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jupiter's atmosphere is enriched in c, n, s, p, ar, kr, and xe with respect to solar abundances by a factor of ∼3. gas giant envelopes are mainly enriched through the dissolution of solids in the atmosphere, and this constant enrichment factor is puzzling since several of the above elements are not expected to have been in the solid phase in jupiter's feeding zone; most seriously, ar and the main carrier of n, n2, only condense at the very low temperatures, 21-26 k, associated with the outer solar nebula. we propose that a plausible solution to the enigma of jupiter's uniform enrichment pattern is that jupiter's core formed exterior to the n2 and ar snowlines, beyond 30 au, resulting in a solar composition core in all volatiles heavier than ne. during envelope accretion and planetesimal bombardment, some of the core mixed in with the envelope, causing the observed enrichment pattern. we show that this scenario naturally produces the observed atmosphere composition, even with substantial pollution from n-poor pebble and planetesimal accretion in jupiter's final feeding zone. we note that giant core formation at large nebular radii is consistent with recent models of gas giant core formation through pebble accretion, which requires the core to form exterior to jupiter's current location to counter rapid inward migration during the core and envelope formation process. if this scenario is common, gas giant core formation may account for many of the gaps observed in protoplanetary disks between 10 s and 100 au. | jupiter's composition suggests its core assembled exterior to the n2 snowline |
the atmosphere of a brown dwarf or extrasolar giant planet controls the spectrum of radiation emitted by the object and regulates its cooling over time. although the study of these atmospheres has been informed by decades of experience modeling stellar and planetary atmospheres, the distinctive characteristics of these objects present unique challenges to forward modeling. in particular, complex chemistry arising from molecule-rich atmospheres, molecular opacity line lists (sometimes running to 10 billion absorption lines or more), multiple cloud-forming condensates, and disequilibrium chemical processes all combine to create a challenging task for any modeling effort. this review describes the process of incorporating these complexities into one-dimensional radiative-convective equilibrium models of substellar objects. we discuss the underlying mathematics as well as the techniques used to model the physics, chemistry, radiative transfer, and other processes relevant to understanding these atmospheres. the review focuses on methods for creating atmosphere models and briefly presents some comparisons of model predictions to data. current challenges in the field and some comments on the future conclude the review. | on the cool side: modeling the atmospheres of brown dwarfs and giant planets |
the origin of life on earth seems to demand a highly reduced early atmosphere, rich in ch4, h2, and nh3, but geological evidence suggests that earth's mantle has always been relatively oxidized and its emissions dominated by co2, h2o, and n2. the paradox can be resolved by exploiting the reducing power inherent in the "late veneer," i.e., material accreted by earth after the moon-forming impact. isotopic evidence indicates that the late veneer consisted of extremely dry, highly reduced inner solar system materials, suggesting that earth's oceans were already present when the late veneer came. the major primary product of reaction between the late veneer's iron and earth's water was h2. ocean-vaporizing impacts generate high pressures and long cooling times that favor ch4 and nh3. impacts too small to vaporize the oceans are much less productive of ch4 and nh3, unless (i) catalysts were available to speed their formation, or (ii) additional reducing power was extracted from pre-existing crustal or mantle materials. the transient h2-ch4 atmospheres evolve photochemically to generate nitrogenated hydrocarbons at rates determined by solar radiation and hydrogen escape, on timescales ranging up to tens of millions of years and with cumulative organic production ranging up to half a kilometer. roughly one ocean of hydrogen escapes. after the methane is gone, the atmosphere is typically h2- and co-rich, with eventual oxidation to co2 rate-limited by water photolysis and hydrogen escape. | creation and evolution of impact-generated reduced atmospheres of early earth |
context. probing the evaporation of exoplanet atmospheres is key to understanding the formation and evolution of exoplanetary systems. the main tracer of evaporation in the uv is the lyman-α transition, which can reveal extended exospheres of neutral hydrogen. recently, the near-infrared (nir) metastable helium triplet (10 833 å) revealed extended thermospheres in several exoplanets. this opens a new window into evaporation.aims: we aim at spectrally resolving the first helium absorption signature detected in the warm saturn wasp-107b with the wide filed camera 3 on board the hubble space telescope (hst/wfc3).methods: we obtained one transit of wasp-107b with carmenes installed on the 3.5 m telescope at the calar alto observatory.results: we detect an excess helium absorption signature of 5.54 ± 0.27% (20σ) in the planet rest frame during the transit. the detection is in agreement with the previous detection achieved with hst/wfc3. the signature shows an excess absorption in the blue part of the lines, suggesting that he i atoms are escaping from the atmosphere of wasp-107b. we interpret the time-series absorption spectra using the 3d eve code. our observations can be explained by combining an extended thermosphere that fills half of the roche lobe and a large exospheric tail sustained by an escape rate of metastable helium of about 106 g s-1. in this scenario, however, the upper atmosphere needs to be subjected to a reduced photoionisation and radiation pressure from the star for the model to match the observations.conclusions: we confirm the presence of helium in the atmosphere of wasp-107b at high confidence. the helium feature is detected from space and from the ground. the ground-based high-resolution signal brings detailed information about the spatial and dynamical structure of the upper atmosphere, and simulations suggest that the he i signature of wasp-107b probes both its thermosphere and exosphere, establishing this signature as a robust probe of exoplanetary upper atmospheres. surveys with nir high-resolution spectrographs (e.g. carmenes, the spectromètre infrarouge (spirou), or the near-infrared planet searcher (nirps)) will deliver a statistical understanding of exoplanet thermospheres and exospheres through the helium triplet. | high-resolution confirmation of an extended helium atmosphere around wasp-107b |
the present-day envelope of gaseous planets is a relic of how these giant planets originated and evolved. measuring their elemental composition therefore presents a powerful opportunity to answer long-standing questions regarding planet formation. obtaining precise observational constraints on the elemental inventory of giant exoplanets has, however, remained challenging owing to the limited simultaneous wavelength coverage of current space-based instruments. here, we present thermal emission observations of the nontransiting hot jupiter τ boo b using the new wide wavelength coverage (0.95-2.50 μm) and high spectral resolution (r = 70,000) cfht/spirou spectrograph. by combining a total of 20 hr of spirou data obtained over five nights in a full atmospheric retrieval framework designed for high-resolution data, we constrain the abundances of all the major oxygen- and carbon-bearing molecules and recover a noninverted temperature structure using a new free-shape, nonparametric temperature-pressure profile retrieval approach. we find a volume mixing ratio of log(co) = - ${2.46}_{-0.29}^{+0.25}$ and a highly depleted water abundance of less than 0.0072 times the expected value for a solar composition envelope. combined with upper limits on the abundances of ch4, co2, hcn, tio, and c2h2, this results in a gas-phase c/h ratio of ${5.85}_{-2.82}^{+4.44}$ × solar, consistent with the value of jupiter, and an envelope c/o ratio robustly greater than 0.60, even when taking into account the oxygen that may be sequestered out of the gas phase. combined, the inferred supersolar c/h, o/h, and c/o ratios on τ boo b support a formation scenario beyond the water snowline in a disk enriched in co owing to pebble drift. | where is the water? jupiter-like c/h ratio but strong h2o depletion found on τ boötis b using spirou |
earth grew through collisions with moon-sized to mars-sized planetary embryos from the inner solar system, but it also accreted material from greater heliocentric distances1,2, including carbonaceous chondrite-like bodies, the likely source of earth's water and highly volatile species3,4. understanding when and how this material was added to earth is critical for constraining the dynamics of terrestrial planet formation and the fundamental processes by which earth became habitable. however, earlier studies inferred very different timescales for the delivery of carbonaceous chondrite-like bodies, depending on assumptions about the nature of earth's building materials5-11. here we show that the mo isotopic composition of earth's primitive mantle falls between those of the non-carbonaceous and carbonaceous reservoirs12-15, and that this observation allows us to quantify the accretion of carbonaceous chondrite-like material to earth independently of assumptions about its building blocks. as most of the mo in the primitive mantle was delivered by late-stage impactors10, our data demonstrate that earth accreted carbonaceous bodies late in its growth history, probably through the moon-forming impact. this late delivery of carbonaceous material probably resulted from an orbital instability of the gas giant planets, and it demonstrates that earth's habitability is strongly tied to the very late stages of its growth. | molybdenum isotopic evidence for the late accretion of outer solar system material to earth |
aims: to date, infrared interferometry at best achieved contrast ratios of a few times 10-4 on bright targets. gravity, with its dual-field mode, is now capable of high contrast observations, enabling the direct observation of exoplanets. we demonstrate the technique on hr 8799, a young planetary system composed of four known giant exoplanets.methods: we used the gravity fringe tracker to lock the fringes on the central star, and integrated off-axis on the hr 8799 e planet situated at 390 mas from the star. data reduction included post-processing to remove the flux leaking from the central star and to extract the coherent flux of the planet. the inferred k band spectrum of the planet has a spectral resolution of 500. we also derive the astrometric position of the planet relative to the star with a precision on the order of 100 μas.results: the gravity astrometric measurement disfavors perfectly coplanar stable orbital solutions. a small adjustment of a few degrees to the orbital inclination of hr 8799 e can resolve the tension, implying that the orbits are close to, but not strictly coplanar. the spectrum, with a signal-to-noise ratio of ≈5 per spectral channel, is compatible with a late-type l brown dwarf. using exo-rem synthetic spectra, we derive a temperature of 1150 ± 50 k and a surface gravity of 104.3 ± 0.3 cm s2. this corresponds to a radius of 1.17-0.11+0.13 rjup and a mass of 10-4+7 mjup, which is an independent confirmation of mass estimates from evolutionary models. our results demonstrate the power of interferometry for the direct detection and spectroscopic study of exoplanets at close angular separations from their stars. the reduced spectrum is 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/l11. based on observations collected at the european organisation for astronomical research in the southern hemisphere, id 60.a-9102(g). | first direct detection of an exoplanet by optical interferometry. astrometry and k-band spectroscopy of hr 8799 e |
isotopic variations usually follow mass-dependent fractionation, meaning that the relative variations in isotopic ratios scale with the difference in mass of the isotopes involved (e.g., δ17o ≈ 0.5×δ18o). in detail, however, the mass dependence of isotopic variations is not always the same, and different natural processes can define distinct slopes in three-isotope diagrams. these variations are subtle, but improvements in analytical capabilities now allow precise measurement of these effects and make it possible to draw inferences about the natural processes that caused them (e.g., reaction kinetics versus equilibrium isotope exchange). some elements, in some sample types, do not conform to the regularities of mass-dependent fractionation. oxygen and sulfur display a rich phenomenology of mass-independent fractionation, documented in the laboratory, in the rock record, and in the modern atmosphere. oxygen in meteorites shows isotopic variations that follow a slope-one line (δ17o ≈ δ18o) whose origin may be associated with co photodissociation. sulfur mass-independent fractionation in ancient sediments provides the tightest constraint on the oxygen partial pressure in the archean and the timing of earth's surface oxygenation. heavier elements also show departures from mass fractionation that can be ascribed to exotic effects associated with chemical reactions such as magnetic effects (e.g., hg) or the nuclear field shift effect (e.g., u or tl). some isotopic variations in meteorites and their constituents cannot be related to the terrestrial composition by any known process, including radiogenic, nucleogenic, and cosmogenic effects. those variations have a nucleosynthetic origin, reflecting the fact that the products of stellar nucleosynthesis were not fully homogenized when the solar system formed. those anomalies are found at all scales, from nanometer-sized presolar grains to bulk terrestrial planets. they can be used to learn about stellar nucleosynthesis, mixing in the solar nebula, and genetic relationships between planetary bodies (e.g., the origin of the moon). they can also confound interpretations based on dating techniques (e.g., 146sm-142nd) when they are misidentified as isotopic variations of radiogenic origin. to summarize, there is a world to explore outside of mass-dependent fractionation whose impact is promised to expand as analytical capabilities to measure ever-subtler isotopic anomalies on ever-smaller samples continue to improve. | mass fractionation laws, mass-independent effects, and isotopic anomalies |
a relation between the mass accretion rate onto the central young star and the mass of the surrounding protoplanetary disk has long been theoretically predicted and observationally sought. for the first time, we have accurately and homogeneously determined the photospheric parameters, mass accretion rate, and disk mass for an essentially complete sample of young stars with disks in the lupus clouds. our work combines the results of surveys conducted with vlt/x-shooter and alma. with this dataset we are able to test a basic prediction of viscous accretion theory, the existence of a linear relation between the mass accretion rate onto the central star and the total disk mass. we find a correlation between the mass accretion rate and the disk dust mass, with a ratio that is roughly consistent with the expected viscous timescale when assuming an interstellar medium gas-to-dust ratio. this confirms that mass accretion rates are related to the properties of the outer disk. we find no correlation between mass accretion rates and the disk mass measured by co isotopologues emission lines, possibly owing to the small number of measured disk gas masses. this suggests that the mm-sized dust mass better traces the total disk mass and that masses derived from co may be underestimated, at least in some cases. | evidence for a correlation between mass accretion rates onto young stars and the mass of their protoplanetary disks |
