface, satellite and doppler weather radar observations. simulations indicate strong, sustained moist convection associated with development of a mesoscale upper air cyclonic circulation, during the passage of a synoptic scale low-pressure trough caused heavy rainfall over chennai and its surroundings. results suggest that veering of wind with height associated with strong wind shear in the layer 800-400 hpa together with dry air advection facilitated development of instability and initiation of convection. the 1-km domain using explicit convection improved the prediction of rainfall intensity of about 450 mm and its distribution. the pbl physics strongly influenced the rainfall prediction by changing the location of upper air circulation, energy transport, moisture convergence and intensity of convection in the schemes ysu, myj and mynn. all the simulations underestimated the first spell of the heavy rainfall. while ysu and myj schemes grossly underestimated the rainfall and dislocated the area of maximum rainfall, the higher order mynn scheme simulated the rainfall pattern in better agreement with observations. the mynn showed lesser mixing and simulated more humid boundary layer, higher convective available potential energy (cape) and stronger winds at mid-troposphere than did the other schemes. the mynn also realistically simulated the location of upper air cyclonic flow and various dynamic and thermodynamic features. consequently it simulated stronger moisture convergence and higher precipitation. | simulation of an extreme heavy rainfall event over chennai, india using wrf: sensitivity to grid resolution and boundary layer physics |
we use a 3-d general circulation model to compare the primitive martian hydrological cycle in "warm and wet" and "cold and icy" scenarios. in the warm and wet scenario, an anomalously high solar flux or intense greenhouse warming artificially added to the climate model are required to maintain warm conditions and an ice-free northern ocean. precipitation shows strong surface variations, with high rates around hellas basin and west of tharsis but low rates around margaritifer sinus (where the observed valley network drainage density is nonetheless high). in the cold and icy scenario, snow migration is a function of both obliquity and surface pressure, and limited episodic melting is possible through combinations of seasonal, volcanic, and impact forcing. at surface pressures above those required to avoid atmospheric collapse (∼0.5 bar) and moderate to high obliquity, snow is transported to the equatorial highland regions where the concentration of valley networks is highest. snow accumulation in the aeolis quadrangle is high, indicating an ice-free northern ocean is not required to supply water to gale crater. at lower surface pressures and obliquities, both h2o and co2 are trapped as ice at the poles and the equatorial regions become extremely dry. the valley network distribution is positively correlated with snow accumulation produced by the cold and icy simulation at 41.8° obliquity but uncorrelated with precipitation produced by the warm and wet simulation. because our simulations make specific predictions for precipitation patterns under different climate scenarios, they motivate future targeted geological studies. | comparison of "warm and wet" and "cold and icy" scenarios for early mars in a 3-d climate model |
co is the most widely used gas tracer of protoplanetary disks. its abundance is usually assumed to be an interstellar ratio throughout the warm molecular layer of the disk. but recent observations of low co gas abundance in many protoplanetary disks challenge our understanding of physical and chemical evolutions in disks. here we investigate the co abundance structures in four well-studied disks and compare their structures with predictions of chemical processing of co and transport of co ice-coated dust grains in disks. we use spatially resolved co isotopologue line observations and detailed thermo-chemical models to derive co abundance structures. we find that the co abundance varies with radius by an order of magnitude in these disks. we show that although chemical processes can efficiently reduce the total column of co gas within 1 myr under an ism level of cosmic-ray ionization rate, the depletion mostly occurs at the deep region of a disk. without sufficient vertical mixing, the surface layer is not depleted enough to reproduce the weak co emissions observed. the radial profiles of co depletion in three disks are qualitatively consistent with predictions of pebble formation, settling, and drifting in disks. but the dust evolution alone cannot fully explain the high depletion observed in some disks. these results suggest that dust evolution may play a significant role in transporting volatile materials and a coupled chemical-dynamical study is necessary to understand what raw materials are available for planet formation at different distances from the central star. | systematic variations of co gas abundance with radius in gas-rich protoplanetary disks |
coronal mass ejections (cmes) are huge expulsions of magnetized matter from the sun and stars, traversing space with speeds of millions of kilometres per hour. solar cmes can cause severe space weather disturbances and consumer power outages on earth, whereas stellar cmes may even pose a hazard to the habitability of exoplanets. although cmes ejected by our sun can be directly imaged by white-light coronagraphs, for stars this is not possible. so far, only a few candidates for stellar cme detections have been reported. here we demonstrate a different approach that is based on sudden dimmings in the extreme ultraviolet and x-ray emission caused by the cme mass loss. we report dimming detections associated with flares on cool stars, indicative of stellar cmes, and which are benchmarked by sun-as-a-star extreme ultraviolet measurements. this study paves the way for comprehensive detections and characterizations of cmes on stars, which are important factors in planetary habitability and stellar evolution. | indications of stellar coronal mass ejections through coronal dimmings |
the lidov-kozai (lk) mechanism plays an important role in the secular evolution of many hierarchical triple systems. the standard lk mechanism consists of large-amplitude oscillations in eccentricity and inclination of a binary subject to the quadrupole potential from an outer perturber. recent work has shown that when the octupole terms are included in the potential, the inner binary can reach more extreme eccentricities as well as undergo orientation flips. it is known that pericentre precessions due to short-range effects, such as general relativity and tidal and rotational distortions, can limit the growth of eccentricity and even suppress standard (quadrupolar) lk oscillations, but their effect on the octupole-level lk mechanism has not been fully explored. in this paper, we systematically study how these short-range forces affect the extreme orbital behaviour found in octupole lk cycles. in general, the influence of the octupole potential is confined to a range of initial mutual inclinations itot centred around 90° (when the inner binary mass ratio is ≪1), with this range expanding with increasing octupole strength. we find that, while the short-range forces do not change the width and location of this `window of influence', they impose a strict upper limit on the maximum achievable eccentricity. this limiting eccentricity can be calculated analytically, and its value holds even for strong octupole potential and for the general case of three comparable masses. short-range forces also affect orbital flips, progressively reducing the range of itot within which flips are possible as the intensity of these forces increases. | suppression of extreme orbital evolution in triple systems with short-range forces |
jets and outflows are ubiquitous in the process of formation of stars since outflow is intimately associated with accretion. free-free (thermal) radio continuum emission in the centimeter domain is associated with these jets. the emission is relatively weak and compact, and sensitive radio interferometers of high angular resolution are required to detect and study it. one of the key problems in the study of outflows is to determine how they are accelerated and collimated. observations in the cm range are most useful to trace the base of the ionized jets, close to the young central object and the inner parts of its accretion disk, where optical or near-ir imaging is made difficult by the high extinction present. radio recombination lines in jets (in combination with proper motions) should provide their 3d kinematics at very small scale (near their origin). future instruments such as the square kilometre array (ska) and the next generation very large array (ngvla) will be crucial to perform this kind of sensitive observations. thermal jets are associated with both high and low mass protostars and possibly even with objects in the substellar domain. the ionizing mechanism of these radio jets appears to be related to shocks in the associated outflows, as suggested by the observed correlation between the centimeter luminosity and the outflow momentum rate. from this correlation and that of the centimeter luminosity with the bolometric luminosity of the system it will be possible to discriminate between unresolved hii regions and jets, and to infer additional physical properties of the embedded objects. some jets associated with young stellar objects (ysos) show indications of non-thermal emission (negative spectral indices) in part of their lobes. linearly polarized synchrotron emission has been found in the jet of hh 80-81, allowing one to measure the direction and intensity of the jet magnetic field, a key ingredient to determine the collimation and ejection mechanisms. as only a fraction of the emission is polarized, very sensitive observations such as those that will be feasible with the interferometers previously mentioned are required to perform studies in a large sample of sources. jets are present in many kinds of astrophysical scenarios. characterizing radio jets in ysos, where thermal emission allows one to determine their physical conditions in a reliable way, would also be useful in understanding acceleration and collimation mechanisms in all kinds of astrophysical jets, such as those associated with stellar and supermassive black holes and planetary nebulae. | radio jets from young stellar objects |
the large uv/optical/infrared surveyor (luvoir) mission is one of four decadal survey mission concepts studied by nasa in preparation for the us national academies' astro2020 decadal survey. this observatory has the major goal of characterizing a wide range of exoplanets, including those that might be habitable -- or even inhabited. it would simultaneously enable a great leap forward in a broad range of astrophysics -- from the epoch of reionization, through galaxy formation and evolution, to star and planet formation. powerful remote sensing observations of solar system bodies will also be possible. this interim report on the luvoir study presents the scientific motivations and goals of the mission concept, the preliminary and partial engineering design, and technology development information. | the luvoir mission concept study interim report |
the orbital distribution of trans-neptunian objects provides strong evidence for the radial migration of neptune1,2. the outer planets' orbits are thought to have become unstable during the early stages3, with jupiter having scattering encounters with a neptune-class planet4. as a consequence, jupiter jumped inwards by a fraction of an au, as required from inner solar system constraints5,6, and obtained its current orbital eccentricity. the timing of these events is often linked to the lunar late heavy bombardment that ended 700 myr after the dispersal of the protosolar nebula (t0)7,8. here, we show instead that planetary migration started shortly after t0. such early migration is inferred from the survival of the patroclus-menoetius binary jupiter trojan9. the binary formed at t ≲ t010,11 within a massive planetesimal disk once located beyond neptune12,13. the longer the binary stayed in the disk, the greater the likelihood that collisions would strip its components from one another. the simulations of its survival indicate that the disk had to have been dispersed by migrating planets within ≲100 myr of t0. this constraint implies that the planetary migration is unrelated to the formation of the youngest lunar basins. | evidence for very early migration of the solar system planets from the patroclus-menoetius binary jupiter trojan |
we present a new volume-limited sample of l0-t8 dwarfs out to 25 pc defined entirely by parallaxes, using our recent measurements from ukirt/wfcam along with gaia dr2 and literature parallaxes. with 369 members, our sample is the largest parallax-defined volume-limited sample of l and t dwarfs to date, yielding the most precise space densities for such objects. we find the local l0-t8 dwarf population includes $5.5 \% \pm 1.2 \% $ young objects (≲200 myr) and $2.6 \% \pm 1.6 \% $ subdwarfs, as expected from recent studies favoring representative ages ≲4 gyr for the ultracool field population. this is also the first volume-limited sample to comprehensively map the transition from l to t dwarfs (spectral types ≈l8-t4). after removing binaries, we identify a previously unrecognized, statistically significant (>4.4σ) gap ≈0.5 mag wide in ${(j-k)}_{\mathrm{mko}}$ colors in the l/t transition, i.e., a lack of such objects in our volume-limited sample, implying a rapid phase of atmospheric evolution. in contrast, the most successful models of the l/t transition to date—the "hybrid" models of saumon & marley—predict a pileup of objects at the same colors where we find a deficit, demonstrating the challenge of modeling the atmospheres of cooling brown dwarfs. our sample illustrates the insights to come from even larger parallax-selected samples from the upcoming legacy survey of space and time by the vera rubin obsevatory. | a volume-limited sample of ultracool dwarfs. i. construction, space density, and a gap in the l/t transition |