we searched for superflares on solar-type stars using kepler data with 1-min sampling in order to detect superflares with a short duration. we found 187 superflares on 23 solar-type stars whose bolometric energy ranges from the order of 1032 to 1036 erg. some superflares show multiple peaks with the peak separation of the order of 100 to 1,000 s which is comparable to the periods of quasi-periodic pulsations in solar and stellar flares. using these new data combined with the results from the data with 30-min sampling, we found that the occurrence frequency (dn/de) of superflares as a function of flare energy ( e) shows the power-law distribution (dn/de∝ e - α ) with α∼-1.5 for 1033< e<1036 erg which is consistent with the previous results. the average occurrence rate of superflares with the energy of 1033 erg which is equivalent to x100 solar flares is about once in 500 to 600 years. the upper limit of energy released by superflares is basically comparable to a fraction of the magnetic energy stored near starspots which is estimated from the photometry. we also found that the duration of superflares ( τ) increases with the flare energy ( e) as τ∝ e 0.39 ± 0.03. this can be explained if we assume the time scale of flares is determined by the alfvén time. | statistical properties of superflares on solar-type stars based on 1-min cadence data |
we present exoplanet occurrence rates estimated with approximate bayesian computation for planets with radii between 0.5 and 16 r⊕ and orbital periods between 0.78 and 400 days orbiting fgk dwarf stars. we base our results on an independent planet catalog compiled from our search of all ∼200,000 stars observed over the kepler mission, with precise planetary radii supplemented by gaia dr2-incorporated stellar radii. we take into account detection and vetting efficiency, planet radius uncertainty, and reliability against transit-like noise signals in the data. by analyzing our fgk occurrence rates as well as those computed after separating f-, g-, and k-type stars, we explore dependencies on stellar effective temperature, planet radius, and orbital period. we reveal new characteristics of the photoevaporation-driven "radius gap" between ∼1.5 and 2 r⊕, indicating that the bimodal distribution previously revealed for p < 100 days exists only over a much narrower range of orbital periods, above which sub-neptunes dominate and below which super-earths dominate. finally, we provide several estimates of the "eta-earth" value—the frequency of potentially habitable, rocky planets orbiting sun-like stars. for planets with sizes 0.75-1.5 r⊕ orbiting in a conservatively defined habitable zone (0.99-1.70 au) around g-type stars, we place an upper limit (84.1th percentile) of <0.18 planets per star. | searching the entirety of kepler data. ii. occurrence rate estimates for fgk stars |
aims: we study the evolution of stellar rotation and wind properties for low-mass main-sequence stars. our aim is to use rotational evolution models to constrain the mass loss rates in stellar winds and to predict how their properties evolve with time on the main-sequence.methods: we construct a rotational evolution model that is driven by observed rotational distributions of young stellar clusters. fitting the free parameters in our model allows us to predict how wind mass loss rate depends on stellar mass, radius, and rotation. we couple the results to the wind model developed in paper i of this series to predict how wind properties evolve on the main-sequence.results: we estimate that wind mass loss rate scales with stellar parameters as ṁ⋆ ∝ r⋆2 ω⋆1.33 m⋆-3.36. we estimate that at young ages, the solar wind likely had a mass loss rate that is an order of magnitude higher than that of the current solar wind. this leads to the wind having a higher density at younger ages; however, the magnitude of this change depends strongly on how we scale wind temperature. due to the spread in rotation rates, young stars show a large range of wind properties at a given age. this spread in wind properties disappears as the stars age.conclusions: there is a large uncertainty in our knowledge of the evolution of stellar winds on the main-sequence, due both to our lack of knowledge of stellar winds and the large spread in rotation rates at young ages. given the sensitivity of planetary atmospheres to stellar wind and radiation conditions, these uncertainties can be significant for our understanding of the evolution of planetary environments. | stellar winds on the main-sequence. ii. the evolution of rotation and winds |
using data taken with the keck planet finder spectrograph we calculate a host e(b-v) extinction of 0.031±0.006. | host extinction of sn2023ixf |
the magnitude and distribution of net primary production (npp) in the coastal ocean remains poorly constrained, particularly for shallow marine vegetation. here, using a compilation of in situ annual npp measurements across >400 sites in 72 geographic ecoregions, we provide global predictions of the productivity of seaweed habitats, which form the largest vegetated coastal biome on the planet. we find that seaweed npp is strongly coupled to climatic variables, peaks at temperate latitudes, and is dominated by forests of large brown seaweeds. seaweed forests exhibit exceptionally high per-area production rates (a global average of 656 and 1711 gc m −2 year −1 in the subtidal and intertidal, respectively), being up to 10 times higher than coastal phytoplankton in temperate and polar seas. our results show that seaweed npp is a strong driver of production in the coastal ocean and call for its integration in the oceanic carbon cycle, where it has traditionally been overlooked. global estimates show that seaweed habitats are a strong driver of productivity in the coastal ocean. | global seaweed productivity |
the outer solar system origins survey (ossos), a wide-field imaging program in 2013-2017 with the canada-france-hawaii telescope, surveyed 155 deg2 of sky to depths of mr= 24.1-25.2. we present 838 outer solar system discoveries that are entirely free of ephemeris bias. this increases the inventory of trans-neptunian objects (tnos) with accurately known orbits by nearly 50%. each minor planet has 20-60 gaia/pan-starrs-calibrated astrometric measurements made over 2-5 oppositions, which allows accurate classification of their orbits within the trans-neptunian dynamical populations. the populations orbiting in mean-motion resonance with neptune are key to understanding neptune’s early migration. our 313 resonant tnos, including 132 plutinos, triple the available characterized sample and include new occupancy of distant resonances out to semimajor axis a ∼ 130 au. ossos doubles the known population of the nonresonant kuiper belt, providing 436 tnos in this region, all with exceptionally high-quality orbits of a uncertainty σa≤ 0.1% they show that the belt exists from a ≳ 37 au, with a lower perihelion bound of 35 au. we confirm the presence of a concentrated low-inclination a ≃ 44 au “kernel” population and a dynamically cold population extending beyond the 2:1 resonance. we finely quantify the survey’s observational biases. our survey simulator provides a straightforward way to impose these biases on models of the trans-neptunian orbit distributions, allowing statistical comparison to the discoveries. the ossos tnos, unprecedented in their orbital precision for the size of the sample, are ideal for testing concepts of the history of giant planet migration in the solar system. | ossos. vii. 800+ trans-neptunian objects—the complete data release |
we confirm and characterize a close-in ({p}{{orb}} = 5.425 days), super-neptune sized ({5.04}-0.37+0.34 {r}\oplus ) planet transiting k2-33 (2mass j16101473-1919095), a late-type (m3) pre-main-sequence (11 myr old) star in the upper scorpius subgroup of the scorpius-centaurus ob association. the host star has the kinematics of a member of the upper scorpius ob association, and its spectrum contains lithium absorption, an unambiguous sign of youth (\lt 20 myr) in late-type dwarfs. we combine photometry from k2 and the ground-based mearth project to refine the planet’s properties and constrain the host star’s density. we determine k2-33’s bolometric flux and effective temperature from moderate-resolution spectra. by utilizing isochrones that include the effects of magnetic fields, we derive a precise radius (6%-7%) and mass (16%) for the host star, and a stellar age consistent with the established value for upper scorpius. follow-up high-resolution imaging and doppler spectroscopy confirm that the transiting object is not a stellar companion or a background eclipsing binary blended with the target. the shape of the transit, the constancy of the transit depth and periodicity over 1.5 yr, and the independence with wavelength rule out stellar variability or a dust cloud or debris disk partially occulting the star as the source of the signal; we conclude that it must instead be planetary in origin. the existence of k2-33b suggests that close-in planets can form in situ or migrate within ∼10 myr, e.g., via interactions with a disk, and that long-timescale dynamical migration such as by lidov-kozai or planet-planet scattering is not responsible for all short-period planets. | zodiacal exoplanets in time (zeit). iii. a short-period planet orbiting a pre-main-sequence star in the upper scorpius ob association |
theories of the formation and early evolution of planetary systems postulate that planets are born in circumstellar disks, and undergo radial migration during and after dissipation of the dust and gas disk from which they formed. the precise ages of meteorites indicate that planetesimals—the building blocks of planets—are produced within the first million years of a star’s life. fully formed planets are frequently detected on short orbital periods around mature stars. some theories suggest that the in situ formation of planets close to their host stars is unlikely and that the existence of such planets is therefore evidence of large-scale migration. other theories posit that planet assembly at small orbital separations may be common. here we report a newly born, transiting planet orbiting its star with a period of 5.4 days. the planet is 50 per cent larger than neptune, and its mass is less than 3.6 times that of jupiter (at 99.7 per cent confidence), with a true mass likely to be similar to that of neptune. the star is 5-10 million years old and has a tenuous dust disk extending outward from about twice the earth-sun separation, in addition to the fully formed planet located at less than one-twentieth of the earth-sun separation. | a neptune-sized transiting planet closely orbiting a 5-10-million-year-old star |
high resolution transit spectroscopy has proven to be a reliable technique for the characterization of the chemical composition of exoplanet atmospheres. taking advantage of the broad spectral coverage of the carmenes spectrograph, we initiated a survey aimed at characterizing a broad range of planetary systems. here, we report our observations of three transits of gj 3470 b with carmenes in search of he (23s) absorption. on one of the nights, the he i region was heavily contaminated by oh- telluric emission and, thus, it was not useful for our purposes. the remaining two nights had a very different signal-to-noise ratio (s/n) due to weather. they both indicate the presence of he (23s) absorption in the transmission spectrum of gj 3470 b, although a statistically valid detection can only be claimed for the night with higher s/n. for that night, we retrieved a 1.5 ± 0.3% absorption depth, translating into a rp(λ)/rp = 1.15 ± 0.14 at this wavelength. spectro-photometric light curves for this same night also indicate the presence of extra absorption during the planetary transit with a consistent absorption depth. the he (23s) absorption is modeled in detail using a radiative transfer code, and the results of our modeling efforts are compared to the observations. we find that the mass-loss rate, ṁ, is confined to a range of 3 × 1010 g s-1 for t = 6000 k to 10 × 1010 g s-1 for t = 9000 k. we discuss the physical mechanisms and implications of the he i detection in gj 3470 b and put it in context as compared to similar detections and non-detections in other neptune-size planets. we also present improved stellar and planetary parameter determinations based on our visible and near-infrared observations. | a he i upper atmosphere around the warm neptune gj 3470 b |
using current technology, gravitational microlensing is the only method that can measure planet masses over the full parameter space of planet and stellar-host masses and at a broad range of planet-host separations. i present a comprehensive program to transform the $\sim 150$ planet/host mass ratio measurements from the first 6 full seasons of the kmtnet survey into planet mass measurements via late-time adaptive optics (ao) imaging on 30m-class telescopes. this program will enable measurements of the overall planet mass function, the planet frequency as a function of galactic environment and the planet mass functions within different environments. i analyze a broad range of discrete and continuous degeneracies as well as various false positives and false negatives, and i present a variety of methods to resolve these. i analyze the propagation from measurement uncertainties to mass and distance errors and show that these present the greatest difficulties for host masses $0.13\lesssim(m/m_\odot)\lesssim 0.4$, i.e., fully convective stars supported by the ideal gas law, and for very nearby hosts. while work can begin later this decade using ao on current telescopes, of order 90% of the target sample must await 30m-class ao. i present extensive tables with information that is useful to plan observations of more than 100 of these planets and provide additional notes for a majority of these. applying the same approach to two earlier surveys with 6 and 8 planets, respectively, i find that 11 of these 14 planets already have mass measurements by a variety of techniques. these provide suggestive evidence that planet frequency may be higher for nearby stars, $d_l\lesssim 4$ kpc compared to those in or near the galactic bulge. finally, i analyze the prospects for making the planet mass-function measurement for the case that current astronomical capabilities are seriously degraded. | masada: from microlensing planet mass-ratio function to planet mass function |
to identify promising exoplanets for atmospheric characterization and to make the best use of observational data, a thorough understanding of their atmospheres is needed. three-dimensional general circulation models (gcms) are one of the most comprehensive tools available for this task and will be used to interpret observations of temperate rocky exoplanets. due to parameterization choices made in gcms, they can produce different results, even for the same planet. employing four widely used exoplanetary gcms-exocam, lmd-g, rocke-3d, and the um-we continue the trappist-1 habitable atmosphere intercomparison by modeling aquaplanet climates of trappist-1e with a moist atmosphere dominated by either nitrogen or carbon dioxide. although the gcms disagree on the details of the simulated regimes, they all predict a temperate climate with neither of the two cases pushed out of the habitable state. nevertheless, the intermodel spread in the global mean surface temperature is nonnegligible: 14 k and 24 k in the nitrogen- and carbon dioxide-dominated case, respectively. we find substantial intermodel differences in moist variables, with the smallest amount of clouds in lmd-generic and the largest in rocke-3d. exocam predicts the warmest climate for both cases and thus has the highest water vapor content and the largest amount and variability of cloud condensate. the um tends to produce colder conditions, especially in the nitrogen-dominated case due to a strong negative cloud radiative effect on the day side of trappist-1e. our study highlights various biases of gcms and emphasizes the importance of not relying solely on one model to understand exoplanet climates. | the trappist-1 habitable atmosphere intercomparison (thai). ii. moist cases-the two waterworlds |
we present updated radial-velocity (rv) analyses of the au mic system. au mic is a young (22 myr) early-m dwarf known to host two transiting planets-pb~ 8.46 days, ${r}_{b}={4.38}_{-0.18}^{+0.18}\ {r}_{\oplus }$ , pc~ 18.86 days, ${r}_{c}={3.51}_{-0.16}^{+0.16}\ {r}_{\oplus }$ . with visible rvs from calar alto high-resolution search for m dwarfs with exo-earths with near-infrared and optical echelle spectrographs (carmenes)-vis, chiron, harps, hires, minerva-australis, and tillinghast reflector echelle spectrograph, as well as near-infrared (nir) rvs from carmenes-nir, cshell, ird, ishell, nirspec, and spirou, we provide a 5σ upper limit to the mass of au mic c of mc≤ 20.13 m ⊕ and present a refined mass of au mic b of ${m}_{b}={20.12}_{-1.57}^{+1.72}\ {m}_{\oplus }$ . used in our analyses is a new rv modeling toolkit to exploit the wavelength dependence of stellar activity present in our rvs via wavelength-dependent gaussian processes. by obtaining near-simultaneous visible and near-infrared rvs, we also compute the temporal evolution of rv "color" and introduce a regressional method to aid in isolating keplerian from stellar activity signals when modeling rvs in future works. using a multiwavelength gaussian process model, we demonstrate the ability to recover injected planets at 5σ significance with semi-amplitudes down to ≈10 m s-1 with a known ephemeris, more than an order of magnitude below the stellar activity amplitude. however, we find that the accuracy of the recovered semi-amplitudes is ~50% for such signals with our model. | diving beneath the sea of stellar activity: chromatic radial velocities of the young au mic planetary system |