this review introduces physical processes in protoplanetary disks relevant to accretion and the initial stages of planet formation. after a brief overview of the observational context, i introduce the elementary theory of disk structure and evolution, review the gas-phase physics of angular momentum transport through turbulence and disk winds, and discuss possible origins for the episodic accretion observed in young stellar objects. turning to solids, i review the evolution of single particles under aerodynamic forces, and describe the conditions necessary for the development of collective gas-particle instabilities. observations show that disks can exhibit pronounced large-scale structure, and i discuss the types of structures that may form from gas and particle interactions at ice lines, vortices and zonal flows, prior to the formation of large planetary bodies. i conclude with disk dispersal. | physical processes in protoplanetary disks |
the minerva-australis telescope array is a facility dedicated to the follow-up, confirmation, characterization, and mass measurement of planets orbiting bright stars discovered by the transiting exoplanet survey satellite (tess)—a category in which it is almost unique in the southern hemisphere. it is located at the university of southern queensland’s mount kent observatory near toowoomba, australia. its flexible design enables multiple 0.7 m robotic telescopes to be used both in combination, and independently, for high-resolution spectroscopy and precision photometry of tess transit planet candidates. minerva-australis also enables complementary studies of exoplanet spin-orbit alignments via doppler observations of the rossiter-mclaughlin effect, radial velocity searches for nontransiting planets, planet searches using transit timing variations, and ephemeris refinement for tess planets. in this first paper, we describe the design, photometric instrumentation, software, and science goals of minerva-australis, and note key differences from its northern hemisphere counterpart, the minerva array. we use recent transit observations of four planets, wasp-2b, wasp-44b, wasp-45b, and hd 189733b, to demonstrate the photometric capabilities of minerva-australis. | minerva-australis. i. design, commissioning, and first photometric results |
studying the spatiotemporal variations of the urban heat island (uhi) effect and its cause is important towards understanding urban climate change, planning and green development, and disaster mitigation. in this paper, by using surface observations and reanalysis data with objective classification of synoptic weather patterns (swps), we analyze the associations between canopy uhi intensity (cuhi) and swps in the planetary boundary layer (pbl) and their potential drivers during wintertime of the period 2012-2017. six dominant types of swp are identified as follows: in the case of types 3, 4, and 6, weak high-pressure systems exist to the south of beijing, resulting in weak southerly winds with low pbl height, large cloud coverage and high relative humidity (rh). these conditions are generally conducive to a strengthening of the cuhii. in contrast, under types 1, 2, and 5, high-pressure systems are located to the northwest of beijing, and the associated strong northwesterly flows of dry and cold air strengthen the boundary layer mixing process, resulting in large wind speed and low rh. this is conducive to a weakening of the cuhii. in general, our work reveals the impacts of swps on the strength of cuhii mainly via the modulation of local weather conditions at diurnal and interannual scales, while spatial pattern of cuhii is largely dominated by local climate zones. our findings have implications for cuhii forecasts, as well as impact assessments and policymaking in the context of uhi-related energy conservation in winter over high-density urban areas on the synoptic scale. | modulation of wintertime canopy urban heat island (cuhi) intensity in beijing by synoptic weather pattern in planetary boundary layer |
existing hypotheses for the dynamical dependence of tropical cyclone genesis and size on latitude depend principally on the coriolis parameter f. these hypotheses are tested via dynamical aquaplanet experiments with uniform thermal forcing in which planetary rotation rate and planetary radius are varied relative to earth values; the control simulation is also compared to a present-day earth simulation. storm genesis rate collapses to a quasi-universal dependence on f that attains its maximum at the critical latitude, where the inverse-f scale and rhines scale are equal. minimum genesis distance from the equator is set by the equatorial rhines (or deformation) scale and not by a minimum value of f. outer storm size qualitatively follows the smaller of the two length scales, including a slow increase with latitude equatorward of 45° in the control simulation, similar to the earth simulation. the latitude of peak size scales with the critical latitude for varying planetary radius but not rotation rate, possibly because of the dependence of genesis specifically on f. the latitudes of peak size and peak packing density scale closely together. results suggest that temporal effects and interstorm interaction may be significant for size dynamics. more generally, the critical latitude separates two regimes: 1) a mixed wave-cyclone equatorial belt, where wave effects are strong and the rhines scale likely limits storm size, and 2) a cyclone-filled polar cap, where wave effects are weak and cyclones persist. the large-planet limit predicts a world nearly covered with long-lived storms, equivalent to the f plane. overall, spherical geometry is likely important for understanding tropical cyclone genesis and size on earthlike planets. | dynamical aquaplanet experiments with uniform thermal forcing: system dynamics and implications for tropical cyclone genesis and size |
the habitable zone (hz) is the circular region around a star(s) where standing bodies of water could exist on the surface of a rocky planet. space missions employ the hz to select promising targets for follow-up habitability assessment. the classical hz definition assumes that the most important greenhouse gases for habitable planets orbiting main-sequence stars are co2 and h2o. although the classical hz is an effective navigational tool, recent hz formulations demonstrate that it cannot thoroughly capture the diversity of habitable exoplanets. here, i review the planetary and stellar processes considered in both classical and newer hz formulations. supplementing the classical hz with additional considerations from these newer formulations improves our capability to filter out worlds that are unlikely to host life. such improved hz tools will be necessary for current and upcoming missions aiming to detect and characterize potentially habitable exoplanets. | a more comprehensive habitable zone for finding life on other planets |
this paper presents a novel signal processing scheme by combining an improved vold-kalman filter and the multi-scale sample entropy (ivkf-msse) for planetary gearboxes under non-stationary working conditions. in this scheme, we propose a method based on the characteristic frequency ratio (cfr) to select the vkf bandwidth. first, a cfr is adopted to select a vkf bandwidth with the largest cfr value as the optimal vkf bandwidth. second, ivkf is used to extract fault-induced information under time-varying speed conditions. because an optimal bandwidth is used in vkf, the feature extraction capability of vkf is enhanced. then, the msse is applied to extract gearbox fault features. after that, the laplacian score (ls) approach is introduced to refine the fault features by sorting the scale factors. at the end, the selected features are fed into the least square support vector machine (lssvm) for effective fault pattern identification. simulation and experimental vibration signals are employed to evaluate the effectiveness of the proposed method. results show that the proposed method outperforms the auto-regressive ar-msse, vkf-msse and eemd-msse in identifying fault types of planetary gearboxes. | a fault diagnosis method for planetary gearboxes under non-stationary working conditions using improved vold-kalman filter and multi-scale sample entropy |
we study how the interaction between the streaming instability (si) and intrinsic gas-phase turbulence affects planetesimal formation via gravitational collapse in protoplanetary disks. turbulence impedes the formation of particle clumps by acting as an effective turbulent diffusivity, but it can also promote planetesimal formation by concentrating solids, for example, in zonal flows. we quantify the effect of turbulent diffusivity using numerical simulations of the si in small local domains, forced with velocity perturbations that establish approximately kolmogorov-like turbulence. we find that planetesimal formation is suppressed by turbulence once velocity fluctuations exceed $\langle \delta {v}^{2}\rangle $ ≃ (10-3.5-10-3) ${c}_{s}^{2}$ . turbulence whose strength is just below the threshold reduces the rate at which solids are bound into clumps. our results suggest that the well-established turbulent thickening of the midplane solid layer is the primary mechanism by which turbulence influences planetesimal formation and that planetesimal formation requires a midplane solid-to-gas ratio ɛ ≳ 0.5. we also quantify the initial planetesimal mass function using a new clump-tracking method to determine each planetesimal mass shortly after collapse. for models in which planetesimals form, we show that the mass function is well described by a broken power law, whose parameters are robust to the inclusion and strength of imposed turbulence. turbulence in protoplanetary disks is likely to substantially exceed the threshold for planetesimal formation at radii where temperatures t ≳ 103 k lead to thermal ionization. planetesimal formation may therefore be unviable in the inner disk out to 2-3 times the dust sublimation radius. | turbulence regulates the rate of planetesimal formation via gravitational collapse |
we present wasp-43b climate simulations with deep wind jets (down to 700 bar) that are linked to retrograde (westward) flow at the equatorial day side for p < 0.1 bar. retrograde flow inhibits efficient eastward heat transport and naturally explains the small hotspot shift and large day-night-side gradient of wasp-43b (porb = prot = 0.8135 d) observed with spitzer. we find that deep wind jets are mainly associated with very fast rotations (prot = porb ≤ 1.5 d) which correspond to the rhines length smaller than 2 planetary radii. we also diagnose wave activity that likely gives rise to deviations from superrotation. further, we show that we can achieve full steady state in our climate simulations by imposing a deep forcing regime for p > 10 bar: convergence time-scale τconv = 106-108 s to a common adiabat, as well as linear drag at depth (p ≥ 200 bar), which mimics to first-order magnetic drag. lower boundary stability and the deep forcing assumptions were also tested with climate simulations for hd 209458b (porb = prot = 3.5 d). hd 209458b simulations always show shallow wind jets (never deeper than 100 bar) and unperturbed superrotation. if we impose a fast rotation (porb = prot = 0.8135 d), also the hd 209458b-like simulation shows equatorial retrograde flow at the day side. we conclude that the placement of the lower boundary at p = 200 bar is justified for slow rotators like hd 209458b, but we suggest that it has to be placed deeper for fast-rotating, dense hot jupiters (porb ≤ 1.5 d) like wasp-43b. our study highlights that the deep atmosphere may have a strong influence on the observable atmospheric flow in some hot jupiters. | equatorial retrograde flow in wasp-43b elicited by deep wind jets? |
we analyze the transmission and emission spectra of the ultra-hot jupiter wasp-76 b, observed with the g141 grism of the hubble space telescope's (hst) wide field camera 3 (wfc3). we reduce and fit the raw data for each observation using the open-source software iraclis before performing a fully bayesian retrieval using the publicly available analysis suite taurex 3. previous studies of the wfc3 transmission spectra of wasp-76 b found hints of titanium oxide (tio) and vanadium oxide (vo) or non-gray clouds. accounting for a fainter stellar companion to wasp-76, we reanalyze this data and show that removing the effects of this background star changes the slope of the spectrum, resulting in these visible absorbers no longer being detected, eliminating the need for a non-gray cloud model to adequately fit the data but maintaining the strong water feature previously seen. however, our analysis of the emission spectrum suggests the presence of tio and an atmospheric thermal inversion, along with a significant amount of water. given the brightness of the host star and the size of the atmospheric features, wasp-76 b is an excellent target for further characterization with hst, or with future facilities, to better understand the nature of its atmosphere, to confirm the presence of tio and to search for other optical absorbers. * ares: ariel retrieval of exoplanets school. | ares i: wasp-76 b, a tale of two hst spectra |