capturing planets in the act of losing their atmospheres provides rare opportunities to probe their evolution history. this analysis has been enabled by observations of the helium triplet at 10,833 angstrom, but past studies have focused on the narrow time window right around the planet's optical transit. we monitored the hot jupiter hat-p-32 b using high-resolution spectroscopy from the hobby-eberly telescope covering the planet's full orbit. we detected helium escaping hat-p-32 b at a 14σ significance,with extended leading and trailing tails spanning a projected length over 53 times the planet's radius. these tails are among the largest known structures associated with an exoplanet. we interpret our observations using three-dimensional hydrodynamic simulations, which predict roche lobe overflow with extended tails along the planet's orbital path. long-baseline monitoring of the hat-p-32ab system reveals helium escaping through tidal tails 50 times the size of the planet. | giant tidal tails of helium escaping the hot jupiter hat-p-32 b |
the dependence of the mass accretion rate on the stellar properties is a key constraint for star formation and disk evolution studies. here we present a study of a sample of stars in the chamaeleon i star-forming region carried out using spectra taken with the eso vlt/x-shooter spectrograph. the sample is nearly complete down to stellar masses (m⋆) 0.1 m⊙ for the young stars still harboring a disk in this region. we derive the stellar and accretion parameters using a self-consistent method to fit the broadband flux-calibrated medium resolution spectrum. the correlation between accretion luminosity to stellar luminosity, and of mass accretion rate to stellar mass in the logarithmic plane yields slopes of 1.9 ± 0.1 and 2.3 ± 0.3, respectively. these slopes and the accretion rates are consistent with previous results in various star-forming regions and with different theoretical frameworks. however, we find that a broken power-law fit, with a steeper slope for stellar luminosity lower than 0.45 l⊙ and for stellar masses lower than 0.3 m⊙ is slightly preferred according to different statistical tests, but the single power-law model is not excluded. the steeper relation for lower mass stars can be interpreted as a faster evolution in the past for accretion in disks around these objects, or as different accretion regimes in different stellar mass ranges. finally, we find two regions on the mass accretion versus stellar mass plane that are empty of objects: one region at high mass accretion rates and low stellar masses, which is related to the steeper dependence of the two parameters we derived. the second region is located just above the observational limits imposed by chromospheric emission, at m⋆ 0.3 - 0.4 m⊙. these are typical masses where photoevaporation is known to be effective. the mass accretion rates of this region are 10-10m⊙/yr, which is compatible with the value expected for photoevaporation to rapidly dissipate the inner disk. this work is based on observations made with eso telescopes at the paranal observatory under programme id 090.c-0253 and 095.c-0378. | x-shooter study of accretion in chamaeleon i. ii. a steeper increase of accretion with stellar mass for very low-mass stars? |
wide-field high-precision photometric surveys such as kepler have produced reams of data suitable for investigating stellar magnetic activity of cooler stars. starspot activity produces quasi-sinusoidal light curves whose phase and amplitude vary as active regions grow and decay over time. here we investigate, first, whether there is a correlation between the size of starspots - assumed to be related to the amplitude of the sinusoid - and their decay time-scale and, secondly, whether any such correlation depends on the stellar effective temperature. to determine this, we computed the auto-correlation functions of the light curves of samples of stars from kepler and fitted them with apodised periodic functions. the light-curve amplitudes, representing spot size, were measured from the root-mean-squared scatter of the normalized light curves. we used a monte carlo markov chain to measure the periods and decay time-scales of the light curves. the results show a correlation between the decay time of starspots and their inferred size. the decay time also depends strongly on the temperature of the star. cooler stars have spots that last much longer, in particular for stars with longer rotational periods. this is consistent with current theories of diffusive mechanisms causing starspot decay. we also find that the sun is not unusually quiet for its spectral type - stars with solar-type rotation periods and temperatures tend to have (comparatively) smaller starspots than stars with mid-g or later spectral types. | a kepler study of starspot lifetimes with respect to light-curve amplitude and spectral type |
groundwater is by far the largest unfrozen freshwater resource on the planet. it plays a critical role as the bottom of the hydrologic cycle, redistributing water in the subsurface and supporting plants and surface water bodies. however, groundwater has historically been excluded or greatly simplified in global models. in recent years, there has been an international push to develop global scale groundwater modeling and analysis. this progress has provided some critical first steps. still, much additional work will be needed to achieve a consistent global groundwater framework that interacts seamlessly with observational datasets and other earth system and global circulation models. here we outline a vision for a global groundwater platform for groundwater monitoring and prediction and identify the key technological and data challenges that are currently limiting progress. any global platform of this type must be interdisciplinary and cannot be achieved by the groundwater modeling community in isolation. therefore, we also provide a high-level overview of the groundwater system, approaches to groundwater modeling and the current state of global groundwater representations, such that readers of all backgrounds can engage in this challenge. | global groundwater modeling and monitoring: opportunities and challenges |
context. methods used to detect giant exoplanets can be broadly divided into two categories: indirect and direct. indirect methods are more sensitive to planets with a small orbital period, whereas direct detection is more sensitive to planets orbiting at a large distance from their host star. this dichotomy makes it difficult to combine the two techniques on a single target at once.aims: simultaneous measurements made by direct and indirect techniques offer the possibility of determining the mass and luminosity of planets and a method of testing formation models. here, we aim to show how long-baseline interferometric observations guided by radial-velocity can be used in such a way.methods: we observed the recently-discovered giant planet β pictoris c with gravity, mounted on the very large telescope interferometer.results: this study constitutes the first direct confirmation of a planet discovered through radial velocity. we find that the planet has a temperature of t = 1250 ± 50 k and a dynamical mass of m = 8.2 ± 0.8 mjup. at 18.5 ± 2.5 myr, this puts β pic c close to a `hot start' track, which is usually associated with formation via disk instability. conversely, the planet orbits at a distance of 2.7 au, which is too close for disk instability to occur. the low apparent magnitude (mk = 14.3 ± 0.1) favours a core accretion scenario.conclusions: we suggest that this apparent contradiction is a sign of hot core accretion, for example, due to the mass of the planetary core or the existence of a high-temperature accretion shock during formation. | direct confirmation of the radial-velocity planet β pictoris c |
meteoroid impacts shape planetary surfaces by forming new craters and alter atmospheric composition. during atmospheric entry and impact on the ground, meteoroids excite transient acoustic and seismic waves. however, new crater formation and the associated impact-induced mechanical waves have yet to be observed jointly beyond earth. here we report observations of seismic and acoustic waves from the nasa insight lander's seismometer that we link to four meteoroid impact events on mars observed in spacecraft imagery. we analysed arrival times and polarization of seismic and acoustic waves to estimate impact locations, which were subsequently confirmed by orbital imaging of the associated craters. crater dimensions and estimates of meteoroid trajectories are consistent with waveform modelling of the recorded seismograms. with identified seismic sources, the seismic waves can be used to constrain the structure of the martian interior, corroborating previous crustal structure models, and constrain scaling relationships between the distance and amplitude of impact-generated seismic waves on mars, supporting a link between the seismic moment of impacts and the vertical impactor momentum. our findings demonstrate the capability of planetary seismology to identify impact-generated seismic sources and constrain both impact processes and planetary interiors. | newly formed craters on mars located using seismic and acoustic wave data from insight |
climate change has emerged as an important issue ever to confront mankind. this concern emerges from the fact that our day-to-day activities are leading to impacts on the earth's atmosphere that has the potential to significantly alter the planet's shield and radiation balance. developing countries particularly whose income is particularly derived from agricultural activities are at the forefront of bearing repercussions due to changing climate. the present study is an effort to analyze the changing trends of precipitation and temperature variables in kashmir valley along different elevation zones in the north western part of india. as the kashmir valley has a rich repository of glaciers with its annual share of precipitation, slight change in the temperature and precipitation regime has far reaching environmental and economic consequences. the results from indian meteorological department (imd) data of the period 1980-2014 reveals that the annual mean temperature of kashmir valley has increased significantly. accelerated warming has been observed during 1980-2014, with intense warming in the recent years (2001-2014). during the period 1980-2014, steeper increase, in annual mean maximum temperature than annual mean minimum temperature, has been observed. in addition, mean maximum temperature in plain regions has shown higher rate of increase when compared with mountainous areas. in case of mean minimum temperature, mountainous regions have shown higher rate of increase. analysis of precipitation data for the same period shows a decreasing trend with mountainous regions having the highest rate of decrease which can be quite hazardous for the fragile mountain environment of the kashmir valley housing a large number of glaciers. | temperature and precipitation trends in kashmir valley, north western himalayas |
vertical wind shear (vws) is one of the key meteorological factors in modulating ground-level particulate matter with an aerodynamic diameter of 2.5 µm or less (pm2.5). due to the lack of high-resolution vertical wind measurements, how the vws affects ground-level pm2.5 remains highly debated. here we employed the wind profiling observations from the fine-time-resolution radar wind profiler (rwp), together with hourly ground-level pm2.5 measurements, to explore the wind features in the planetary boundary layer (pbl) and their association with aerosols in beijing for the period from december 1, 2018, to february 28, 2019. overall, southerly wind anomalies almost dominated throughout the whole pbl or even beyond the pbl under polluted conditions during the course of a day, as totally opposed to the northerly wind anomalies in the pbl under clean conditions. besides, the ground-level pm2.5 pollution exhibited a strong dependence on the vws. a much weaker vws was observed in the lower part of the pbl under polluted conditions, compared with that under clean conditions, which could be due to the strong ground-level pm2.5 accumulation induced by weak vertical mixing in the pbl. notably, weak northbound transboundary pm2.5 pollution mainly appeared within the pbl, where relatively small vws dominated. above the pbl, strong northerlies winds also favored the long-range transport of aerosols, which in turn deteriorated the air quality in beijing as well. this was well corroborated by the synoptic-scale circulation and backward trajectory analysis. therefore, we argued here that not only the wind speed in the vertical but the vws were important for the investigation of aerosol pollution formation mechanism in beijing. also, our findings offer wider insights into the role of vws from rwp in modulating the variation of pm2.5, which deserves explicit consideration in the forecast of air quality in the future. | vertica wind shear modulates particulate matter pollutions: a perspective from radar wind profiler observations in beijing, china |
it has long been recognized that earth and other differentiated planetary bodies are chemically fractionated compared to primitive, chondritic meteorites and, by inference, the primordial disk from which they formed. however, it is not known whether the notable volatile depletions of planetary bodies are a consequence of accretion or inherited from prior nebular fractionation. the isotopic compositions of the main constituents of planetary bodies can contribute to this debate. here we develop an analytical approach that corrects a major cause of measurement inaccuracy inherent in conventional methods, and show that all differentiated bodies have isotopically heavier magnesium compositions than chondritic meteorites. we argue that possible magnesium isotope fractionation during condensation of the solar nebula, core formation and silicate differentiation cannot explain these observations. however, isotopic fractionation between liquid and vapour, followed by vapour escape during accretionary growth of planetesimals, generates appropriate residual compositions. our modelling implies that the isotopic compositions of magnesium, silicon and iron, and the relative abundances of the major elements of earth and other planetary bodies, are a natural consequence of substantial (about 40 per cent by mass) vapour loss from growing planetesimals by this mechanism. | magnesium isotope evidence that accretional vapour loss shapes planetary compositions |
generative deep learning has sparked a new wave of super-resolution (sr) algorithms that enhance single images with impressive aesthetic results, albeit with imaginary details. multi-frame super-resolution (mfsr) offers a more grounded approach to the ill-posed problem, by conditioning on multiple low-resolution views. this is important for satellite monitoring of human impact on the planet -- from deforestation, to human rights violations -- that depend on reliable imagery. to this end, we present highres-net, the first deep learning approach to mfsr that learns its sub-tasks in an end-to-end fashion: (i) co-registration, (ii) fusion, (iii) up-sampling, and (iv) registration-at-the-loss. co-registration of low-resolution views is learned implicitly through a reference-frame channel, with no explicit registration mechanism. we learn a global fusion operator that is applied recursively on an arbitrary number of low-resolution pairs. we introduce a registered loss, by learning to align the sr output to a ground-truth through shiftnet. we show that by learning deep representations of multiple views, we can super-resolve low-resolution signals and enhance earth observation data at scale. our approach recently topped the european space agency's mfsr competition on real-world satellite imagery. | highres-net: recursive fusion for multi-frame super-resolution of satellite imagery |
low-mass stars show evidence of vigorous magnetic activity in the form of large flares and coronal mass ejections. such space weather events may have important ramifications for the habitability and observational fingerprints of exoplanetary atmospheres. here, using a suite of three-dimensional coupled chemistry-climate model simulations, we explore effects of time-dependent stellar activity on rocky planet atmospheres orbiting g, k and m dwarf stars. we employ observed data from the muscles campaign and the transiting exoplanet survey satellite and test a range of rotation period, magnetic field strength and flare frequency assumptions. we find that recurring flares drive the atmospheres of planets around k and m dwarfs into chemical equilibria that substantially deviate from their pre-flare regimes, whereas the atmospheres of g dwarf planets quickly return to their baseline states. interestingly, simulated o2-poor and o2-rich atmospheres experiencing flares produce similar mesospheric nitric oxide abundances, suggesting that stellar flares can highlight otherwise undetectable chemical species. applying a radiative transfer model to our chemistry-climate model results, we find that flare-driven transmission features of bio-indicating chemical species, such as nitrogen dioxide, nitrous oxide and nitric acid, show particular promise for detection by future instruments. | persistence of flare-driven atmospheric chemistry on rocky habitable zone worlds |
m dwarf stars are known for their vigorous flaring. this flaring could impact the climate of orbiting planets, making it important to characterize m dwarf flares at the short wavelengths that drive atmospheric chemistry and escape. we conducted a far-ultraviolet flare survey of six m dwarfs from the recent muscles (measurements of the ultraviolet spectral characteristics of low-mass exoplanetary systems) observations, as well as four highly active m dwarfs with archival data. when comparing absolute flare energies, we found the active-m-star flares to be about 10× more energetic than inactive-m-star flares. however, when flare energies were normalized by the star’s quiescent flux, the active and inactive samples exhibited identical flare distributions, with a power-law index of -{0.76}-0.1+0.09 (cumulative distribution). the rate and distribution of flares are such that they could dominate the fuv energy budget of m dwarfs, assuming the same distribution holds to flares as energetic as those cataloged by kepler and ground-based surveys. we used the observed events to create an idealized model flare with realistic spectral and temporal energy budgets to be used in photochemical simulations of exoplanet atmospheres. applied to our own simulation of direct photolysis by photons alone (no particles), we find that the most energetic observed flares have little effect on an earth-like atmosphere, photolyzing ∼0.01% of the total o3 column. the observations were too limited temporally (73 hr cumulative exposure) to catch rare, highly energetic flares. those that the power-law fit predicts occur monthly would photolyze ∼1% of the o3 column and those it predicts occur yearly would photolyze the full o3 column. whether such energetic flares occur at the rate predicted is an open question. | the muscles treasury survey. v. fuv flares on active and inactive m dwarfs |
limb darkening is fundamental in determining transit light-curve shapes, and is typically modelled by a variety of laws that parametrize the intensity profile of the star that is being transited. confronted with a transit light curve, some authors fix the parameters of these laws, the so-called limb darkening coefficients (ldcs), while others prefer to let them float in the light-curve fitting procedure. which of these is the best strategy, however, is still unclear, as well as how and by how much each of these can bias the retrieved transit parameters. in this work we attempt to clarify those points by first recalculating these ldcs, comparing them to measured values from kepler transit light curves using an algorithm that takes into account uncertainties in both the geometry of the transit and the parameters of the stellar host. we show there are significant departures from predicted model values, suggesting that our understanding of limb darkening still needs to improve. then, we show through simulations that if one uses the quadratic limb darkening law to parametrize limb darkening, fixing and fitting the ldcs can lead to significant biases - up to ∼3 and ∼1 per cent in rp/r*, respectively - which are important for several confirmed and candidate exoplanets. we conclude that, in this case, the best approach is to let the ldcs be free in the fitting procedure. strategies to avoid biases in data from present and future missions involving high precision measurements of transit parameters are described. | limb darkening and exoplanets: testing stellar model atmospheres and identifying biases in transit parameters |
sudden stratospheric warming (ssw) events have received increased attention since their impacts on the troposphere became evident recently. studies of ssw usually focus on polar stratospheric conditions; however, understanding the global impact of these events requires studying them from a wider perspective. case studies are used to clarify the characteristics of the stratosphere-troposphere dynamical coupling, and the meridional extent of the phenomena associated with ssw. results show that differences in the recovery phase can be used to classify ssw events into two types. the first is the absorbing type of ssw, which has a longer timescale as well as a larger meridional extent due to the persistent incoming planetary waves from the troposphere. the absorbing type of ssw is related to the annular mode on the surface through poleward and downward migration of the deceleration region of the polar night jet. the other is the reflecting type. this is characterized by a quick termination of the warming episode due to the reflection of planetary waves in the stratosphere, which leads to an amplification of tropospheric planetary waves inducing strong westerlies over the north atlantic and blocking over the north pacific sector. differences in the tropospheric impact of the absorbing and reflecting ssws are also confirmed with composite analysis of 22 major ssws. | absorbing and reflecting sudden stratospheric warming events and their relationship with tropospheric circulation |
identifying unequivocal signs of life on mars is one of the most important objectives for sending missions to the red planet. here we report red stone, a 163-100 my alluvial fan-fan delta that formed under arid conditions in the atacama desert, rich in hematite and mudstones containing clays such as vermiculite and smectites, and therefore geologically analogous to mars. we show that red stone samples display an important number of microorganisms with an unusual high rate of phylogenetic indeterminacy, what we refer to as "dark microbiome", and a mix of biosignatures from extant and ancient microorganisms that can be barely detected with state-of-the-art laboratory equipment. our analyses by testbed instruments that are on or will be sent to mars unveil that although the mineralogy of red stone matches that detected by ground-based instruments on the red planet, similarly low levels of organics will be hard, if not impossible to detect in martian rocks depending on the instrument and technique used. our results stress the importance in returning samples to earth for conclusively addressing whether life ever existed on mars. | dark microbiome and extremely low organics in atacama fossil delta unveil mars life detection limits |
megacities are major sources of anthropogenic fossil fuel co2 (ffco2) emissions. the spatial extents of these large urban systems cover areas of 10 000 km2 or more with complex topography and changing landscapes. we present a high-resolution land-atmosphere modelling system for urban co2 emissions over the los angeles (la) megacity area. the weather research and forecasting (wrf)-chem model was coupled to a very high-resolution ffco2 emission product, hestia-la, to simulate atmospheric co2 concentrations across the la megacity at spatial resolutions as fine as ∼ 1 km. we evaluated multiple wrf configurations, selecting one that minimized errors in wind speed, wind direction, and boundary layer height as evaluated by its performance against meteorological data collected during the calnex-la campaign (may-june 2010). our results show no significant difference between moderate-resolution (4 km) and high-resolution (1.3 km) simulations when evaluated against surface meteorological data, but the high-resolution configurations better resolved planetary boundary layer heights and vertical gradients in the horizontal mean winds. we coupled our wrf configuration with the vulcan 2.2 (10 km resolution) and hestia-la (1.3 km resolution) fossil fuel co2 emission products to evaluate the impact of the spatial resolution of the co2 emission products and the meteorological transport model on the representation of spatiotemporal variability in simulated atmospheric co2 concentrations. we find that high spatial resolution in the fossil fuel co2 emissions is more important than in the atmospheric model to capture co2 concentration variability across the la megacity. finally, we present a novel approach that employs simultaneous correlations of the simulated atmospheric co2 fields to qualitatively evaluate the greenhouse gas measurement network over the la megacity. spatial correlations in the atmospheric co2 fields reflect the coverage of individual measurement sites when a statistically significant number of sites observe emissions from a specific source or location. we conclude that elevated atmospheric co2 concentrations over the la megacity are composed of multiple fine-scale plumes rather than a single homogenous urban dome. furthermore, we conclude that ffco2 emissions monitoring in the la megacity requires ffco2 emissions modelling with ∼ 1 km resolution because coarser-resolution emissions modelling tends to overestimate the observational constraints on the emissions estimates. | los angeles megacity: a high-resolution land-atmosphere modelling system for urban co2 emissions |
primary production by marine phytoplankton is one of the largest fluxes of carbon on our planet. in the past few decades, considerable progress has been made in estimating global primary production at high spatial and temporal scales by combining in situ measurements of primary production with remote-sensing observations of phytoplankton biomass. one of the major challenges in this approach lies in the assignment of the appropriate model parameters that define the photosynthetic response of phytoplankton to the light field. in the present study, a global database of in situ measurements of photosynthesis versus irradiance (p-i) parameters and a 20-year record of climate quality satellite observations were used to assess global primary production and its variability with seasons and locations as well as between years. in addition, the sensitivity of the computed primary production to potential changes in the photosynthetic response of phytoplankton cells under changing environmental conditions was investigated. global annual primary production varied from 48.7 to 52.5 gt c yr‑1 over the period of 1998–2018. inter-annual changes in global primary production did not follow a linear trend and regional differences in the magnitude and direction of change in primary production were observed. trends in primary production followed directly from changes in chlorophyll-a and were related to changes in the physico-chemical conditions of the water column due to inter-annual and multi-decadal climate oscillations. moreover, the sensitivity analysis in which p-i parameters were adjusted by ±1 standard deviation showed the importance of accurately assigning photosynthetic parameters in global and regional calculations of primary production. the assimilation number of the p-i curve showed strong relationships with environmental variables such as temperature and had a practically one-to-one relationship with the magnitude of change in primary production. in the future, such empirical relationships could potentially be used for a more dynamic assignment of photosynthetic rates in the estimation of global primary production. relationships between the initial slope of the p-i curve and environmental co-variables were more elusive. | primary production, an index of climate change in the ocean: satellite-based estimates over two decades |
i review the influence jets and the bubbles they inflate might have on their ambient gas as they operate through a negative jet feedback mechanism (jfm). i discuss astrophysical systems where jets are observed to influence the ambient gas, in many cases by inflating large, hot, and low-density bubbles, and systems where the operation of the jfm is still a theoretical suggestion. the first group includes cooling flows in galaxies and clusters of galaxies, star-forming galaxies, young stellar objects, and bipolar planetary nebulae. the second group includes core collapse supernovae, the common envelope evolution, the grazing envelope evolution, and intermediate luminosity optical transients. the suggestion that the jfm operates in these four types of systems is based on the assumption that jets are much more common than what is inferred from objects where they are directly observed. common to all eight types of systems reviewed here is the presence of a compact object inside an extended ambient gas. the ambient gas serves as a potential reservoir of mass to be accreted on to the compact object. if the compact object launches jets as it accretes mass, the jets might reduce the accretion rate as they deposit energy to the ambient gas, or even remove the entire ambient gas, hence closing a negative feedback cycle. | the jet feedback mechanism (jfm) in stars, galaxies and clusters |
we provide a calculation of pan-starrs’ ability to detect objects similar to the interstellar object 1i/2017 u1 (hereafter ‘oumuamua), including the most detectable approach vectors and the effect of object size on detection efficiency. using our updated detection cross section, we infer an interstellar number density of such objects ({n}is}≈ 0.2 {au}}-3). this translates to a mass density of {ρ }is}≈ 4 {m}\oplus{pc}}-3 that cannot be populated unless every star is contributing. we find that, given current models, such a number density cannot arise from the ejection of inner solar system material during planet formation. we note that a stellar system’s oort cloud will be released after a star’s main-sequence life time and may provide enough material to obtain the observed density. the challenge is that oort cloud bodies are icy and ‘oumuamua was observed to be dry, which necessitates a crust-generation mechanism. | interstellar interlopers: number density and origin of ‘oumuamua-like objects |
the hr 8799 system uniquely harbors four young super-jupiters whose orbits can provide insights into the system’s dynamical history and constrain the masses of the planets themselves. using the gemini planet imager, we obtained down to one milliarcsecond precision on the astrometry of these planets. we assessed four-planet orbit models with different levels of constraints and found that assuming the planets are near 1:2:4:8 period commensurabilities, or are coplanar, does not worsen the fit. we added the prior that the planets must have been stable for the age of the system (40 myr) by running orbit configurations from our posteriors through n-body simulations and varying the masses of the planets. we found that only assuming the planets are both coplanar and near 1:2:4:8 period commensurabilities produces dynamically stable orbits in large quantities. our posterior of stable coplanar orbits tightly constrains the planets’ orbits, and we discuss implications for the outermost planet b shaping the debris disk. a four-planet resonance lock is not necessary for stability up to now. however, planet pairs d and e, and c and d, are each likely locked in two-body resonances for stability if their component masses are above 6 m jup and 7 m jup, respectively. combining the dynamical and luminosity constraints on the masses using hot-start evolutionary models and a system age of 42 ± 5 myr, we found the mass of planet b to be 5.8 ± 0.5 m jup, and the masses of planets c, d, and e to be {7.2}-0.7+0.6 {m}jup} each. | dynamical constraints on the hr 8799 planets with gpi |
astronomical calculations reveal the solar system’s dynamical evolution, including its chaoticity, and represent the backbone of cyclostratigraphy and astrochronology. an absolute, fully calibrated astronomical time scale has hitherto been hampered beyond ~50 million years before the present (ma) because orbital calculations disagree before that age. here, we present geologic data and a new astronomical solution (zb18a) showing exceptional agreement from ~58 to 53 ma. we provide a new absolute astrochronology up to 58 ma and a new paleocene-eocene boundary age (56.01 ± 0.05 ma). we show that the paleocene-eocene thermal maximum (petm) onset occurred near a 405-thousand-year (kyr) eccentricity maximum, suggesting an orbital trigger. we also provide an independent petm duration (170 ± 30 kyr) from onset to recovery inflection. our astronomical solution requires a chaotic resonance transition at ~50 ma in the solar system’s fundamental frequencies. | solar system chaos and the paleocene-eocene boundary age constrained by geology and astronomy |