context. polarimetric imaging is one of the most effective techniques for high-contrast imaging and for the characterization of protoplanetary disks, and it has the potential of becoming instrumental in the characterization of exoplanets. the spectro-polarimetric high-contrast exoplanet research (sphere) instrument installed on the very large telescope (vlt) contains the infrared dual-band imager and spectrograph (irdis) with a dual-beam polarimetric imaging (dpi) mode, which offers the capability of obtaining linear polarization images at high contrast and resolution.aims: we aim to provide an overview of the polarimetric imaging mode of vlt/sphere/irdis and study its optical design to improve observing strategies and data reduction.methods: for h-band observations of tw hydrae, we compared two data reduction methods that correct for instrumental polarization effects in different ways: a minimization of the "noise" image (uϕ), and a correction method based on a polarimetric model that we have developed, as presented in paper ii of this study.results: we use observations of tw hydrae to illustrate the data reduction. in the images of the protoplanetary disk around this star, we detect variability in the polarized intensity and angle of linear polarization that depend on the pointing-dependent instrument configuration. we explain these variations as instrumental polarization effects and correct for these effects using our model-based correction method.conclusions: the polarimetric imaging mode of irdis has proven to be a very successful and productive high-contrast polarimetric imaging system. however, the instrument performance is strongly dependent on the specific instrument configuration. we suggest adjustments to future observing strategies to optimize polarimetric efficiency in field-tracking mode by avoiding unfavorable derotator angles. we recommend reducing on-sky data with the pipeline called irdap, which includes the model-based correction method (described in paper ii) to optimally account for the remaining telescope and instrumental polarization effects and to retrieve the true polarization state of the incident light. based on observations made with eso telescopes at the la silla paranal observatory under programme id 095.c-0273(d). | polarimetric imaging mode of vlt/sphere/irdis. i. description, data reduction, and observing strategy |
evidence for plumes of water on europa has previously been found using the hubble space telescope using two different observing techniques. roth et al. found line emission from the dissociation products of water. sparks et al. found evidence for off-limb continuum absorption as europa transited jupiter. here, we present a new transit observation of europa that shows a second event at the same location as a previous plume candidate from sparks et al., raising the possibility of a consistently active source of erupting material on europa. this conclusion is bolstered by comparison with a nighttime thermal image from the galileo photopolarimeter-radiometer that shows a thermal anomaly at the same location, within the uncertainties. the anomaly has the highest observed brightness temperature on the europa nightside. if heat flow from a subsurface liquid water reservoir causes the thermal anomaly, its depth is ≈1.8-2 km, under simple modeling assumptions, consistent with scenarios in which a liquid water reservoir has formed within a thick ice shell. models that favor thin regions within the ice shell that connect directly to the ocean, however, cannot be excluded, nor modifications to surface thermal inertia by subsurface activity. alternatively, vapor deposition surrounding an active vent could increase the thermal inertia of the surface and cause the thermal anomaly. this candidate plume region may offer a promising location for an initial characterization of europa’s internal water and ice and for seeking evidence of europa’s habitability. | active cryovolcanism on europa? |
context. the calar alto high-resolution search for m dwarfs with exo-earths with near-infrared and optical echelle spectrographs (carmenes) survey is searching for earth-like planets orbiting m dwarfs using the radial velocity method. studying the stellar activity of the target stars is important to avoid false planet detections and to improve our understanding of the atmospheres of late-type stars.aims: in this work we present measurements of activity indicators at visible and near-infrared wavelengths for 331 m dwarfs observed with carmenes. our aim is to identify the activity indicators that are most sensitive and easiest to measure, and the correlations among these indicators. we also wish to characterise their variability.methods: using a spectral subtraction technique, we measured pseudo-equivalent widths of the he i d3, hα, he i λ10833 å, and pa β lines, the na i d doublet, and the ca ii infrared triplet, which have a chromospheric component in active m dwarfs. in addition, we measured an index of the strength of two tio and two vo bands, which are formed in the photosphere. we also searched for periodicities in these activity indicators for all sample stars using generalised lomb-scargle periodograms.results: we find that the most slowly rotating stars of each spectral subtype have the strongest hα absorption. hα is correlated most strongly with he i d3, whereas na i d and the ca ii infrared triplet are also correlated with hα. he i λ10833 å and paβ show no clear correlations with the other indicators. the tio bands show an activity effect that does not appear in the vo bands. we find that the relative variations of hα and he i d3 are smaller for stars with higher activity levels, while this anti-correlation is weaker for na i d and the ca ii infrared triplet, and is absent for he i λ10833 å and paβ. periodic variation with the rotation period most commonly appears in the tio bands, hα, and in the ca ii infrared triplet. the full version of table a.1 is only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/623/a44 | the carmenes search for exoplanets around m dwarfs. activity indicators at visible and near-infrared wavelengths |
upcoming studies of extrasolar gas giants will give precise insights into the composition of planetary atmospheres, with the ultimate goal of linking it to the formation history of the planet. here, we investigate how drifting and evaporating pebbles that enrich the gas phase of the disk influence the chemical composition of growing and migrating gas giants. to achieve this goal, we perform semi-analytical 1d models of protoplanetary disks, including viscous evolution, pebble drift, and evaporation, to simulate the growth of planets from planetary embryos to jupiter-mass objects by the accretion of pebbles and gas while they migrate through the disk. the gas phase of the protoplanetary disk is enriched due to the evaporation of inward drifting pebbles crossing evaporation lines, leading to the accretion of large amounts of volatiles into the planetary atmosphere. as a consequence, gas-accreting planets are enriched in volatiles (c, o, n) compared to refractories (e.g., mg, si, fe) by up to a factor of 100, depending on the chemical species, its exact abundance and volatility, and the disk's viscosity. a simplified model for the formation of jupiter reveals that its nitrogen content can be explained by inward diffusing nitrogen-rich vapor, implying that jupiter did not need to form close to the n2 evaporation front as indicated by previous simulations. however, our model predicts an excessively low oxygen abundance for jupiter, implying either jupiter's migration across the water ice line (as in the grand tack scenario) or an additional accretion of solids into the atmosphere (which can also increase jupiter's carbon abundance, ultimately changing the planetary c/o ratio). the accretion of solids, on the other hand, will increase the refractory-to-volatile ratio in planetary atmospheres substantially. we thus conclude that the volatile-to-refractory ratio in planetary atmospheres can place a strong constraint on planet formation theories (in addition to elemental ratios), especially on the amount of solids accreted into atmospheres, making it an important target for future observations. | how drifting and evaporating pebbles shape giant planets. ii. volatiles and refractories in atmospheres |
ultrahot jupiters represent an exciting avenue for testing extreme physics and observing atmospheric circulation regimes not found in our solar system. their high temperatures result in thermally ionized particles embedded in atmospheric winds interacting with the planet's interior magnetic field by generating current and experiencing bulk lorentz force drag. previous treatments of magnetic drag in 3d general circulation models (gcms) of ultrahot jupiters have mostly been uniform drag timescales applied evenly throughout the planet, which neglects the strong spatial dependence of these magnetic effects. in this work, we apply our locally calculated active magnetic drag treatment in a gcm of the planet wasp-76b. we find the effects of this treatment to be most pronounced in the planet's upper atmosphere, where strong differences between the day and night side circulation are present. these circulation effects alter the resulting phase curves by reducing the hot spot offset and increasing the day-night flux contrast. we compare our models to spitzer phase curves, which imply a magnetic field of at least 3 g for the planet. we additionally contrast our results to uniform drag timescale models. this work highlights the need for more careful treatment of magnetic effects in atmospheric models of hot gas giants. | exploring the effects of active magnetic drag in a general circulation model of the ultrahot jupiter wasp-76b |
during the commissioning of jwst, the medium-resolution spectrometer (mrs) on the mid-infrared instrument (miri) observed the planetary nebula smp lmc 058 in the large magellanic cloud. the mrs was designed to provide medium resolution (r = λ/δλ) 3d spectroscopy in the whole miri range. smp lmc 058 is the only source observed in jwst commissioning that is both spatially and spectrally unresolved by the mrs and is a good test of jwst's capabilities. the new mrs spectra reveal a wealth of emission lines not previously detected in this planetary nebula. from these lines, the spectral resolving power (λ/δλ) of the mrs is confirmed to be in the range r = 4000-1500, depending on the mrs spectral sub-band. in addition, the spectra confirm that the carbon-rich dust emission is from complex hydrocarbons and sic grains and that there is little to no time evolution of the sic dust and emission line strengths over a 17-yr epoch. these commissioning data reveal the great potential of the miri mrs for the study of circumstellar and interstellar material. | observations of the planetary nebula smp lmc 058 with the jwst miri medium resolution spectrometer |
a planetary atmosphere is the outer gas layer of a planet. besides its scientific significance among the first and most accessible planetary layers observed from space, it is closely connected with planetary formation and evolution, surface and interior processes, and habitability of planets. current theories of planetary atmospheres were primarily obtained through the studies of eight large planets, pluto and three large moons (io, titan, and triton) in the solar system. outside the solar system, more than four thousand extrasolar planets (exoplanets) and two thousand brown dwarfs have been confirmed in our galaxy, and their population is rapidly growing. the rich information from these exotic bodies offers a database to test, in a statistical sense, the fundamental theories of planetary climates. here we review the current knowledge on atmospheres of exoplanets and brown dwarfs from recent observations and theories. this review highlights important regimes and statistical trends in an ensemble of atmospheres as an initial step towards fully characterizing diverse substellar atmospheres, that illustrates the underlying principles and critical problems. insights are obtained through analysis of the dependence of atmospheric characteristics on basic planetary parameters. dominant processes that influence atmospheric stability, energy transport, temperature, composition and flow pattern are discussed and elaborated with simple scaling laws. we dedicate this review to dr. adam p. showman (1968-2020) in recognition of his fundamental contribution to the understanding of atmospheric dynamics on giant planets, exoplanets and brown dwarfs. | atmospheric regimes and trends on exoplanets and brown dwarfs |
the archaean continental crust comprises two major groups of silicon-rich granitoids: the tonalite-trondhjemite-granodiorite and granite-monzonite-syenite suites, which differ in their sodium-to-potassium ratios. how these felsic granitoids evolved from their mafic precursors remains elusive and the subject of great debate. here, we present silicon isotopic constraints on the formation of representative trondhjemitic and granitic plutons from the kaapvaal craton that range in age from 3.51-2.69 billion years ago. we identified very consistent silicon isotopic signatures, all uniformly 0.1-0.2‰ heavier than rocks of the modern continental crust. this unusual composition is explained by the melting of a mafic source that included significant proportions (15-35 wt%) of silicified basalts, which were common supracrustal rocks before 3 billion years ago. before the melting event that formed the granitoid magmas at depth, portions of the mafic source rocks were enriched in silica by interaction with silica-saturated seawater. the addition of silica depresses the stability of amphibole at similar water activity, allowing trondhjemitic and granitic melt production at lower temperatures from protoliths with contrasting silica contents: 52-57 and ≥60 wt%, respectively. this explains why granitoids were able to form very early in earth history but did not emerge in significant amounts on other rocky planets. | early continental crust generated by reworking of basalts variably silicified by seawater |
near a solid wall, the mean velocity of an incompressible fluid is a nearly universal function of the distance from the wall when appropriately transformed (nondimensionalized). for high-speed compressible flows, due to the wall-normal variations of density and viscosity, it has not been established how to transform a dimensional velocity profile into a universal profile. we propose a transformation that is more accurate and more broadly applicable than existing approaches. this improvement results from deploying different physical arguments for the two critical subdomains of a boundary layer. the transformation can be used to extend incompressible turbulence models to compressible turbulent flows, such as those encountered by vehicles for high-speed transportation and planetary reentry. | velocity transformation for compressible wall-bounded turbulent flows with and without heat transfer |