we present a velocimetric and spectropolarimetric analysis of 27 observations of the 22-myr m1 star au microscopii (au mic) collected with the high-resolution yjhk (0.98-2.35 μm) spectropolarimeter spirou from 2019 september 18 to november 14. our radial velocity (rv) time-series exhibits activity-induced fluctuations of 45 m s-1 rms, ∼3 times smaller than those measured in the optical domain, that we filter using gaussian process regression. we report a 3.9σ detection of the recently discovered 8.46 -d transiting planet au mic b, with an estimated mass of 17.1 $^{+4.7}_{-4.5}$ m⊕ and a bulk density of 1.3 ± 0.4 g cm-3, inducing an rv signature of semi-amplitude k = 8.5 $^{+2.3}_{-2.2}$ m s-1 in the spectrum of its host star. a consistent detection is independently obtained when we simultaneously image stellar surface inhomogeneities and estimate the planet parameters with zeeman-doppler imaging (zdi). using zdi, we invert the time-series of unpolarized and circularly polarized spectra into surface brightness and large-scale magnetic maps. we find a mainly poloidal and axisymmetric field of 475 g, featuring, in particular, a dipole of 450 g tilted at 19° to the rotation axis. moreover, we detect a strong differential rotation of dω = 0.167 ± 0.009 rad d-1 shearing the large-scale field, about twice stronger than that shearing the brightness distribution, suggesting that both observables probe different layers of the convective zone. even though we caution that more rv measurements are needed to accurately pin down the planet mass, au mic b already appears as a prime target for constraining planet formation models, studying the interactions with the surrounding debris disc, and characterizing its atmosphere with upcoming space- and ground-based missions. | investigating the young au mic system with spirou: large-scale stellar magnetic field and close-in planet mass |
planetary rings are observed not only around giant planets1, but also around small bodies such as the centaur chariklo2 and the dwarf planet haumea3. up to now, all known dense rings were located close enough to their parent bodies, being inside the roche limit, where tidal forces prevent material with reasonable densities from aggregating into a satellite. here we report observations of an inhomogeneous ring around the trans-neptunian body (50000) quaoar. this trans-neptunian object has an estimated radius4 of 555 km and possesses a roughly 80-km satellite5 (weywot) that orbits at 24 quaoar radii6,7. the detected ring orbits at 7.4 radii from the central body, which is well outside quaoar's classical roche limit, thus indicating that this limit does not always determine where ring material can survive. our local collisional simulations show that elastic collisions, based on laboratory experiments8, can maintain a ring far away from the body. moreover, quaoar's ring orbits close to the 1/3 spin-orbit resonance9 with quaoar, a property shared by chariklo's2,10,11 and haumea's3 rings, suggesting that this resonance plays a key role in ring confinement for small bodies. | a dense ring of the trans-neptunian object quaoar outside its roche limit |
we present the confirmation of two new planets transiting the nearby mid-m dwarf ltt 3780 (tic 36724087, toi-732, v = 13.07, ks = 8.204, rs = 0.374 r⊙, ms = 0.401 m⊙, d = 22 pc). the two planet candidates are identified in a single transiting exoplanet survey satellite sector and validated with reconnaissance spectroscopy, ground-based photometric follow-up, and high-resolution imaging. with measured orbital periods of pb = 0.77, pc = 12.25 days and sizes rp,b = 1.33 ± 0.07, rp,c = 2.30 ± 0.16 r⊕, the two planets span the radius valley in period-radius space around low-mass stars, thus making the system a laboratory to test competing theories of the emergence of the radius valley in that stellar mass regime. by combining 63 precise radial velocity measurements from the high accuracy radial velocity planet searcher (harps) and harps-n, we measure planet masses of ${m}_{p,b}={2.62}_{-0.46}^{+0.48}$ and ${m}_{p,c}={8.6}_{-1.3}^{+1.6}$ m⊕, which indicates that ltt 3780b has a bulk composition consistent with being earth-like, while ltt 3780c likely hosts an extended h/he envelope. we show that the recovered planetary masses are consistent with predictions from both photoevaporation and core-powered mass-loss models. the brightness and small size of ltt 3780, along with the measured planetary parameters, render ltt 3780b and c as accessible targets for atmospheric characterization of planets within the same planetary system and spanning the radius valley. | a pair of tess planets spanning the radius valley around the nearby mid-m dwarf ltt 3780 |
prestellar cores represent the initial conditions in the process of star and planet formation. their low temperatures (<10 k) allow the formation of thick icy dust mantles, which will be partially preserved in future protoplanetary disks, ultimately affecting the chemical composition of planetary systems. previous observations have shown that carbon- and oxygen-bearing species, in particular co, are heavily depleted in prestellar cores due to the efficient molecular freeze-out onto the surface of cold dust grains. however, n-bearing species such as nh3 and, in particular, its deuterated isotopologues appear to maintain high abundances where co molecules are mainly in the solid phase. thanks to alma, we present here the first clear observational evidence of nh2d freeze-out toward the l1544 prestellar core, suggestive of the presence of a "complete depletion zone" within a ≃1800 au radius, in agreement with astrochemical prestellar core model predictions. our state-of-the-art chemical model coupled with a non-lte radiative transfer code demonstrates that nh2d becomes mainly incorporated in icy mantles in the central 2000 au and starts freezing out already at ≃7000 au. radiative transfer effects within the prestellar core cause the nh2d(111 - 101) emission to appear centrally concentrated, with a flattened distribution within the central ≃3000 au, unlike the 1.3 mm dust continuum emission, which shows a clear peak within the central ≃1800 au. this prevented nh2d freeze-out from being detected in previous observations, where the central 1000 au cannot be spatially resolved. | the central 1000 au of a prestellar core revealed with alma. ii. almost complete freeze-out |
the so-called lidov-kozai oscillation is very well known and applied to various problems in solar system dynamics. this mechanism makes the orbital inclination and eccentricity of the perturbed body in the circular restricted three-body system oscillate with a large amplitude under certain conditions. it is widely accepted that the theoretical framework of this phenomenon was established independently in the early 1960s by a soviet union dynamicist (michail l'vovich lidov) and by a japanese celestial mechanist (yoshihide kozai). a large variety of studies has stemmed from the original works by lidov and kozai, now having the prefix of "lidov-kozai" or "kozai- lidov." however, from a survey of past literature published in late nineteenth to early twentieth century, we have confirmed that there already existed a pioneering work using a similar analysis of this subject established in that period. this was accomplished by a swedish astronomer, edvard hugo von zeipel. in this monograph, we first outline the basic framework of the circular restricted three-body problem including typical examples where the lidov-kozai oscillation occurs. then, we introduce what was discussed and learned along this line of studies from the early to mid-twentieth century by summarizing the major works of lidov, kozai, and relevant authors. finally, we make a summary of von zeipel's work, and show that his achievements in the early twentieth century already comprehended most of the fundamental and necessary formulations that the lidov-kozai oscillation requires. by comparing the works of lidov, kozai, and von zeipel, we assert that the prefix "von zeipel-lidov-kozai" should be used for designating this theoretical framework, and not just lidov-kozai or kozai-lidov. | the lidov-kozai oscillation and hugo von zeipel |
we highlight that the anomalous orbits of trans-neptunian objects (tnos) and an excess in microlensing events in the 5-year optical gravitational lensing experiment data set can be simultaneously explained by a new population of astrophysical bodies with mass several times that of the earth (m⊕). we take these objects to be primordial black holes (pbhs) and point out the orbits of tnos would be altered if one of these pbhs was captured by the solar system, inline with the planet 9 hypothesis. capture of a free floating planet is a leading explanation for the origin of planet 9, and we show that the probability of capturing a pbh instead is comparable. the observational constraints on a pbh in the outer solar system significantly differ from the case of a new ninth planet. this scenario could be confirmed through annihilation signals from the dark matter microhalo around the pbh. | what if planet 9 is a primordial black hole? |
we review the origin and evolution of the atmospheres of earth, venus and mars from the time when their accreting bodies were released from the protoplanetary disk a few million years after the origin of the sun. if the accreting planetary cores reached masses ≥ 0.5 m_earth before the gas in the disk disappeared, primordial atmospheres consisting mainly of h_2 form around the young planetary body, contrary to late-stage planet formation, where terrestrial planets accrete material after the nebula phase of the disk. the differences between these two scenarios are explored by investigating non-radiogenic atmospheric noble gas isotope anomalies observed on the three terrestrial planets. the role of the young sun's more efficient euv radiation and of the plasma environment into the escape of early atmospheres is also addressed. we discuss the catastrophic outgassing of volatiles and the formation and cooling of steam atmospheres after the solidification of magma oceans and we describe the geochemical evidence for additional delivery of volatile-rich chondritic materials during the main stages of terrestrial planet formation. the evolution scenario of early earth is then compared with the atmospheric evolution of planets where no active plate tectonics emerged like on venus and mars. we look at the diversity between early earth, venus and mars, which is found to be related to their differing geochemical, geodynamical and geophysical conditions, including plate tectonics, crust and mantle oxidation processes and their involvement in degassing processes of secondary n_2 atmospheres. the buildup of atmospheric n_2, o_2, and the role of greenhouse gases such as co_2 and ch_4 to counter the faint young sun paradox (fysp), when the earliest life forms on earth originated until the great oxidation event ≈ 2.3 gyr ago, are addressed. this review concludes with a discussion on the implications of understanding earth's geophysical and related atmospheric evolution in relation to the discovery of potential habitable terrestrial exoplanets. | origin and evolution of the atmospheres of early venus, earth and mars |
martian moons exploration, mmx, is the new sample return mission planned by the japan aerospace exploration agency (jaxa) targeting the two martian moons with the scheduled launch in 2024 and return to the earth in 2029. the major scientific objectives of this mission are to determine the origin of phobos and deimos, to elucidate the early solar system evolution in terms of volatile delivery across the snow line to the terrestrial planets having habitable surface environments, and to explore the evolutionary processes of both moons and mars surface environment. to achieve these objectives, during a stay in circum-martian space over about 3 years mmx will collect samples from phobos along with close-up observations of this inner moon and carry out multiple flybys of deimos to make comparative observations of this outer moon. simultaneously, successive observations of the martian atmosphere will also be made by utilizing the advantage of quasi-equatorial spacecraft orbits along the moons' orbits. | martian moons exploration mmx: sample return mission to phobos elucidating formation processes of habitable planets |
about half of all optical observations collected via spaceborne satellites are affected by haze or clouds. consequently, cloud coverage affects the remote sensing practitioner's capabilities of a continuous and seamless monitoring of our planet. this work addresses the challenge of optical satellite image reconstruction and cloud removal by proposing a novel multi-modal and multi-temporal data set called sen12ms-cr-ts. we propose two models highlighting the benefits and use cases of sen12ms-cr-ts: first, a multi-modal multi-temporal 3d-convolution neural network that predicts a cloud-free image from a sequence of cloudy optical and radar images. second, a sequence-to-sequence translation model that predicts a cloud-free time series from a cloud-covered time series. both approaches are evaluated experimentally, with their respective models trained and tested on sen12ms-cr-ts. the conducted experiments highlight the contribution of our data set to the remote sensing community as well as the benefits of multi-modal and multi-temporal information to reconstruct noisy information. our data set is available at https://patricktum.github.io/cloud_removal | sen12ms-cr-ts: a remote-sensing data set for multimodal multitemporal cloud removal |
our planet is changing at paces never observed before. species extinction is happening at faster rates than ever, greatly exceeding the five mass extinctions in the fossil record. nevertheless, our lives are strongly based on services provided by ecosystems, thus the responses to global change of our natural heritage are of immediate concern. understanding the relationship between complexity and stability of ecosystems is of key importance for the maintenance of the balance of human growth and the conservation of all the natural services that ecosystems provide. mathematical network models can be used to simplify the vast complexity of the real world, to formally describe and investigate ecological phenomena, and to understand ecosystems propensity of returning to its functioning regime after a stress or a perturbation. the use of ecological‑network models to study the relationship between complexity and stability of natural ecosystems is the focus of this review. the concept of ecological networks and their characteristics are first introduced, followed by central and occasionally contrasting definitions of complexity and stability. the literature on the relationship between complexity and stability in different types of models and in real ecosystems is then reviewed, highlighting the theoretical debate and the lack of consensual agreement. the summary of the importance of this line of research for the successful management and conservation of biodiversity and ecosystem services concludes the review. | complexity and stability of ecological networks: a review of the theory |
the extensive array of mid-20th century stratigraphic event signals associated with the 'great acceleration' enables precise and unambiguous recognition of the anthropocene as an epoch/series within the geological time scale. a mid-20th century inception is consistent with earth system science analysis in which the anthropocene term and concept arose, and would reflect the reality that our planet has sharply exited the range of natural variability characterizing the holocene epoch/series, which the anthropocene would therefore terminate. an alternative, recently proposed 'geological event' approach to the anthropocene is primarily an interdisciplinary concept, encompassing historical and socio-cultural processes and their global environmental impacts over a diachronous timeframe that extends back at least many millennia. resembling more closely a geological episode than an event, it would decouple the anthropocene from its chronostratigraphic delineation and association with an abrupt planetary perturbation; but separately defined and differently named it might be usefully complementary. we recommend a clear separation of epochs, events and episodes. an epoch is a formal subdivision of the geological time scale, and its correlation may be assisted by one or more events; an event is usually, and particularly in the quaternary, a brief incident or perturbation with a sedimentary expression; and an episode is a longer, internally complex time interval that may include several events and even extend across several epochs. | the proposed anthropocene epoch/series is underpinned by an extensive array of mid-20 th century stratigraphic event signals |
mars’ sedimentary rock record preserves information on geological (and potential astrobiological) processes that occurred on the planet billions of years ago. the curiosity rover is exploring the lower reaches of mount sharp, in gale crater on mars. a traverse from vera rubin ridge to glen torridon has allowed curiosity to examine a lateral transect of rock strata laid down in a martian lake ~3.5 billion years ago. we report spatial differences in the mineralogy of time-equivalent sedimentary rocks <400 meters apart. these differences indicate localized infiltration of silica-poor brines, generated during deposition of overlying magnesium sulfate-bearing strata. we propose that destabilization of silicate minerals driven by silica-poor brines (rarely observed on earth) was widespread on ancient mars, because sulfate deposits are globally distributed. | brine-driven destruction of clay minerals in gale crater, mars |
methane-producing microorganisms are thought to be among the earliest cellular life forms colonizing our planet, and are major contributors to the past and present global carbon cycle. currently, all methanogens belong to the archaeal domain of life, and there is compounding evidence for a variety of methanogenic metabolisms among a wide distribution of archaeal phyla. however, the predominantly hydrogenotrophic (co2-fixing) euryarchaeota are distinct from the recently discovered methylotrophic (biomass-degrading) noneuryarchaea, making the shared ancestry and origins of all methanogens unclear. we discovered hydrogenotrophic methanogenesis in a thermophilic order of the verstraetearchaeota, a noneuryarchaeote. the verstraetearchaeota, hitherto known as methylotrophs, unify the origins of methanogenesis and shed light on how organisms can evolve to adapt from hydrogenotrophic to methylotrophic methane metabolism. | hydrogenotrophic methanogenesis in archaeal phylum verstraetearchaeota reveals the shared ancestry of all methanogens |
accurate land use land cover (lulc) classification is vital for the sustainable management of natural resources and to learn how the landscape is changing due to climate. for accurate and efficient lulc classification, high-quality datasets and robust classification methods are required. with the increasing availability of satellite data, geospatial analysis tools, and classification methods, it is essential to systematically assess the performance of different combinations of satellite data and classification methods to help select the best approach for lulc classification. therefore, this study aims to evaluate the lulc classification performance of two commonly used platforms (i.e., arcgis pro and google earth engine) with different satellite datasets (i.e., landsat, sentinel, and planet) through a case study for the city of charlottetown in canada. specifically, three classifiers in arcgis pro, including support vector machine (svm), maximum likelihood (ml), and random forest/random tree (rf/rt), are utilized to develop lulc maps over the period of 2017-2021. whereas four classifiers in google earth engine, including svm, rf/rt, minimum distance (md), and classification and regression tree (cart), are used to develop lulc maps for the same period. to identify the most efficient and accurate classifier, the overall accuracy and kappa coefficient for each classifier is calculated throughout the study period for all combinations of satellite data, classification platforms, and methods. change detection is then conducted using the best classifier to quantify the lulc changes over the study period. results show that the svm classifier in both arcgis pro and google earth engine presents the best performance compared to other classifiers. in particular, the svm in arcgis pro shows an overall accuracy of 89% with landsat, 91% with sentinel, and 94% with planet. similarly, in google earth engine, the svm shows an accuracy of 87% with landsat 8 and 92% with sentinel 2. furthermore, change detection results show that 13.80% and 14.10% of forest areas have been turned into bare land and urban class, respectively, and 3.90% of the land has been converted into the urban area from 2017 to 2021, suggesting the intensive urbanization. the results of this study will provide the scientific basis for selecting the remote sensing classifier and satellite imagery to develop accurate lulc maps. | comparison of land use land cover classifiers using different satellite imagery and machine learning techniques |
we present a statistical analysis of the kepler m dwarf planet hosts, with a particular focus on the fractional number of systems hosting multiple transiting planets. we manufacture synthetic planetary systems within a range of planet multiplicity and mutual inclination for comparison to the kepler yield. similarly to studies of kepler exoplanetary systems around more massive stars, we report that the number of singly transiting planets found by kepler is too high to be consistent with a single population of multi-planet systems, a finding that cannot be attributed to selection biases. to account for the excess singleton planetary systems we adopt a mixture model and find that 53 ± 10% of planetary systems are either single or contain multiple planets with large mutual inclinations. the other 47 ± 10% of systems contain {7.5}-1.5+0.5 planets with mutual inclinations of 2.°0 ± 1.°3. this mutual inclination range is consistent with studies of transit durations within multiply transiting systems. the mixture model is preferred 8:1 to a model with only one architecture. thus, we find that the so-called “kepler dichotomy” holds for planets orbiting m dwarfs as well as sun-like stars. | the kepler dichotomy among the m dwarfs: half of systems contain five or more coplanar planets |
current models of (exo)planet formation often rely on a large influx of so-called “pebbles” from the outer disk into the planet formation region. in this paper, we investigate how the formation/coagulation of pebbles in the cold outer regions of protoplanetary disks and their subsequent migration to the inner disk can alter the gas-phase co distribution both interior and exterior to the midplane co snowline. by simulating the resulting co abundances in the midplane as well as the warm surface layer, we identify observable signatures of large-scale pebble formation and migration that can be used as “smoking guns” for this important process. specifically, we find that after 1 myr, the formation and settling of icy pebbles results in the removal of up to 80% of the co vapor in the warm (t> 22 {{k}}) disk layers outside the co snowline, while the radial migration of pebbles results in the generation of a plume of co vapor inside the snowline, increasing the co abundance by a factor ∼2-6 depending on the strength of the turbulence and the sizes of the individual pebbles. the absence of this plume of co vapor in young nearby disks could indicate efficient conversion of co into a more refractory species, or to the radial mass flux of pebbles being drastically reduced by, for example, disk inhomogeneities or early planetesimal formation. | transport of co in protoplanetary disks: consequences of pebble formation, settling, and radial drift |
we present microlensing events in the 2015 korea microlensing telescope network (kmtnet) data and our procedure for identifying these events. in particular, candidates were detected with a novel “completed-event” microlensing event-finder algorithm. the algorithm works by making linear fits to a ({t}0,{t}{eff},{u}0) grid of point-lens microlensing models. this approach is rendered computationally efficient by restricting u 0 to just two values (0 and 1), which we show is quite adequate. the implementation presented here is specifically tailored to the commission-year character of the 2015 data, but the algorithm is quite general and has already been applied to a completely different (non-kmtnet) data set. we outline expected improvements for 2016 and future kmtnet data. the light curves of the 660 “clear microlensing” and 182 “possible microlensing” events that were found in 2015 are presented along with our policy for their public release. | korea microlensing telescope network microlensing events from 2015: event-finding algorithm, vetting, and photometry |
many dynamical aspects of the solar system can be explained by the outer planets experiencing a period of orbital instability sometimes called the nice model. though often correlated with a perceived delayed spike in the lunar cratering record known as the late heavy bombardment (lhb), recent work suggests that this event may have occurred much earlier; perhaps during the epoch of terrestrial planet formation. while current simulations of terrestrial accretion can reproduce many observed qualities of the solar system, replicating the small mass of mars requires modification to standard planet formation models. here we use 800 dynamical simulations to show that an early instability in the outer solar system strongly influences terrestrial planet formation and regularly yields properly sized mars analogs. our most successful outcomes occur when the terrestrial planets evolve an additional 1-10 million years (myr) following the dispersal of the gas disk, before the onset of the giant planet instability. in these simulations, accretion has begun in the mars region before the instability, but the dynamical perturbation induced by the giant planets' scattering removes large embryos from mars' vicinity. large embryos are either ejected or scattered inward toward earth and venus (in some cases to deliver water), and mars is left behind as a stranded embryo. an early giant planet instability can thus replicate both the inner and outer solar system in a single model. | mars' growth stunted by an early giant planet instability |
carmenes is a spectrograph for radial velocity surveys of m dwarfs with the aim of detecting earth-mass planets orbiting in the habitable zones of their host stars. to ensure an optimal use of the carmenes guaranteed time observations, in this paper we investigate the correlation of activity and rotation for approximately 2200 m dwarfs, ranging in spectral type from m0.0 v to m9.0 v. we present new high-resolution spectroscopic observations with feros, cafe, and hrs of approximately 500 m dwarfs. for each new observation, we determined its radial velocity and measured its hα activity index and its rotation velocity. additionally, we have multiple observations of many stars to investigate if there are any radial velocity variations due to multiplicity. the results of our survey confirm that early-m dwarfs are hα inactive with low rotational velocities and that late-m dwarfs are hα active with very high rotational velocities. the results of this high-resolution analysis comprise the most extensive catalogue of rotation and activity in m dwarfs currently available. based on observations made at the calar alto observatory, spain, the european southern observatory, la silla, chile and mcdonald observatory, usa.tables a.1-a.3 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/614/a76 | carmenes input catalogue of m dwarfs. iii. rotation and activity from high-resolution spectroscopic observations |
most planets currently amenable to transit spectroscopy are close enough to their host stars to exhibit a relatively strong day to night temperature gradient. for hot planets this leads to a chemical composition dichotomy between the two hemispheres. in the extreme case of ultra-hot jupiters, some species, such as molecular hydrogen and water, are strongly dissociated on the day side while others, such as carbon monoxide, are not. however, most current retrieval algorithms rely on 1d forward models that are unable to reproduce this effect. we thus investigate how the 3d structure of the atmosphere biases the abundances retrieved using commonly used algorithms. we study the case of wasp-121b as a prototypical ultra-hot jupiter. we use the simulations of this planet performed with the substellar and planetary atmospheric radiation and circulation global climate model and generate transmission spectra that fully account for the 3d structure of the atmosphere with pytmosph3r. these spectra are then analyzed using the taurex retrieval code. we find that the ultra-hot jupiter transmission spectra exhibit muted h2o features that originate on the night side where the temperature, hence the scale-height, is smaller than on the day side. however, the spectral features of molecules present on the day side are boosted by both its high temperature and low mean molecular weight. as a result, the retrieved parameters are strongly biased compared to the ground truth. in particular the [co]/[h2o] is overestimated by one to three orders of magnitude. this must be kept in mind when using the retrieval analysis to infer the c/o of a planet's atmosphere. we also discuss whether indicators can allow us to infer the 3d structure of an observed atmosphere. finally, we show that wide field camera 3 from hubble space telescope transmission data of wasp-121b are compatible with the day-night thermal and compositional dichotomy predicted by models. | strong biases in retrieved atmospheric composition caused by day-night chemical heterogeneities |
recently, we introduced planetary atmospheric tool for observer noobs (platon), a python package that calculates model transmission spectra for exoplanets and retrieves atmospheric characteristics based on observed spectra. we now expand its capabilities to include the ability to compute secondary eclipse depths. we have also added the option to calculate models using the correlated-k method for radiative transfer, which improves accuracy without sacrificing speed. additionally, we update the opacities in platon—many of which were generated using old or proprietary line lists—using the most recent and complete public line lists. these opacities are made available at r = 1000 and r = 10,000 over the 0.3-30 μm range, and at r = 375,000 in select near-ir bands, making it possible to utilize platon for ground-based high-resolution cross-correlation studies. to demonstrate platon's new capabilities, we perform a retrieval on published hubble space telescope (hst) and spitzer transmission and emission spectra of the archetypal hot jupiter hd 189733b. this is the first joint transit and secondary eclipse retrieval for this planet in the literature, as well as the most comprehensive set of both transit and eclipse data assembled for a retrieval to date. we find that these high signal-to-noise data are well matched by atmosphere models with a c/o ratio of ${0.66}_{-0.09}^{+0.05}$ and a metallicity of ${12}_{-5}^{+8}$ times solar where the terminator is dominated by extended nanometer-sized haze particles at optical wavelengths. these are among the smallest uncertainties reported to date for an exoplanet, demonstrating both the power and the limitations of hst and spitzer exoplanet observations. | platon ii: new capabilities and a comprehensive retrieval on hd 189733b transit and eclipse data |
we present robust planet occurrence rates for kepler planet candidates around m stars for planet radii rp = 0.5-4 r⊕ and orbital periods p = 0.5-256 d using the approximate bayesian computation technique. this work incorporates the final kepler dr25 planet candidate catalogue and data products and augments them with updated stellar properties using gaia dr2 and 2mass point source catalogue. we apply a set of selection criteria to select a sample of 1746 kepler m dwarf targets that host 89 associated planet candidates. these early-type m dwarfs and late k dwarfs were selected from cross-referenced targets using several photometric quality flags from gaia dr2 and colour-magnitude cuts using 2mass magnitudes. we estimate a habitable zone occurrence rate of $f_{\textrm {m,hz}} = 0.33^{+0.10}_{-0.12}$ for planets with 0.75-1.5 r⊕ size. we caution that occurrence rate estimates for kepler m stars are sensitive to the choice of prior due to the small sample of target stars and planet candidates. for example, we find an occurrence rate of $4.2^{+0.6}_{-0.6}$ or $8.4^{+1.2}_{-1.1}$ planets per m dwarf (integrating over rp = 0.5-4 r⊕ and p = 0.5-256 d) for our two choices of prior. these occurrence rates are greater than those for fgk dwarf target when compared at the same range of orbital periods, but similar to occurrence rates when computed as a function of equivalent stellar insolation. combining our result with recent studies of exoplanet architectures indicates that most, and potentially all, early-type m dwarfs harbour planetary systems. | occurrence rates of planets orbiting m stars: applying abc to kepler dr25, gaia dr2, and 2mass data |