dust growth is often neglected when building models of protoplanetary disks due to its complexity and computational expense. however, it does play a major role in shaping the evolution of protoplanetary dust and planet formation. in this paper, we present a numerical model coupling 2d hydrodynamic evolution of a protoplanetary disk, including a jupiter-mass planet, and dust coagulation. this is obtained by including multiple dust fluids in a single grid-based hydrodynamic simulation and solving the smoluchowski equation for dust coagulation on top of solving for the hydrodynamic evolution. we find that fragmentation of dust aggregates trapped in a pressure bump outside of the planetary gap leads to an enhancement in the density of small grains. we compare the results obtained from the full-coagulation treatment to the commonly used, fixed-dust-size approach and to previously applied, less computationally intensive methods for including dust coagulation. we find that the full-coagulation results cannot be reproduced using the fixed-size treatment, but some can be mimicked using a relatively simple method for estimating the characteristic dust size in every grid cell. | including dust coagulation in hydrodynamic models of protoplanetary disks: dust evolution in the vicinity of a jupiter-mass planet |
deltas are subaerial landforms that cap underlying deposits with subaqueous extensions that result from a river feeding sediment directly into a standing body of water at a rate that overwhelms any effective dispersal processes derived from the ambient basin. this definition encapsulates both the terrestrial surface expression and the geological focus on the entire sediment mass. environmental studies also focus on the ecology of deltaic wetlands, their drowning history, and related sustainability issues including societal considerations, history, and culture. a mean 76 ± 16% drop in hydraulic energy occurs in all subaerial deltas regardless of size, given the break in gradients separating fluvial and deltaic surfaces, driving an ever-decreasing bed-material transport, shallowing of distributary channels and concomitant overbank flooding. a delta's sediment mass grows from the addition of new river loads but can also include aeolian and marine sediment derived from outside the delta domain, growth of peat and other biomass, and inputs from human action. removal of sediment is via river plumes interacting with marine currents, wave-induced transport, sediment failures and gravity flows, high-tide inundation onto the delta plain, tidal channel widening and deepening, and human action (peat, clay, sand and gravel mining). a delta's trapping efficiency ranges from 0 for small-load rivers that discharge directly into an energetic ocean, to 80% for large deltas, and up to 100% for some semi-enclosed bayhead deltas, including fjords. the global (ensemble) subaerial delta aggradation rate is ∼1.6 mm/y if 70% of the global sediment load exits the river mouth(s), a reminder of how much sediment can be expected to be delivered to the surfaces of global deltas at a time when the 2022 ce sea level rise is ∼4 mm/y. at the planetary scale, deltas are environmentally complex given earth's range in climate, hydrodynamics, tectonic settings, relative sea-level provinces, sediment input, redistribution processes, and human actions. under natural conditions, the subaerial portion of deltas adapt to change by advancing, retreating, switching, aggrading, and/or drowning, whereas many modern deltas are structurally constrained by societal needs. the 89 large and mud-rich coastal marine deltas (i.e. subaerial area > 1000 km2) account for 84.3% of earth's total deltaic area that hosts >89% of all humans occupying deltas, many living within megacities. the 885 medium-size deltas (i.e. subaerial areas 10-1000 km2) account for 15.5% of the global delta area and 10.5% of humans living on deltas, with characteristics that fall between the small and large delta categories. the 1460 small and essentially sandy deltas (1-10 km2), including all fjord deltas, are impacted less from human action (with exceptions) and most are better able to withstand climate change. recognizing the limits of big data in capturing delta complexity, field data remains a necessary gold standard for site investigators. | large deltas, small deltas: toward a more rigorous understanding of coastal marine deltas |
a severe prolonged regional haze episode occurred over the yangtze river delta (yrd) from 2 to 14 december 2013. in this paper, we have discussed the probable cause of haze episode and aerosol characteristics. analysis of visibility and meteorological parameters suggest that the meteorological conditions play a very important role in the accumulation of aerosol particles that cause haze. the height of the planetary boundary layer (pbl) is considered as one of the key factors together with other factors in the haze formation. the principal component analysis (pca) clearly shows accumulation process of air pollutants from vehicular, industrial and anthropogenic sources are major contributors for the haze formation. the aerosol optical properties (aerosol optical depth - aod, ångström exponent - α and ultra violet aerosol index - uvai) are analyzed to study the temporal and spatial variations of aerosol loadings. the results show concentrations of fine mode particles during the haze episode, the dust could have been also entered in the region from the northwestern china. analysis of vertical aerosol profiles indicate that dust aerosols concentrated in the lower part of the haze layers. | analysis of a severe prolonged regional haze episode in the yangtze river delta, china |
diatoms are one of the most ecologically successful classes of photosynthetic marine eukaryotes in the contemporary oceans. over the past 30 million years, they have helped to moderate earth's climate by absorbing carbon dioxide from the atmosphere, sequestering it via the biological carbon pump and ultimately burying organic carbon in the lithosphere. the proportion of planetary primary production by diatoms in the modern oceans is roughly equivalent to that of terrestrial rainforests. in photosynthesis, the efficient conversion of carbon dioxide into organic matter requires a tight control of the atp/nadph ratio which, in other photosynthetic organisms, relies principally on a range of plastid-localized atp generating processes. here we show that diatoms regulate atp/nadph through extensive energetic exchanges between plastids and mitochondria. this interaction comprises the re-routing of reducing power generated in the plastid towards mitochondria and the import of mitochondrial atp into the plastid, and is mandatory for optimized carbon fixation and growth. we propose that the process may have contributed to the ecological success of diatoms in the ocean. | energetic coupling between plastids and mitochondria drives co2 assimilation in diatoms |
executive summarymining has been, and remains, an integral part of human existence from stone age quarries through to the iron and coal that fueled the industrial revolution, to the new materials needed to support the shift to renewable energy. mining and mining products are major contributors to national economies with mining value tripling in the past two decades. as of 2020, the global mining footprint was 57,000 km2 and growing at a faster rate now than any other time in human history. much of this footprint is operational, but in many areas where mining is now complete, the sites represent major environmental liabilities. although site stabilization and managing waste materials remains a challenging part of mine closure in many parts of the world, the environmental liability of these sites means more than being just safe, stable, and nonpolluting, with companies increasingly expected to restore ecosystems that are representative of their pre‑mined (natural) state. the international principles and standards for the ecological restoration and recovery of mine sites (mine site restoration standards, msrs) present the first international framework for the delivery of socially and environmentally responsible ecological restoration after mining, regardless of whether restoration is legally mandated. the msrs are designed to inspire and drive higher and better outcomes in post‑mining landscapes by both guiding and encouraging the highest level of restoration achievable that supports the global need for protecting and restoring nature. this comes at a time of unparalleled global human impacts where climate change, land degradation, and biodiversity loss threaten the very ecological fabric of the planet. mining companies are a major global player in local and regional economies and by demonstrating leadership in protecting, enhancing, and restoring the environments in which they operate, they can maintain, and enhance their social license to operate. the msrs aim to provide a framework for the mining industry, governments, and stakeholders, including indigenous peoples and local communities, to address mining‑specific issues in delivering effective restoration of mine sites. the msrs emphasize that achieving the highest possible ecological outcomes depends upon ingenuity, knowledge investment, and a supportive corporate ethos to build a culture of continuous improvement. this approach will maximize benefits for local communities, the environment, and ultimately the mining industry. for industry, the msrs provide a framework that can be utilized to optimize restoration outcomes that will leave a positive legacy long after mining has ceased. early adoption of the msrs by industry can reduce environmental, financial, and corporate risk in achieving site relinquishment by demonstrating the highest possible commitment to stakeholders, increasing natural capital, responding to climate change and, recovering biodiversity, including threatened and culturally significant species. the agreed‑upon post‑mining land use (pmlu), in some cases, is the same general land use that was present prior to disturbance, which often includes fully functioning intact native ecosystems. in other cases, the pmlu may be different from the pre‑mining condition. regardless, the potential for ecological restoration should not be invoked as a justification for destroying or damaging existing native ecosystems. when native ecosystems are impacted by mining, full recovery informed by reference models should be the target. where this is not achievable a "recovery gap" between the initial native ecosystem and the post‑mining ecosystem is created. in highly man‑altered landscapes, processes and approaches to mine site restoration may require local solutions but should be undertaken within the principles of these standards. when followed, the msrs can help limit the recovery gap, and where possible (e.g., if mining is implemented in an ecosystem that had previously been highly degraded by other activities), close that gap and move toward net ecological gain. the standards are underpinned by eight principles that provide a framework to enable restoration decisions that are evidence‑based, resilient, and acceptable to mining companies, communities, and stakeholders. they are: engage stakeholders throughout the life of mine. draw on many types of knowledge. be informed by reference ecosystems, while considering environmental change. support ecosystem recovery processes. assess against clear goals and objectives, using measurable indicators. seek the highest level of recovery attainable. gain cumulative value when applied at large scales. employ a continuum of restorative activities. the msrs recommend not just best practice, but future practice that harnesses the unique investment and technical capacity of the mining industry and applies it toward the most restorative post‑mining practices possible. these standards align with the united nations decade on ecosystem restoration, the united nations sustainable development goals, the mitigation hierarchy, and international best practice in ecological restoration. they build on the international principles and standards for the practice of ecological restoration with key concepts customized to meet the unique challenges of global mining. the msrs represent a living document that will evolve and develop as technological ability, community and environmental expectations, and understanding of mine site restoration changes over time. | international principles and standards for the ecological restoration and recovery of mine sites |
the exomol project is dedicated to providing molecular line lists for exoplanet and other hot atmospheres. the exomol procedure uses a mixture of ab initio calculations and available laboratory data. the actual line lists are generated using variational nuclear motion calculations. these line lists form the input for opacity models for cool stars and brown dwarfs as well as for radiative transport models involving exoplanets. this paper is a collection of molecular opacities for 52 molecules (130 isotopologues) at two reference temperatures, 300 k and 2000 k, using line lists from the exomol database. so far, exomol line lists have been generated for about 30 key molecular species. other line lists are taken from external sources or from our work predating the exomol project. an overview of the line lists generated by exomol thus far is presented and used to evaluate further molecular data needs. other line lists are also considered. the requirement for completeness within a line list is emphasized and needs for further line lists discussed. | the exomol atlas of molecular opacities |
mars has lost most of its once-abundant water to space, leaving the planet cold and dry. in standard models, molecular hydrogen produced from water in the lower atmosphere diffuses into the upper atmosphere where it is dissociated, producing atomic hydrogen, which is lost. using observations from the neutral gas and ion mass spectrometer on the mars atmosphere and volatile evolution spacecraft, we demonstrate that water is instead transported directly to the upper atmosphere, then dissociated by ions to produce atomic hydrogen. the water abundance in the upper atmosphere varied seasonally, peaking in southern summer, and surged during dust storms, including the 2018 global dust storm. we calculate that this transport of water dominates the present-day loss of atomic hydrogen to space and influenced the evolution of mars’ climate. | hydrogen escape from mars is driven by seasonal and dust storm transport of water |
'oumuamua (i1 2017) was the first macroscopic (l ∼ 100 m) body observed to traverse the inner solar system on an unbound hyperbolic orbit. its light curve displayed strong periodic variation, and it showed no hint of a coma or emission from molecular outgassing. astrometric measurements indicate that 'oumuamua experienced nongravitational acceleration on its outbound trajectory, but energy balance arguments indicate this acceleration is inconsistent with a water ice sublimation-driven jet of the type exhibited by solar system comets. we show that all of 'oumaumua's observed properties can be explained if it contained a significant fraction of molecular hydrogen (h2) ice. h2 sublimation at a rate proportional to the incident solar flux generates a surface-covering jet that reproduces the observed acceleration. mass wasting from sublimation leads to monotonic increase in the body axis ratio, explaining 'oumuamua's shape. back-tracing 'oumuamua's trajectory through the solar system permits calculation of its mass and aspect ratio prior to encountering the sun. we show that h2-rich bodies plausibly form in the coldest dense cores of giant molecular clouds, where number densities are of order n ∼ 105, and temperatures approach the t = 3 k background. post-formation exposure to galactic cosmic rays implies a τ ∼ 100 myr age, explaining the kinematics of 'oumuamua's inbound trajectory. | evidence that 1i/2017 u1 ('oumuamua) was composed of molecular hydrogen ice |
lhs 1140 is a nearby mid-m dwarf known to host a temperate rocky super-earth (lhs 1140 b) on a 24.737-day orbit. based on photometric observations by mearth and spitzer as well as doppler spectroscopy from the high accuracy radial velocity planet searcher, we report the discovery of an additional transiting rocky companion (lhs 1140 c) with a mass of 1.81 ± 0.39 m ⊕ and a radius of 1.282 ± 0.024 r ⊕ on a tighter, 3.77795-day orbit. we also obtain more precise estimates for the mass and radius of lhs 1140 b, which are 6.98 ± 0.89 m ⊕ and 1.727 ± 0.032 r ⊕. the mean densities of planets b and c are 7.5 ± 1.0 g cm-3 and 4.7 ± 1.1 g cm-3, respectively, both consistent with the earth’s ratio of iron to magnesium silicate. the orbital eccentricities of lhs 1140 b and c are consistent with circular orbits and constrained to be below 0.06 and 0.31, respectively, with 90% confidence. because the orbits of the two planets are coplanar and because we know from previous analyses of kepler data that compact systems of small planets orbiting m dwarfs are commonplace, a search for more transiting planets in the lhs 1140 system could be fruitful. lhs 1140 c is one of the few known nearby terrestrial planets whose atmosphere could be studied with the upcoming james webb space telescope. | a second terrestrial planet orbiting the nearby m dwarf lhs 1140 |
in the search for life on earth-like planets around other stars, the first (and likely only) information will come from the spectroscopic characterization of the planet's atmosphere. of the countless number of chemical species terrestrial life produces, only a few have the distinct spectral features and the necessary atmospheric abundance to be detectable. the easiest of these species to observe in earth's atmosphere is o2 (and its photochemical byproduct, o3). however, o2 can also be produced abiotically by photolysis of co2, followed by recombination of o atoms with each other. co is produced in stoichiometric proportions. whether o2 and co can accumulate to appreciable concentrations depends on the ratio of far-ultraviolet (fuv) to near-ultraviolet (nuv) radiation coming from the planet's parent star and on what happens to these gases when they dissolve in a planet's oceans. using a one-dimensional photochemical model, we demonstrate that o2 derived from co2 photolysis should not accumulate to measurable concentrations on planets around f- and g-type stars. k-star, and especially m-star planets, however, may build up o2 because of the low nuv flux from their parent stars, in agreement with some previous studies. on such planets, a “false positive” for life is possible if recombination of dissolved co and o2 in the oceans is slow and if other o2 sinks (e.g., reduced volcanic gases or dissolved ferrous iron) are small. o3, on the other hand, could be detectable at uv wavelengths (λ < 300 nm) for a much broader range of boundary conditions and stellar types. | abiotic o2 levels on planets around f, g, k, and m stars: possible false positives for life? |
context. the planetary system discovered around the young a-type hr 8799 provides a unique laboratory to: a) test planet formation theories; b) probe the diversity of system architectures at these separations, and c) perform comparative (exo)planetology.aims: we present and exploit new near-infrared images and integral-field spectra of the four gas giants surrounding hr 8799 obtained with sphere, the new planet finder instrument at the very large telescope, during the commissioning and science verification phase of the instrument (july-december 2014). with these new data, we contribute to completing the spectral energy distribution (sed) of these bodies in the 1.0-2.5 μm range. we also provide new astrometric data, in particular for planet e, to further constrain the orbits.methods: we used the infrared dual-band imager and spectrograph (irdis) subsystem to obtain pupil-stabilized, dual-band h2h3 (1.593 μm, 1.667 μm), k1k2 (2.110 μm, 2.251 μm), and broadband j (1.245 μm) images of the four planets. irdis was operated in parallel with the integral field spectrograph (ifs) of sphere to collect low-resolution (r ~ 30), near-infrared (0.94-1.64 μm) spectra of the two innermost planets hr 8799 d and e. the data were reduced with dedicated algorithms, such as the karhunen-loève image projection (klip), to reveal the planets. we used the so-called negative planets injection technique to extract their photometry, spectra, and measure their positions. we illustrate the astrometric performance of sphere through sample orbital fits compatible with sphere and literature data.results: we demonstrated the ability of sphere to detect and characterize planets in this kind of systems, providing spectra and photometry of its components. the spectra improve upon the signal-to-noise ratio of previously obtained data and increase the spectral coverage down to the y band. in addition, we provide the first detection of planet e in the j band. astrometric positions for planets hr 8799 bcde are reported for the epochs of july, august, and december 2014. we measured the photometric values in j, h2h3, k1k2 bands for the four planets with a mean accuracy of 0.13 mag. we found upper limit constraints on the mass of a possible planet f of 3-7 mjup . our new measurements are more consistent with the two inner planets d and e being in a 2d:1e or 3d:2e resonance. the spectra of hr 8799 d and e are well matched by those of l6-8 field dwarfs. however, the seds of these objects are redder than field l dwarfs longward of 1.6 μm. based on observations collected at the european southern observatory (eso), chile, during the commissioning of the sphere instrument and during the science verification (program number 60.a-9352(a)).spectra of planets are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/587/a57 | first light of the vlt planet finder sphere. iii. new spectrophotometry and astrometry of the hr 8799 exoplanetary system |
we infer dynamical masses in eight multiplanet systems using transit times measured from kepler's complete data set, including short-cadence data where available. of the 18 dynamical masses that we infer, 10 pass multiple tests for robustness. these are in systems kepler-26 (koi-250), kepler-29 (koi-738), kepler-60 (koi-2086), kepler-105 (koi-115), and kepler-307 (koi-1576). kepler-105 c has a radius of 1.3 r⊕ and a density consistent with an earth-like composition. strong transit timing variation (ttv) signals were detected from additional planets, but their inferred masses were sensitive to outliers or consistent solutions could not be found with independently measured transit times, including planets orbiting kepler-49 (koi-248), kepler-57 (koi-1270), kepler-105 (koi-115), and kepler-177 (koi-523). nonetheless, strong upper limits on the mass of kepler-177 c imply an extremely low density of ∼0.1 g cm-3. in most cases, individual orbital eccentricities were poorly constrained owing to degeneracies in ttv inversion. for five planet pairs in our sample, strong secular interactions imply a moderate to high likelihood of apsidal alignment over a wide range of possible eccentricities. we also find solutions for the three planets known to orbit kepler-60 in a laplace-like resonance chain. however, nonlibrating solutions also match the transit timing data. for six systems, we calculate more precise stellar parameters than previously known, enabling useful constraints on planetary densities where we have secure mass measurements. placing these exoplanets on the mass-radius diagram, we find that a wide range of densities is observed among sub-neptune-mass planets and that the range in observed densities is anticorrelated with incident flux. | secure mass measurements from transit timing: 10 kepler exoplanets between 3 and 8 m⊕ with diverse densities and incident fluxes |
standard accretion disk models suggest that the snow line in the solar nebula migrated interior to the earth's orbit in a late stage of nebula evolution. in this late stage, a significant amount of ice could have been delivered to 1 au from outer regions in the form of mm to dm-sized pebbles. this raises the question why the present earth is so depleted of water (with the ocean mass being as small as 0.023% of the earth mass). here we quantify the amount of icy pebbles accreted by terrestrial embryos after the migration of the snow line assuming that no mechanism halts the pebble flow in outer disk regions. we use a simplified version of the coagulation equation to calculate the formation and radial inward drift of icy pebbles in a protoplanetary disk. the pebble accretion cross section of an embryo is calculated using analytic expressions presented by recent studies. we find that the final mass and water content of terrestrial embryos strongly depends on the radial extent of the gas disk, the strength of disk turbulence, and the time at which the snow lines arrives at 1 au. the disk's radial extent sets the lifetime of the pebble flow, while turbulence determines the density of pebbles at the midplane where the embryos reside. we find that the final water content of the embryos falls below 0.023 wt% only if the disk is compact (<100 au), turbulence is strong at 1 au, and the snow line arrives at 1 au later than 2-4 myr after disk formation. if the solar nebula extended to 300 au, initially rocky embryos would have evolved into icy planets of 1-10 earth masses unless the snow-line migration was slow. if the proto-earth contained water of ~1 wt% as might be suggested by the density deficit of the earth's outer core, the formation of the proto-earth was possible with weaker turbulence and with earlier (>0.5-2 myr) snow-line migration. | on the water delivery to terrestrial embryos by ice pebble accretion |
context. near- to mid-infrared observations of molecular emission from protoplanetary disks show that the inner regions are rich in small organic volatiles (e.g., c2h2 and hcn). trends in the data suggest that disks around cooler stars (teff ≈ 3000 k) are potentially (i) more carbon-rich; and (ii) more molecule-rich than their hotter counterparts (teff ≳ 4000 k).aims: we explore the chemical composition of the planet-forming region (<10 au) of protoplanetary disks around stars over a range of spectral types (from m dwarf to herbig ae) and compare with the observed trends.methods: self-consistent models of the physical structure of a protoplanetary disk around stars of different spectral types are coupled with a comprehensive gas-grain chemical network to map the molecular abundances in the planet-forming zone. the effects of (i) n2 self shielding; (ii) x-ray-induced chemistry; and (iii) initial abundances, are investigated. the chemical composition in the "observable" atmosphere is compared with that in the disk midplane where the bulk of the planet-building reservoir resides.results: m dwarf disk atmospheres are relatively more molecule rich than those for t tauri or herbig ae disks. the weak far-uv flux helps retain this complexity which is enhanced by x-ray-induced ion-molecule chemistry. n2 self shielding has only a small effect in the disk molecular layer and does not explain the higher c2h2/hcn ratios observed towards cooler stars. the models underproduce the oh/h2o column density ratios constrained in herbig ae disks, despite reproducing (within an order of magnitude) the absolute value for oh: the inclusion of self shielding for h2o photodissociation only increases this discrepancy. one possible explanation is the adopted disk structure. alternatively, the "hot" h2o (t ≳ 300 k) chemistry may be more complex than assumed. the results for the atmosphere are independent of the assumed initial abundances; however, the composition of the disk midplane is sensitive to the initial main elemental reservoirs. the models show that the gas in the inner disk is generally more carbon rich than the midplane ices. this effect is most significant for disks around cooler stars. furthermore, the atmospheric c/o ratio appears larger than it actually is when calculated using observable tracers only. this is because gas-phase o2 is predicted to be a significant reservoir of atmospheric oxygen.conclusions: the models suggest that the gas in the inner regions of disks around cooler stars is more carbon rich; however, calculations of the molecular emission are necessary to definitively confirm whether the chemical trends reproduce the observed trends. appendix a is available in electronic form at http://www.aanda.org | the molecular composition of the planet-forming regions of protoplanetary disks across the luminosity regime |