context. in recent decades, direct imaging has confirmed the existence of substellar companions (exoplanets or brown dwarfs) on wide orbits (>10 au) around their host stars. in striving to understand their formation and evolution mechanisms, in 2015 we initiated the sphere infrared survey for exoplanets (shine), a systematic direct imaging survey of young, nearby stars that is targeted at exploring their demographics.aims: we aim to detect and characterize the population of giant planets and brown dwarfs beyond the snow line around young, nearby stars. combined with the survey completeness, our observations offer the opportunity to constrain the statistical properties (occurrence, mass and orbital distributions, dependency on the stellar mass) of these young giant planets.methods: in this study, we present the observing and data analysis strategy, the ranking process of the detected candidates, and the survey performances for a subsample of 150 stars that are representative of the full shine sample. observations were conducted in a homogeneous way between february 2015 and february 2017 with the dedicated ground-based vlt/sphere instrument equipped with the ifs integral field spectrograph and the irdis dual-band imager, covering a spectral range between 0.9 and 2.3 μm. we used coronographic, angular, and spectral differential imaging techniques to achieve the best detection performances for this study, down to the planetary mass regime.results: we processed, in a uniform manner, more than 300 shine observations and datasets to assess the survey typical sensitivity as a function of the host star and of the observing conditions. the median detection performance reached 5σ-contrasts of 13 mag at 200 mas and 14.2 mag at 800 mas with the ifs (yj and yjh bands), and of 11.8 mag at 200 mas, 13.1 mag at 800 mas, and 15.8 mag at 3 as with irdis in h band, delivering one of the deepest sensitivity surveys thus far for young, nearby stars. a total of sixteen substellar companions were imaged in this first part of shine: seven brown dwarf companions and ten planetary-mass companions.these include two new discoveries, hip 65426 b and hip 64892 b, but not the planets around pds70 that had not been originally selected for the shine core sample. a total of 1483 candidates were detected, mainly in the large field of view that characterizes irdis. the color-magnitude diagrams, low-resolution spectrum (when available with ifs), and follow-up observations enabled us to identify the nature (background contaminant or comoving companion) of about 86% of our subsample. the remaining cases are often connected to crowded-field follow-up observations that were missing. finally, even though shine was not initially designed for disk searches, we imaged twelve circumstellar disks, including three new detections around the hip 73145, hip 86598, and hd 106906 systems.conclusions: nowadays, direct imaging provides a unique opportunity to probe the outer part of exoplanetary systems beyond 10 au to explore planetary architectures, as highlighted by the discoveries of: one new exoplanet, one new brown dwarf companion, and three new debris disks during this early phase of shine. it also offers the opportunity to explore and revisit the physical and orbital properties of these young, giant planets and brown dwarf companions (relative position, photometry, and low-resolution spectrum in near-infrared, predicted masses, and contrast in order to search for additional companions). finally, these results highlight the importance of finalizing the shine systematic observation of about 500 young, nearby stars for a full exploration of their outer part to explore the demographics of young giant planets beyond 10 au and to identify the most interesting systems for the next generation of high-contrast imagers on very large and extremely large telescopes. full table a.1 is 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/a71 | the sphere infrared survey for exoplanets (shine). ii. observations, data reduction and analysis, detection performances, and initial results |
thermal convection is the dominant mechanism of energy transport in the outer envelope of the sun (one-third by radius). it drives global fluid circulations and magnetic fields observed on the solar surface. vigorous surface convection excites a broadband spectrum of acoustic waves that propagate within the interior and set up modal resonances. these acoustic waves, also called seismic waves in this context, are observed at the surface of the sun by space- and ground-based telescopes. seismic sounding, the study of these seismic waves to infer the internal properties of the sun, constitutes helioseismology. here we review our knowledge of solar convection, especially that obtained through seismic inference. several characteristics of solar convection, such as differential rotation, anisotropic reynolds stresses, the influence of rotation on convection, and supergranulation, are considered. on larger scales, several inferences suggest that convective velocities are substantially smaller than those predicted by theory and simulations. this discrepancy challenges the models of internal differential rotation that rely on convective stresses as a driving mechanism and provide an important benchmark for numerical simulations. | seismic sounding of convection in the sun |
high-resolution optical spectroscopy is a powerful tool to characterise exoplanetary atmospheres from the ground. the sodium d lines, with their large cross sections, are especially suited to studying the upper layers of atmospheres in this context. we report on the results from hot exoplanet atmosphere resolved with transit spectroscopy survey (hearts), a spectroscopic survey of exoplanet atmospheres, performing a comparative study of hot gas giants to determine the effects of stellar irradiation. in this second installation of the series, we highlight the detection of neutral sodium on the ultra-hot giant wasp-76b. we observed three transits of the planet using the high-accuracy radial-velocity planet searcher (harps) high-resolution spectrograph at the european southern observatory (eso) 3.6 m telescope and collected 175 spectra of wasp-76. we repeatedly detect the absorption signature of neutral sodium in the planet atmosphere (0.371 ± 0.034%; 10.75σ in a 0.75 å passband). the sodium lines have a gaussian profile with full width at half maximum (fwhm) of 27.6 ± 2.8 km s-1. this is significantly broader than the line spread function of harps (2.7 km s-1). we surmise that the observed broadening could trace the super-rotation in the upper atmosphere of this ultra-hot gas giant. based on observations made at eso 3.6 m telescope (la silla, chile) under eso programmes 090.c-0540 and 100.c-0750. | hot exoplanet atmospheres resolved with transit spectroscopy (hearts). ii. a broadened sodium feature on the ultra-hot giant wasp-76b |
small organic molecules, such as c2h, hcn, and h2co, are tracers of the c, n, and o budget in protoplanetary disks. we present high-angular-resolution (10-50 au) observations of c2h, hcn, and h2co lines in five protoplanetary disks from the molecules with alma at planet-forming scales (maps) alma large program. we derive column density and excitation temperature profiles for hcn and c2h, and find that the hcn emission arises in a temperate (20-30 k) layer in the disk, while c2h is present in relatively warmer (20-60 k) layers. in the case of hd 163296, we find a decrease in column density for hcn and c2h inside one of the dust gaps near ~83 au, where a planet has been proposed to be located. we derive h2co column density profiles assuming temperatures between 20 and 50 k, and find slightly higher column densities in the colder disks around t tauri stars than around herbig ae stars. the h2co column densities rise near the location of the co snowline and/or millimeter dust edge, suggesting an efficient release of h2co ices in the outer disk. finally, we find that the inner 50 au of these disks are rich in organic species, with abundances relative to water that are similar to cometary values. comets could therefore deliver water and key organics to future planets in these disks, similar to what might have happened here on earth. this paper is part of the maps special issue of the astrophysical journal supplement. | molecules with alma at planet-forming scales (maps). vi. distribution of the small organics hcn, c2h, and h2co |
a new class of exoplanets is beginning to emerge: planets with dayside atmospheres that resemble stellar atmospheres as most of their molecular constituents dissociate. the effects of the dissociation of these species will be varied and must be carefully accounted for. here we take the first steps toward understanding the consequences of dissociation and recombination of molecular hydrogen (h2) on atmospheric heat recirculation. using a simple energy balance model with eastward winds, we demonstrate that h2 dissociation/recombination can significantly increase the day-night heat transport on ultra-hot jupiters (uhjs): gas giant exoplanets where significant h2 dissociation occurs. the atomic hydrogen from the highly irradiated daysides of uhjs will transport some of the energy deposited on the dayside toward the nightside of the planet where the h atoms recombine into h2; this mechanism bears similarities to latent heat. given a fixed wind speed, this will act to increase the heat recirculation efficiency; alternatively, a measured heat recirculation efficiency will require slower wind speeds after accounting for h2 dissociation/recombination. | increased heat transport in ultra-hot jupiter atmospheres through h2 dissociation and recombination |
sub-neptune-sized exoplanets represent the most common types of planets in the milky way, yet many of their properties are unknown. here, we present a prescription to adapt the capabilities of the stellar evolution toolkit modules for experiments in stellar astrophysics to model sub-neptune-mass planets with h/he envelopes. with the addition of routines treating the planet core luminosity, heavy-element enrichment, atmospheric boundary condition, and mass-loss due to hydrodynamic winds, the evolutionary pathways of planets with diverse starting conditions are more accurately constrained. using these dynamical models, we construct mass-composition relationships of planets from 1-400 m ⊕ and investigate how mass-loss impacts their composition and evolution history. we demonstrate that planet radii are typically insensitive to the evolution pathway that brought the planet to its instantaneous mass, composition and age, with variations from hysteresis ≲ 2 % . we find that planet envelope mass-loss timescales, {τ }{env}, vary non-monotonically with h/he envelope mass fractions (at fixed planet mass). in our simulations of young (100 myr) low-mass ({m}{{p}}≲ 10 {m}\oplus ) planets with rocky cores, {τ }{env} is maximized at {m}{env}/{m}{{p}}=1 % to 3%. the resulting convergent mass-loss evolution could potentially imprint itself on the close-in planet population as a preferred h/he mass fraction of ∼ 1 % . looking ahead, we anticipate that this numerical code will see widespread applications complementing both 3d models and observational exoplanet surveys. | evolutionary analysis of gaseous sub-neptune-mass planets with mesa |
magma oceans were once ubiquitous in the early solar system, setting up the initial conditions for different evolutionary paths of planetary bodies. in particular, the redox conditions of magma oceans may have profound influence on the redox state of subsequently formed mantles and the overlying atmospheres. the relevant redox buffering reactions, however, remain poorly constrained. using first-principles simulations combined with thermodynamic modeling, we show that magma oceans of earth, mars, and the moon are likely characterized with a vertical gradient in oxygen fugacity with deeper magma oceans invoking more oxidizing surface conditions. this redox zonation may be the major cause for the earth's upper mantle being more oxidized than mars' and the moon's. these contrasting redox profiles also suggest that earth's early atmosphere was dominated by co2 and h2o, in contrast to those enriched in h2o and h2 for mars, and h2 and co for the moon. | a magma ocean origin to divergent redox evolutions of rocky planetary bodies and early atmospheres |
meeting the increasing global demand for agricultural products without depleting the limited resources of the planet is a major challenge that humanity is facing. most studies on global food security do not make projections past the year 2050, just as climate change and increasing demand for food are expected to intensify. moreover, past studies do not account for the water sustainability limits of irrigation expansion to presently rainfed areas. here we perform an integrated assessment that considers a range of factors affecting future food production and demand throughout the 21st century. we evaluate the self-sufficiency of 165 countries under sustainability, middle-of-the-road, and business-as-usual scenarios considering changes in diet, population, agricultural intensification, and climate. we find that under both the middle-of-the-road and business-as-usual trajectories global food self-sufficiency is likely to decline despite increased food production through sustainable agricultural intensification since projected food demand exceeds potential production. contrarily, under a sustainability scenario, we estimate that there will be enough food production to feed the global population. however, most countries in africa and the middle east will continue to be heavily reliant on imports throughout the 21st century under all scenarios. these results highlight future hotspots of crop production deficits, reliance on food imports, and vulnerability to food supply shocks. | global food self-sufficiency in the 21st century under sustainable intensification of agriculture |
comets are thought to preserve almost pristine dust particles, thus providing a unique sample of the properties of the early solar nebula. the microscopic properties of this dust played a key part in particle aggregation during the formation of the solar system. cometary dust was previously considered to comprise irregular, fluffy agglomerates on the basis of interpretations of remote observations in the visible and infrared and the study of chondritic porous interplanetary dust particles that were thought, but not proved, to originate in comets. although the dust returned by an earlier mission has provided detailed mineralogy of particles from comet 81p/wild, the fine-grained aggregate component was strongly modified during collection. here we report in situ measurements of dust particles at comet 67p/churyumov-gerasimenko. the particles are aggregates of smaller, elongated grains, with structures at distinct sizes indicating hierarchical aggregation. topographic images of selected dust particles with sizes of one micrometre to a few tens of micrometres show a variety of morphologies, including compact single grains and large porous aggregate particles, similar to chondritic porous interplanetary dust particles. the measured grain elongations are similar to the value inferred for interstellar dust and support the idea that such grains could represent a fraction of the building blocks of comets. in the subsequent growth phase, hierarchical agglomeration could be a dominant process and would produce aggregates that stick more easily at higher masses and velocities than homogeneous dust particles. the presence of hierarchical dust aggregates in the near-surface of the nucleus of comet 67p also provides a mechanism for lowering the tensile strength of the dust layer and aiding dust release. | aggregate dust particles at comet 67p/churyumov-gerasimenko |
we provide a brief review of many aspects of the planetary physics of hot jupiters. our aim is to cover most of the major areas of current study while providing the reader with additional references for more detailed follow up. we first discuss giant planet formation and subsequent orbital evolution via disk driven torques or dynamical interactions. more than one formation pathway is needed to understand the population. next, we examine our current understanding of the evolutionary history and current interior structure of the planets, where we focus on bulk composition as well as viable models to explain the inflated radii of the population. finally, we discuss aspects of their atmospheres in the context of observations and 1d and 3d models, including atmospheric structure and escape, spectroscopic signatures, and complex atmospheric circulation. the major opacity sources in these atmospheres, including alkali metals, water vapor, and others, are discussed. we discuss physics that control the 3d atmospheric circulation and day to night temperature structures. we conclude by suggesting important future work for still open questions. | hot jupiters: origins, structure, atmospheres |