rings and radial gaps are ubiquitous in protoplanetary disks, yet their possible connection to planet formation is currently subject to intense debates. in principle, giant planet formation leads to wide gaps that separate the gas and dust mass reservoir in the outer disk, while lower mass planets lead to shallow gaps that are manifested mainly on the dust component. we used the atacama large millimeter/submillimeter array (alma) to observe the star hd 169142, host to a prominent disk with deep, wide gaps that sever the disk into inner and outer regions. the new alma high-resolution images allow for the outer ring to be resolved as three narrow rings. the hd 169142 disk thus hosts both the wide gap trait of transition disks and a narrow-ring system similar to those observed in the tw hya and hl tau systems. the mass reservoir beyond a deep gap can thus host ring systems. the observed rings are narrow in radial extent (width/radius of 1.5/57.3, 1.8/64.2, and 3.4/76.0 in au) and have asymmetric mutual separations: the first and middle ring are separated by 7 au while the middle and outermost ring are distanced by ∼12 au. using hydrodynamical modeling we found that a simple explanation, involving a single migrating low-mass planet (10 m ⊕), entirely accounts for such an apparently complex phenomenon. inward migration of the planet naturally explains the ring’s asymmetric mutual separation. the isolation of hd 169142's outer rings thus allows a proof of concept to interpret the detailed architecture of the outer region of protoplanetary disks with low-mass planet formation of mini-neptune’s size, i.e., as in the protosolar nebula. | dust unveils the formation of a mini-neptune planet in a protoplanetary ring |
context. large surveys with new-generation high-contrast imaging instruments are needed to derive the frequency and properties of exoplanet populations with separations from ~5 to 300 au. a careful assessment of the stellar properties is crucial for a proper understanding of when, where, and how frequently planets form, and how they evolve. the sensitivity of detection limits to stellar age makes this a key parameter for direct imaging surveys.aims: we describe the sphere infrared survey for exoplanets (shine), the largest direct imaging planet-search campaign initiated at the vlt in 2015 in the context of the sphere guaranteed time observations of the sphere consortium. in this first paper we present the selection and the properties of the complete sample of stars surveyed with shine, focusing on the targets observed during the first phase of the survey (from february 2015 to february 2017). this early sample composed of 150 stars is used to perform a preliminary statistical analysis of the shine data, deferred to two companion papers presenting the survey performance, main discoveries, and the preliminary statistical constraints set by shine.methods: based on a large database collecting the stellar properties of all young nearby stars in the solar vicinity (including kinematics, membership to moving groups, isochrones, lithium abundance, rotation, and activity), we selected the original sample of 800 stars that were ranked in order of priority according to their sensitivity for planet detection in direct imaging with sphere. the properties of the stars that are part of the early statistical sample wererevisited, including for instance measurements from the gaia data release 2. rotation periods were derived for the vast majority of the late-type objects exploiting tess light curves and dedicated photometric observations.results: the properties of individual targets and of the sample as a whole are presented. tables 5-11 are only available at the cds via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/651/a70 | the sphere infrared survey for exoplanets (shine). i. sample definition and target characterization |
we present the first detection of (z)-1,2-ethenediol, (choh)2, the enol form of glycolaldehyde, in the interstellar medium toward the g+0.693-0.027 molecular cloud located in the galactic center. we have derived a column density of (1.8 ± 0.1) × 1013 cm-2, which translates into a molecular abundance with respect to molecular hydrogen of 1.3 × 10-10. the abundance ratio between glycolaldehyde and (z)-1,2-ethenediol is ~5.2. we discuss several viable formation routes through chemical reactions from precursors such as hco, h2co, choh, or ch2choh. we also propose that this species might be an important precursor in the formation of glyceraldehyde (hoch2chohcho) in the interstellar medium through combination with the hydroxymethylene (choh) radical. | precursors of the rna world in space: detection of (z)-1,2-ethenediol in the interstellar medium, a key intermediate in sugar formation |
this multi-petawatt physics prioritization (mp3) workshop report captures the outcomes from a community-initiated workshop held april 20-22, 2022 at sorbonne university in paris, france. the mp3 workshop aimed at developing science questions to guide research and future experiments in four areas identified by corresponding mp3 working groups: high-field physics and quantum electrodynamics (hfp/qed), laboratory astrophysics and planetary physics (lapp), laser-driven nuclear physics (ldnp), and particle acceleration and advanced light sources (paals). | multi-petawatt physics prioritization (mp3) workshop report |
the nasa double asteroid redirection test (dart) spacecraft successfully crashed on dimorphos, the secondary component of the binary (65803) didymos system. following the impact, a large dust cloud was released, and a long-lasting dust tail developed. we have extensively monitored the dust tail from the ground and the hubble space telescope. we provide a characterization of the ejecta dust properties, i.e., particle size distribution and ejection speeds, ejection geometric parameters, and mass, by combining both observational data sets and using monte carlo models of the observed dust tail. the size distribution function that best fits the imaging data is a broken power law having a power index of -2.5 for particles of r ≤ 3 mm and -3.7 for larger particles. the particles range in size from 1 μm up to 5 cm. the ejecta is characterized by two components, depending on velocity and ejection direction. the northern component of the double tail, observed since 2022 october 8, might be associated with a secondary ejection event from impacting debris on didymos, although is also possible that this feature results from the binary system dynamics alone. the lower limit to the total dust mass ejected is estimated at ~6 × 106 kg, half of this mass being ejected to interplanetary space. | characterization of the ejecta from the nasa/dart impact on dimorphos: observations and monte carlo models |
context. the sphere "planet finder" is an extreme adaptive optics (ao) instrument for high resolution and high contrast observations at the very large telescope (vlt). we describe the zurich imaging polarimeter (zimpol), the visual focal plane subsystem of sphere, which pushes the limits of current ao systems to shorter wavelengths, higher spatial resolution, and much improved polarimetric performance.aims: we present a detailed characterization of sphere/zimpol which should be useful for an optimal planning of observations and for improving the data reduction and calibration. we aim to provide new benchmarks for the performance of high contrast instruments, in particular for polarimetric differential imaging.methods: we have analyzed sphere/zimpol point spread functions (psfs) and measure the normalized peak surface brightness, the encircled energy, and the full width half maximum (fwhm) for different wavelengths, atmospheric conditions, star brightness, and instrument modes. coronagraphic images are described and the peak flux attenuation and the off-axis flux transmission are determined. simultaneous images of the coronagraphic focal plane and the pupil plane are analyzed and the suppression of the diffraction rings by the pupil stop is investigated. we compared the performance at small separation for different coronagraphs with tests for the binary α hyi with a separation of 92 mas and a contrast of δm ≈ 6m. for the polarimetric mode we made the instrument calibrations using zero polarization and high polarization standard stars and here we give a recipe for the absolute calibration of polarimetric data. the data show small (< 1 mas) but disturbing differential polarimetric beam shifts, which can be explained as goos-hähnchen shifts from the inclined mirrors, and we discuss how to correct this effect. the polarimetric sensitivity is investigated with non-coronagraphic and deep, coronagraphic observations of the dust scattering around the symbiotic mira variable r aqr.results: sphere/zimpol reaches routinely an angular resolution (fwhm) of 22-28 mas, and a normalized peak surface brightness of sb0 - mstar ≈ -6.5m arcsec-2 for the v-, r- and i-band. the ao performance is worse for mediocre ≳1.0″ seeing conditions, faint stars mr ≳ 9m, or in the presence of the "low wind" effect (telescope seeing). the coronagraphs are effective in attenuating the psf peak by factors of > 100, and the suppression of the diffracted light improves the contrast performance by a factor of approximately two in the separation range 0.06″-0.20″. the polarimetric sensitivity is δp < 0.01% and the polarization zero point can be calibrated to better than δp ≈ 0.1%. the contrast limits for differential polarimetric imaging for the 400 s i-band data of r aqr at a separation of ρ = 0.86″ are for the surface brightness contrast sbpol( ρ)-mstar ≈ 8m arcsec-2 and for the point source contrast mpol( ρ)-mstar ≈ 15m and much lower limits are achievable with deeper observations.conclusions: sphere/zimpol achieves imaging performances in the visual range with unprecedented characteristics, in particular very high spatial resolution and very high polarimetric contrast. this instrument opens up many new research opportunities for the detailed investigation of circumstellar dust, in scattered and therefore polarized light, for the investigation of faint companions, and for the mapping of circumstellar hα emission. based on observations collected at la silla and paranal observatory, eso (chile), program id: 60.a-9249 and 60.a-9255. | sphere/zimpol high resolution polarimetric imager. i. system overview, psf parameters, coronagraphy, and polarimetry |
the planets of the solar system are neatly divided between those with atmospheres and those without when arranged by insolation (i) and escape velocity ({v}{esc}). the dividing line goes at i\propto {v}{esc}4. exoplanets with reported masses and radii are shown to crowd against the extrapolation of the solar system trend, making a metaphorical cosmic shoreline that unites all the planets. the i\propto {v}{esc}4 relation may implicate thermal escape. we therefore address the general behavior of hydrodynamic thermal escape models ranging from pluto to highly irradiated extrasolar giant planets (egps). energy-limited escape is harder to test because copious xuv radiation is mostly a feature of young stars, and hence requires extrapolating to historic xuv fluences ({i}{xuv}) using proxies and power laws. an energy-limited shoreline should scale as {i}{xuv}\propto {v}{esc}3\sqrt{ρ }, which differs distinctly from the apparent {i}{xuv}\propto {v}{esc}4 relation. energy-limited escape does provide good quantitative agreement to the highly irradiated egps. diffusion-limited escape implies that no planet can lose more than 1% of its mass as h2. impact erosion, to the extent that impact velocities {v}{imp} can be estimated for exoplanets, fits a {v}{imp}≈ 4{--}5 {v}{esc} shoreline. the proportionality constant is consistent with what the collision of comet shoemaker-levy 9 showed us we should expect of modest impacts in deep atmospheres. with respect to the shoreline, proxima centauri b is on the metaphorical beach. known hazards include its rapid energetic accretion, high impact velocities, its early life on the wrong side of the runaway greenhouse, and proxima centauri’s xuv radiation. in its favor is a vast phase space of unknown unknowns. | the cosmic shoreline: the evidence that escape determines which planets have atmospheres, and what this may mean for proxima centauri b |
the emergence and expansion of complex eukaryotic life on earth is linked at a basic level to the secular evolution of surface oxygen levels. however, the role that planetary redox evolution has played in controlling the timing of metazoan (animal) emergence and diversification, if any, has been intensely debated. discussion has gravitated toward threshold levels of environmental free oxygen (o2) necessary for early evolving animals to survive under controlled conditions. however, defining such thresholds in practice is not straightforward, and environmental o2 levels can potentially constrain animal life in ways distinct from threshold o2 tolerance. herein, we quantitatively explore one aspect of the evolutionary coupling between animal life and earth’s oxygen cycle—the influence of spatial and temporal variability in surface ocean o2 levels on the ecology of early metazoan organisms. through the application of a series of quantitative biogeochemical models, we find that large spatiotemporal variations in surface ocean o2 levels and pervasive benthic anoxia are expected in a world with much lower atmospheric po2 than at present, resulting in severe ecological constraints and a challenging evolutionary landscape for early metazoan life. we argue that these effects, when considered in the light of synergistic interactions with other environmental parameters and variable o2 demand throughout an organism’s life history, would have resulted in long-term evolutionary and ecological inhibition of animal life on earth for much of middle proterozoic time (∼1.8-0.8 billion years ago). | earth's oxygen cycle and the evolution of animal life |
recently, many superflares on solar-type stars have been discovered as white-light flares (wlfs). the statistical study found a correlation between their energies (e) and durations (τ): τ \propto {e}0.39, similar to those of solar hard/soft x-ray flares, τ \propto {e}0.2{--0.33}. this indicates a universal mechanism of energy release on solar and stellar flares, i.e., magnetic reconnection. we here carried out statistical research on 50 solar wlfs observed with solar dynamics observatory/hmi and examined the correlation between the energies and durations. as a result, the e-τ relation on solar wlfs (τ \propto {e}0.38) is quite similar to that on stellar superflares (τ \propto {e}0.39). however, the durations of stellar superflares are one order of magnitude shorter than those expected from solar wlfs. we present the following two interpretations for the discrepancy: (1) in solar flares, the cooling timescale of wlfs may be longer than the reconnection one, and the decay time of solar wlfs can be elongated by the cooling effect; (2) the distribution can be understood by applying a scaling law (τ \propto {e}1/3{b}-5/3) derived from the magnetic reconnection theory. in the latter case, the observed superflares are expected to have 2-4 times stronger magnetic field strength than solar flares. | statistical studies of solar white-light flares and comparisons with superflares on solar-type stars |
we report the development of a four-color simultaneous camera for the 1.52-m telescopio carlos sánchez in the teide observatory, canaries, spain. the instrument, named muscat2, has a capability of four-color simultaneous imaging in g (400 to 550 nm), r (550 to 700 nm), i (700 to 820 nm), and zs (820 to 920 nm) bands. muscat2 equips four 1024 × 1024 pixel ccds, having a field of view of 7.4 × 7.4 arc min2 with a pixel scale of 0.44 arc sec per pixel. the principal purpose of muscat2 is to perform high-precision multicolor exoplanet transit photometry. we demonstrate photometric precisions of 0.057%, 0.050%, 0.060%, and 0.076% as root-mean-square residuals of 60 s binning in g, r, i, and zs bands, respectively, for a g0 v star wasp-12 (v = 11.57 ± 0.16). muscat2 has started science operations since january 2018, with over 250 telescope nights per year. muscat2 is expected to become a reference tool for exoplanet transit observations and substantially contributes to the follow-up of the transiting exoplanet survey satellite and planetary transits and oscillations of stars space missions. | muscat2: four-color simultaneous camera for the 1.52-m telescopio carlos sánchez |
we present deep hubble space telescope images taken to examine the ejecta from the dart spacecraft impact into asteroid dimorphos. the images reveal an extensive population of comoving boulders, the largest of which is ~7 m in diameter (geometric albedo 0.15 assumed). measurements of 37 boulders show a mean sky-plane velocity dispersion of 0.30 ± 0.03 m s-1, only slightly larger than the 0.24 m s-1 gravitational escape velocity from the didymos-dimorphos binary system. the total boulder mass, mb~ 5 × 106 kg (density 2200 kg m-3 assumed), corresponds to about 0.1% of the mass of dimorphos, and the boulders collectively carry about 3 × 10-5 of the kinetic energy delivered by the dart spacecraft impact. the sky-plane distribution of the boulders is asymmetric, consistent with impact into an inhomogeneous, likely rubble-pile, body. surface boulder counts on didymos show that the observed boulder swarm could be ejected from as little as 2% of the surface of dimorphos (for example, a circular crater at the impact point about 50 m in diameter). the large, slow-moving boulders are potential targets to be investigated in situ by the upcoming esa hera mission. | the dimorphos boulder swarm |
on 4 july 2019, the ridgecrest earthquake sequence began with a series of foreshocks including an mw 6.4 event near searles valley, california. this was then followed 34 hr later by an mw 7.1 mainshock located just 15 km to the north, with the earthquake sequence resulting in a complex array of intersecting faults. this earthquake sequence poses several interesting questions including, did the stress changes induced by the mw 6.4 foreshock trigger the mw 7.1 mainshock and what possible mechanism(s) could explain the occurrence of widespread secondary faulting surrounding both surface ruptures? however, most of the geodetic data (such as interferometric synthetic aperture radar, light detection and ranging, and optical satellite imagery) were acquired after both events had occurred making it difficult to discern which surface fractures happened when and their possible triggering mechanism. here, we provide a dataset composed of high-resolution optical imagery, pixel-value difference maps, .kmz fracturing mapping, and horizontal deformation maps derived from subpixel image correlation, which can uniquely separate the surface fracturing and deformation between the foreshock and mainshock events that can help answer these questions. separate imaging of the events is made possible by the daily acquisition of optical imagery by the planet labs cubesat constellation, which acquired data between the two earthquakes, in the morning of 4 and 5 july, at 11.13 a.m. and 05.12 p.m. pst, respectively, with the images acquired just 40 min after the foreshock and 56 min before the mainshock, respectively. analysis from this optical imagery reveals the location of surface faulting that allows us to map their spatial extent and determine their timing. these data which we provide here can help guide and validate field survey observations to help understand which faults ruptured when, and constrain slip inversion models for more accurate estimates of stress changes induced by the foreshock imposed on the surrounding faults. | using daily observations from planet labs satellite imagery to separate the surface deformation between the 4 july mw 6.4 foreshock and 5 july mw 7.1 mainshock during the 2019 ridgecrest earthquake sequence |
the magnetosheath flow may take the form of large amplitude, yet spatially localized, transient increases in dynamic pressure, known as "magnetosheath jets" or "plasmoids" among other denominations. here, we describe the present state of knowledge with respect to such jets, which are a very common phenomenon downstream of the quasi-parallel bow shock. we discuss their properties as determined by satellite observations (based on both case and statistical studies), their occurrence, their relation to solar wind and foreshock conditions, and their interaction with and impact on the magnetosphere. as carriers of plasma and corresponding momentum, energy, and magnetic flux, jets bear some similarities to bursty bulk flows, which they are compared to. based on our knowledge of jets in the near earth environment, we discuss the expectations for jets occurring in other planetary and astrophysical environments. we conclude with an outlook, in which a number of open questions are posed and future challenges in jet research are discussed. | jets downstream of collisionless shocks |
celestial bodies with a mass of m≈ 10 {m}{jup} have been found orbiting nearby stars. it is unknown whether these objects formed like gas-giant planets through core accretion or like stars through gravitational instability. i show that objects with m≲ 4 {m}{jup} orbit metal-rich solar-type dwarf stars, a property associated with core accretion. objects with m≳ 10 {m}{jup} do not share this property. this transition is coincident with a minimum in the occurrence rate of such objects, suggesting that the maximum mass of a celestial body formed through core accretion like a planet is less than 10 {m}{jup}. consequently, objects with m≳ 10 {m}{jup} orbiting solar-type dwarf stars likely formed through gravitational instability and should not be thought of as planets. theoretical models of giant planet formation in scaled minimum-mass solar nebula shakura-sunyaev disks with standard parameters tuned to produce giant planets predict a maximum mass nearly an order of magnitude larger. to prevent newly formed giant planets from growing larger than 10 {m}{jup}, protoplanetary disks must therefore be significantly less viscous or of lower mass than typically assumed during the runaway gas accretion stage of giant planet formation. either effect would act to slow the type i/ii migration of planetary embryos/giant planets and promote their survival. these inferences are insensitive to the host star mass, planet formation location, or characteristic disk dissipation time. | evidence of an upper bound on the masses of planets and its implications for giant planet formation |
camera traps have become a ubiquitous tool in ecology and conservation. they are routinely deployed in wildlife survey and monitoring work, and are being advocated as a tool for planetary-scale biodiversity monitoring. the camera trap's widespread adoption is predicated on the assumption of its effectiveness, but the evidence base for this is lacking. using 104 past studies, we recorded the qualitative overall recommendations made by study authors (for or against camera traps, or ambiguous), together with quantitative data on the effectiveness of camera traps (e.g. number of species detected or detection probabilities) relative to 22 other methods. most studies recommended the use of camera traps overall and they were 39% more effective based on the quantitative data. they were significantly more effective compared with live traps (88%) and were otherwise comparable in effectiveness to other methods. camera traps were significantly more effective than other methods at detecting a large number of species (31% more) and for generating detections of species (91% more). this makes camera traps particularly suitable for broad-spectrum biodiversity surveys. film camera traps were found to be far less effective than digital models, which has led to an increase in camera trap effectiveness over time. there was also evidence from the authors that the use of attractants with camera traps reduced their effectiveness (counter to their intended effect), while the quantitative data indicated that camera traps were more effective in closed than open habitats. camera traps are a highly effective wildlife survey tool and their performance will only improve with future technological advances. the images they produce also have a range of other benefits, for example as digital voucher specimens and as visual aids for outreach. the evidence-base supports the increasing use of camera traps and underlines their suitability for meeting the challenges of global-scale biodiversity monitoring. | snap happy: camera traps are an effective sampling tool when compared with alternative methods |
understanding the dynamics and kinematics of outflowing atmospheres of hot and warm exoplanets is crucial to understanding the origins and evolutionary history of the exoplanets near the evaporation desert. recently, ground-based measurements of the meta-stable helium atom's resonant absorption at 10830 å has become a powerful probe of the base environment which is driving the outflow of exoplanet atmospheres. we report evidence for the he i 10830 å in absorption (equivalent width ∼0.012 ± 0.002 å) in the exosphere of a warm neptune orbiting the m-dwarf gj 3470, during three transits using the habitable zone planet finder near-infrared spectrograph. this marks the first reported evidence for he i 10830 å atmospheric absorption for a planet orbiting an m-dwarf. our detected absorption is broad and its blueshifted wing extends to -36 km s-1, the largest reported in the literature to date. we modeled the state of helium atoms in the exosphere of gj3470b based on assumptions on the uv and x-ray flux of gj 3470, and found our measurement of flux-weighted column density of meta-stable state helium $({n}_{\mathrm{he}{}_{3}^{2}{\rm{s}}}=2.4\times {10}^{10}\,{\mathrm{cm}}^{-2})$ , derived from our transit observations, to be consistent with the model, within its uncertainties. the methodology developed here will be useful to study and constrain the atmospheric outflow models of other exoplanets like gj 3470b, which are near the edge of the evaporation desert. | evidence for he i 10830 å absorption during the transit of a warm neptune around the m-dwarf gj 3470 with the habitable-zone planet finder |
ariel has been selected as esa’s m4 mission for launch in 2028 and is designed for the characterization of a large and diverse population of exoplanetary atmospheres to provide insights into planetary formation and evolution within our galaxy. here we present a study of ariel’s capability to observe currently known exoplanets and predicted transiting exoplanet survey satellite (tess) discoveries. we use the ariel radiometric model (arielrad) to simulate the instrument performance and find that ∼2000 of these planets have atmospheric signals which could be characterized by ariel. this list of potential planets contains a diverse range of planetary and stellar parameters. from these we select an example mission reference sample (mrs), comprised of 1000 diverse planets to be completed within the primary mission life, which is consistent with previous studies. we also explore the mission capability to perform an in-depth survey into the atmospheres of smaller planets, which may be enriched or secondary. earth-sized planets and super-earths with atmospheres heavier than h/he will be more challenging to observe spectroscopically. however, by studying the time required to observe ∼110 earth-sized/super-earths, we find that ariel could have substantial capability for providing in-depth observations of smaller planets. trade-offs between the number and type of planets observed will form a key part of the selection process and this list of planets will continually evolve with new exoplanet discoveries replacing predicted detections. the ariel target list will be constantly updated and the mrs re-selected to ensure maximum diversity in the population of planets studied during the primary mission life. | an updated study of potential targets for ariel |
using the keck planet imager and characterizer, we obtained high-resolution (r ~ 35,000) k-band spectra of the four planets orbiting hr 8799. we clearly detected h2o and co in the atmospheres of hr 8799 c, d, and e, and tentatively detected a combination of co and h2o in b. these are the most challenging directly imaged exoplanets that have been observed at high spectral resolution to date when considering both their angular separations and flux ratios. we developed a forward-modeling framework that allows us to jointly fit the spectra of the planets and the diffracted starlight simultaneously in a likelihood-based approach and obtained posterior probabilities on their effective temperatures, surface gravities, radial velocities, and spins. we measured $v\sin (i)$ values of ${10.1}_{-2.7}^{+2.8}\,\mathrm{km}\,{{\rm{s}}}^{-1}$ for hr 8799 d and ${15.0}_{-2.6}^{+2.3}\,\mathrm{km}\,{{\rm{s}}}^{-1}$ for hr 8799 e, and placed an upper limit of <14 km s-1 of hr 8799 c. under two different assumptions of their obliquities, we found tentative evidence that rotation velocity is anticorrelated with companion mass, which could indicate that magnetic braking with a circumplanetary disk at early times is less efficient at spinning down lower-mass planets. | detection and bulk properties of the hr 8799 planets with high-resolution spectroscopy |
we report the discovery and characterisation of a super-earth and a sub-neptune transiting the bright (k = 8.8), quiet, and nearby (37 pc) m3v dwarf toi-1266. we validate the planetary nature of toi-1266 b and c using four sectors of tess photometry and data from the newly-commissioned 1-m saint-ex telescope located in san pedro mártir (méxico). we also include additional ground-based follow-up photometry as well as high-resolution spectroscopy and high-angular imaging observations. the inner, larger planet has a radius of r = 2.37-0.12+0.16 r⊕ and an orbital period of 10.9 days. the outer, smaller planet has a radius of r = 1.56-0.13+0.15 r⊕ on an 18.8-day orbit. the data are found to be consistent with circular, co-planar and stable orbits that are weakly influenced by the 2:1 mean motion resonance. our ttv analysis of the combined dataset enables model-independent constraints on the masses and eccentricities of the planets. we find planetary masses of mp = 13.5-9.0+11.0 m⊕ (<36.8 m⊕ at 2-σ) for toi-1266 b and 2.2-1.5+2.0 m⊕ (<5.7 m⊕ at 2-σ) for toi-1266 c. we find small but non-zero orbital eccentricities of 0.09-0.05+0.06 (<0.21 at 2-σ) for toi-1266 b and 0.04 ± 0.03 (< 0.10 at 2-σ) for toi-1266 c. the equilibrium temperatures of both planets are of 413 ± 20 and 344 ± 16 k, respectively, assuming a null bond albedo and uniform heat redistribution from the day-side to the night-side hemisphere. the host brightness and negligible activity combined with the planetary system architecture and favourable planet-to-star radii ratios makes toi-1266 an exquisite system for a detailed characterisation. | a super-earth and a sub-neptune orbiting the bright, quiet m3 dwarf toi-1266 |
comets are icy objects that orbitally evolve from the trans-neptunian region into the inner solar system, where they are heated by solar radiation and become active due to the sublimation of water ice. here we perform simulations in which cometary reservoirs are formed in the early solar system and evolved over 4.5 gyr. the gravitational effects of planet 9 (p9) are included in some simulations. different models are considered for comets to be active, including a simple assumption that comets remain active for {n}{{p}}(q) perihelion passages with perihelion distance q< 2.5 {au}. the orbital distribution and number of active comets produced in our model is compared to observations. the orbital distribution of ecliptic comets (ecs) is well reproduced in models with {n}{{p}}(2.5)≃ 500 and without p9. with p9, the inclination distribution of model ecs is wider than the observed one. we find that the known halley-type comets (htcs) have a nearly isotropic inclination distribution. the htcs appear to be an extension of the population of returning oort-cloud comets (occs) to shorter orbital periods. the inclination distribution of model htcs becomes broader with increasing {n}{{p}}, but the existing data are not good enough to constrain {n}{{p}} from orbital fits. {n}{{p}}(2.5)> 1000 is required to obtain a steady-state population of large active htcs that is consistent with observations. to fit the ratio of the returning-to-new occs, by contrast, our model implies that {n}{{p}}(2.5)≲ 10, possibly because the detected long-period comets are smaller and much easier to disrupt than observed htcs. | origin and evolution of short-period comets |
in this paper, we present an analysis of near-infrared spectropolarimetric and velocimetric data of the young m dwarf au mic, collected with spirou at the canada-france-hawaii telescope from 2019 to 2022, mostly within the spirou legacy survey. with these data, we study the large- and small-scale magnetic field of au mic, detected through the unpolarized and circularly polarized zeeman signatures of spectral lines. we find that both are modulated with the stellar rotation period (4.86 d), and evolve on a time-scale of months under differential rotation and intrinsic variability. the small-scale field, estimated from the broadening of spectral lines, reaches 2.61 ± 0.05 kg. the large-scale field, inferred with zeeman-doppler imaging from least-squares deconvolved profiles of circularly polarized and unpolarized spectral lines, is mostly poloidal and axisymmetric, with an average intensity of 550 ± 30 g. we also find that surface differential rotation, as derived from the large-scale field, is ≃30 per cent weaker than that of the sun. we detect the radial velocity (rv) signatures of transiting planets b and c, although dwarfed by activity, and put an upper limit on that of candidate planet d, putatively causing the transit-timing variations of b and c. we also report the detection of the rv signature of a new candidate planet (e) orbiting further out with a period of 33.39 ± 0.10 d, i.e. near the 4:1 resonance with b. the rv signature of e is detected at 6.5σ while those of b and c show up at ≃4σ, yielding masses of $10.2^{+3.9}_{-2.7}$ and $14.2^{+4.8}_{-3.5}$ m⊕ for b and c, and a minimum mass of $35.2^{+6.7}_{-5.4}$ m⊕ for e. | the magnetic field and multiple planets of the young dwarf au mic |
we report the discovery of wasp-189b: an ultra-hot jupiter in a 2.72-d transiting orbit around the $v = 6.6$ a star wasp-189 (hr 5599). we detected periodic dimmings in the star's lightcurve, first with the wasp-south survey facility then with the trappist-south telescope. we confirmed that a planet is the cause of those dimmings via line-profile tomography and radial-velocity measurements using the harps and coralie spectrographs. those reveal wasp-189b to be an ultra-hot jupiter ($m_{\rm p}$ = 2.13 $\pm$ 0.28 $m_{\rm jup}$; $r_{\rm p}$ = 1.374 $\pm$ 0.082 $r_{\rm jup}$) in a polar orbit ($\lambda = 89.3 \pm 1.4^\circ$; $\psi = 90.0 \pm 5.8^\circ$) around a rapidly rotating a6iv-v star ($t_{\rm eff}$ = 8000 $\pm$ 100 k; $v_* \sin i_*$ $\approx$ 100 km\, s$^{-1}$). we calculate a predicted equilibrium temperature of $t_{\rm eql}$ = 2641 $\pm$ 34 k, assuming zero albedo and efficient redistribution, which is the third hottest for the known exoplanets. wasp-189 is the brightest known host of a transiting hot jupiter and the third-brightest known host of any transiting exoplanet. we note that of the eight hot-jupiter systems with $t_{\rm eff}$ $>$ 7000 k, seven have strongly misaligned orbits, and two of the three systems with $t_{\rm eff}$ $\geq$ 8000 k have polar orbits (the third is aligned). | wasp-189b: an ultra-hot jupiter transiting the bright a star hr 5599 in a polar orbit |
the climatological variation of aerosol properties and the planetary boundary layer (pbl) during 2013-2015 over the yangtze river delta (yrd) region were investigated by employing ground-based micro pulse lidar (mpl) and ce-318 sun-photometer observations. combining moderate resolution imaging spectroradiometer (modis) and cloud-aerosol lidar and infrared pathfinder satellite observation (calipso) satellite products, enhanced haze pollution events affected by different types of aerosol over the yrd region were analyzed through vertical structures, spatial distributions, backward trajectories, and the potential source contribution function (pscf) model. the results show that aerosols in the yrd are dominated by fine-mode particles, except in march. the aerosol optical depth (aod) in june and september is higher due to high single scattering albedo (ssa) from hygroscopic growth, but it is lower in july and august due to wet deposition from precipitation. the pbl height (pblh) is greater (means ranging from 1.23 to 1.84 km) and more variable in the warmer months of march to august, due to the stronger diurnal cycle and exchange of heat. northern fine-mode pollutants are brought to the yrd at a height of 1.5 km. the ssa increases, blocking the radiation to the surface, and cooling the surface, thereby weakening turbulence, lowering the pbl, and in turn accelerating the accumulation of pollutants, creating a feedback to the cooling effect. originated from the deserts in xinjiang and inner mongolia, long-range transported dust masses are seen at heights of about 2 km over the yrd region with an ssa440 nm below 0.84, which heat air and raise the pbl, accelerating the diffusion of dust particles. regional transport from biomass-burning spots to the south of the yrd region bring mixed aerosol particles at a height below 1.5 km, resulting in an ssa440 nm below 0.89. during the winter, the accumulation of the local emission layer is facilitated by stable weather conditions, staying within the pbl even below 0.5 km. | aerosol optical characteristics and their vertical distributions under enhanced haze pollution events: effect of the regional transport of different aerosol types over eastern china |
in recent years, there is a growing interest in small satellites for deep space exploration. the current approach for planetary navigation is based on ground-based radiometric tracking. a new era of low-cost small satellites for space exploration will require autonomous deep space navigation. this will decrease the reliance on ground-based tracking and provide a substantial reduction in operational costs because of crowded communication networks. in addition, it will be an enabler for future missions currently impossible. this review investigates available deep space navigation methods from an autonomy perspective, considering trends in proposed deep space small satellite missions. autonomous crosslink radiometric navigation, which is one of the best methods for small satellites due to its simplicity and the use of existing technologies, is studied, including available measurement methods, enabling technologies, and applicability to the currently proposed missions. the main objective of this study is to fill the gap in the scientific literature on the autonomous deep space navigation methods, deeply for crosslink radiometric navigation and to aim at showing the potential advantages that this technique could offer to the missions being analyzed. in this study, a total of 64 proposed deep space small satellite missions have been analyzed found from a variety of sources including journal papers, conference proceedings, and mission websites. in those missions, the most popular destinations are found to be cislunar space and small bodies with the purpose of surface mapping and characterization. even though various autonomous navigation methods have been proposed for those missions, most of them have planned to use the traditional ground-based radiometric tracking for navigation purposes. this study also shows that more than half of the missions can benefit from the crosslink radiometric navigation through the inter-satellite link. | autonomous navigation for deep space small satellites: scientific and technological advances |
cloud liquid water content (lwc) and droplet effective radius (re) have an important influence on cloud physical processes and optical characteristics. the microphysical properties of a three-layer pure liquid stratus were measured by aircraft probes on 26 april 2014 over a coastal region in huanghua, china. vertical variations in aerosol concentration (na), cloud condensation nuclei (ccn) at supersaturation (ss) 0.3%, cloud lwc and cloud re are examined. large na in the size range of 0.1–3 μm and ccn have been found within the planetary boundary layer (pbl) below ~1150 m. however, na and ccn decrease quickly with height and reach a level similar to that over marine locations. corresponding to the vertical distributions of aerosols and ccn, the cloud re is quite small (3.0–6 μm) at heights below 1150 m, large (7–13 μm) at high altitudes. in the pbl cloud layer, cloud re and aerosol na show a negative relationship, while they show a clear positive relationship in the upper layer above pbl with much less aerosol na. it also shows that the relationship between cloud re and aerosol na changes from negative to positive when lwc increases. these results imply that the response of cloud re to aerosol na depends on the combination effects of water-competency and collision-coalescence efficiency among droplets. the vertical structure of aerosol na and cloud re implies potential cautions for the study of aerosol-cloud interaction using aerosol optical depth for cloud layers above the pbl altitude. | a case study of stratus cloud properties using in situ aircraft observations over huanghua, china |
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