context. dozens of protoplanetary disks have been imaged in scattered light during the last decade.aims: the variety of brightness, extension, and morphology from this census motivates a taxonomical study of protoplanetary disks in polarimetric light to constrain their evolution and establish the current framework of this type of observation.methods: we classified 58 disks with available polarimetric observations into six major categories (ring, spiral, giant, rim, faint, and small disks) based on their appearance in scattered light. we re-calculated the stellar and disk properties from the newly available gaia dr2 and related these properties with the disk categories.results: more than half of our sample shows disk substructures. for the remaining sources, the absence of detected features is due to their faintness, their small size, or the disk geometry. faint disks are typically found around young stars and typically host no cavity. there is a possible dichotomy in the near-infrared (nir) excess of sources with spiral-disks (high) and ring-disks (low). like spirals, shadows are associated with a high nir excess. if we account for the pre-main sequence evolutionary timescale of stars with different mass, spiral arms are likely associated with old disks. we also found a loose, shallow declining trend for the disk dust mass with time.conclusions: protoplanetary disks may form substructures like rings very early in their evolution but their detectability in scattered light is limited to relatively old sources ( ≳5 myr) where the recurrently detected disk cavities cause the outer disk to be illuminate. the shallow decrease of disk mass with time might be due to a selection effect, where disks observed thus far in scattered light are typically massive, bright transition disks with longer lifetimes than most disks. our study points toward spirals and shadows being generated by planets of a fraction of a jupiter mass to a few jupiter masses in size that leave their (observed) imprint on both the inner disk near the star and the outer disk cavity. | evolution of protoplanetary disks from their taxonomy in scattered light: spirals, rings, cavities, and shadows |
the angular momentum deficit (amd) of a planetary system is a measure of its orbital excitation and a predictor of long-term stability. we adopt the amd-stability criterion to constrain the orbital architectures for exoplanetary systems. previously, he et al. showed through forward modeling (syssim) that the observed multiplicity distribution can be well reproduced by two populations consisting of a low and a high mutual inclination component. here, we show that a broad distribution of mutual inclinations arising from systems at the amd-stability limit can also match the observed kepler population. we show that distributing a planetary system's maximum amd among its planets results in a multiplicity-dependent distribution of eccentricities and mutual inclinations. systems with intrinsically more planets have lower median eccentricities and mutual inclinations, and this trend is well described by power-law functions of the intrinsic planet multiplicity (n): ${\tilde{\mu }}_{e,n}\propto {n}^{-{1.74}_{-0.07}^{+0.11}}$ and ${\tilde{\mu }}_{i,n}\propto {n}^{-{1.73}_{-0.08}^{+0.09}}$ , where ${\tilde{\mu }}_{e,n}$ and ${\tilde{\mu }}_{i,n}$ are the medians of the eccentricity and inclination distributions. we also find that intrinsic single planets have higher eccentricities (σe,1 ∼ 0.25) than multiplanet systems and that the trends with multiplicity appear in the observed distributions of period-normalized transit duration ratios. we show that the observed preferences for planet-size orderings and uniform spacings are more extreme than what can be produced by the detection biases of the kepler mission alone. finally, we find that for systems with detected transiting planets between 5 and 10 days, there is another planet with a greater radial velocity signal ≃53% of the time. | architectures of exoplanetary systems. iii. eccentricity and mutual inclination distributions of amd-stable planetary systems |
exploiting the kepler transit data, we uncover a dramatic distinction in the prevalence of sub-jovian companions between systems that contain hot jupiters (hjs) (periods inward of 10 days) and those that host warm jupiters (wjs) (periods between 10 and 200 days). hjs, with the singular exception of wasp-47b, do not have any detectable inner or outer planetary companions (with periods inward of 50 days and sizes down to 2 r earth). restricting ourselves to inner companions, our limits reach down to 1 r earth. in stark contrast, half of the wjs are closely flanked by small companions. statistically, the companion fractions for hot and wjs are mutually exclusive, particularly in regard to inner companions. the high companion fraction of wjs also yields clues to their formation. the wjs that have close-by siblings should have low orbital eccentricities and low mutual inclinations. the orbital configurations of these systems are reminiscent of those of the low-mass close-in planetary systems abundantly discovered by the kepler mission. this, and other arguments, lead us to propose that these wjs are formed in situ. there are indications that there may be a second population of wjs with different characteristics. in this picture, wasp-47b could be regarded as the extending tail of the in situ wjs into the hj region and does not represent the generic formation route for hjs. | warm jupiters are less lonely than hot jupiters: close neighbors |
we present the discovery of a transiting hot jupiter orbiting hip 67522 (teff ∼ 5650 k; m* ∼ 1.2m⊙) in the 10-20 myr old sco-cen ob association. we identified the transits in the tess data using our custom notch filter planet search pipeline and characterize the system with additional photometry from spitzer; spectroscopy from soar/goodman, salt/hrs, lcogt/nres, and smarts/chiron; and speckle imaging from soar/hrcam. we model the photometry as a periodic gaussian process with transits to account for stellar variability and find an orbital period of ${6.9596}_{-0.000015}^{+0.000016}$ days and radius of ${10.02}_{-0.53}^{+0.54}$ r⊕. we also identify a single transit of an additional candidate planet with radius ${8.01}_{-0.71}^{+0.75}$ r⊕ that has an orbital period of ≳23 days. the validated planet hip 67522b is currently the youngest transiting hot jupiter discovered and is an ideal candidate for transmission spectroscopy and radial velocity follow-up studies, while also demonstrating that some young giant planets either form in situ at small orbital radii or else migrate promptly from formation sites farther out in the disk. | tess hunt for young and maturing exoplanets (thyme). ii. a 17 myr old transiting hot jupiter in the sco-cen association |
the isotopic dichotomy between non-carbonaceous (nc) and carbonaceous (cc) meteorites indicates that meteorite parent bodies derive from two genetically distinct reservoirs, which presumably were located inside (nc) and outside (cc) the orbit of jupiter and remained isolated from each other for the first few million years of the solar system. here we review the discovery of the nc-cc dichotomy and its implications for understanding the early history of the solar system, including the formation of jupiter, the dynamics of terrestrial planet formation, and the origin and nature of earth's building blocks. the isotopic difference between the nc and cc reservoirs is probably inherited from the solar system's parental molecular cloud and has been maintained through the rapid formation of jupiter that prevented significant exchange of material from inside (nc) and outside (cc) its orbit. the growth and/or migration of jupiter resulted in inward scattering of cc bodies, which accounts for the co-occurrence of nc and cc bodies in the present-day asteroid belt and the delivery of presumably volatile-rich cc bodies to the growing terrestrial planets. earth's primitive mantle, at least for siderophile elements like mo, has a mixed nc-cc composition, indicating that earth accreted cc bodies during the final stages of its growth, perhaps through the moon-forming giant impactor. the late-stage accretion of cc bodies to earth is sufficient to account for the entire budget of earth's water and highly volatile species. | the non-carbonaceous-carbonaceous meteorite dichotomy |
meteorologists are forecasting a third consecutive year of la niña. some researchers say similar conditions could become more common as the planet warms. | rare `triple' la niña climate event looks likely — what does the future hold? |
we report the latest statistical analyses of superflares on solar-type (g-type main-sequence; effective temperature is 5100-6000 k) stars using all of the kepler primary mission data and gaia data release 2 catalog. we updated the flare detection method from our previous studies by using a high-pass filter to remove rotational variations caused by starspots. we also examined the sample biases on the frequency of superflares, taking into account gyrochronology and flare detection completeness. the sample sizes of solar-type and sun-like stars (effective temperature is 5600-6000 k and rotation period is over 20 days in solar-type stars) are ∼4 and ∼12 times, respectively, compared with notsu et al. as a result, we found 2341 superflares on 265 solar-type stars and 26 superflares on 15 sun-like stars; the former increased from 527 to 2341 and the latter from three to 26 events compared with our previous study. this enabled us to have a more well-established view on the statistical properties of superflares. the observed upper limit of the flare energy decreases as the rotation period increases in solar-type stars. the frequency of superflares decreases as the stellar rotation period increases. the maximum energy we found on sun-like stars is 4 × 1034 erg. our analysis of sun-like stars suggests that the sun can cause superflares with energies of ∼7 × 1033 erg (∼x700-class flares) and ∼1 × 1034 erg (∼x1000-class flares) once every ∼3000 and ∼6000 yr, respectively. | statistical properties of superflares on solar-type stars: results using all of the kepler primary mission data |
magmatism has occurred throughout earth's history. from the early earth to the modern plate-tectonic earth, the amount of magmatism has varied, but it has always occurred on multiple scales, in various tectonic environments and at various depths in the crust and mantle. magma compositions also vary. in this paper, we argue that the mechanism of magma emplacement has generally been passive at all stages of earth evolution. we conclude that most magmatism related to subduction, rifting, mid-oceanic spreading, flood basalts and large igneous provinces and related to mantle upwellings, magma underplating, slab windows, orogenic collisions as well as archean ttg formation are predominantly passive from the lithosphere-scale to the crystal-scale. our results weigh against the view that magmatism drives plate motions. most of the magmatism on other earth-like planets is also passive regardless of the tectonic environments. | passive magmatism on earth and earth-like planets |
reducing society's reliance on fossil fuels presents one of the most pressing energy and environmental challenges facing our planet. hydrogen, methane and carbon dioxide, which are some of the smallest and simplest molecules known, may lie at the centre of solving this problem through realization of a carbon-neutral energy cycle. potentially, this could be achieved through the deployment of hydrogen as the fuel of the long term, methane as a transitional fuel, and carbon dioxide capture and sequestration as the urgent response to ongoing climate change. here we detail strategies and technologies developed to overcome the difficulties encountered in the capture, storage, delivery and conversion of these gas molecules. in particular, we focus on metal-organic frameworks in which metal oxide ‘hubs’ are linked with organic ‘struts’ to make materials of ultrahigh porosity, which provide a basis for addressing this challenge through materials design on the molecular level. | the role of metal-organic frameworks in a carbon-neutral energy cycle |
aircraft observations of meteorological, trace gas, and aerosol properties were made during may-september 2013 in the southeastern united states (us) under fair-weather, afternoon conditions with well-defined planetary boundary layer structure. optical extinction at 532 nm was directly measured at relative humidities (rhs) of ∼ 15, ∼ 70, and ∼ 90 % and compared with extinction calculated from measurements of aerosol composition and size distribution using the κ-köhler approximation for hygroscopic growth. the calculated enhancement in hydrated aerosol extinction with relative humidity, f(rh), calculated by this method agreed well with the observed f(rh) at ∼ 90 % rh. the dominance of organic aerosol, which comprised 65 ± 10 % of particulate matter with aerodynamic diameter < 1 µm in the planetary boundary layer, resulted in relatively low f(rh) values of 1.43 ± 0.67 at 70 % rh and 2.28 ± 1.05 at 90 % rh. the subsaturated κ-köhler hygroscopicity parameter κ for the organic fraction of the aerosol must have been < 0.10 to be consistent with 75 % of the observations within uncertainties, with a best estimate of κ = 0.05. this subsaturated κ value for the organic aerosol in the southeastern us is broadly consistent with field studies in rural environments. a new, physically based, single-parameter representation was developed that better described f(rh) than did the widely used gamma power-law approximation. | aerosol optical properties in the southeastern united states in summer - part 1: hygroscopic growth |
we provide a database of transit times and updated ephemerides for 382 planets based on data from the nasa transiting exoplanet survey satellite (tess) and previously reported transit times, which were scraped from the literature in a semiautomated fashion. in total, our database contains 8667 transit-timing measurements for 382 systems. about 240 planets in the catalog are hot jupiters (i.e., planets with mass >0.3 m jup and period <10 days) that have been observed by tess. the new ephemerides are useful for scheduling follow-up observations and searching for long-term period changes. wasp-12 remains the only system for which a period change is securely detected. we remark on other cases of interest, such as a few systems with suggestive (but not yet convincing) evidence for period changes, and the detection of a second transiting planet in the ngts-11 system. the compilation of light curves, transit times, ephemerides, and timing residuals are made available online, along with the python code that generated them (visit https://transit-timing.github.io). | tess transit timing of hundreds of hot jupiters |
context. exoplanet atmospheres are thought be built up from accretion of gas as well as pebbles and planetesimals in the midplanes of planet-forming disks. the chemical composition of this material is usually assumed to be unchanged during the disk lifetime. however, chemistry can alter the relative abundances of molecules in this planet-building material.aims: we aim to assess the impact of disk chemistry during the era of planet formation. this is done by investigating the chemical changes to volatile gases and ices in a protoplanetary disk midplane out to 30 au for up to 7 myr, considering a variety of different conditions, including a physical midplane structure that is evolving in time, and also considering two disks with different masses.methods: an extensive kinetic chemistry gas-grain reaction network was utilised to evolve the abundances of chemical species over time. two disk midplane ionisation levels (low and high) were explored, as well as two different makeups of the initial abundances ("inheritance" or "reset").results: given a high level of ionisation, chemical evolution in protoplanetary disk midplanes becomes significant after a few times 105 yr, and is still ongoing by 7 myr between the h2o and the o2 icelines. inside the h2o iceline, and in the outer, colder regions of the disk midplane outside the o2 iceline, the relative abundances of the species reach (close to) steady state by 7 myr. importantly, the changes in the abundances of the major elemental carbon and oxygen-bearing molecules imply that the traditional "stepfunction" for the c/o ratios in gas and ice in the disk midplane (as defined by sharp changes at icelines of h2o, co2 and co) evolves over time, and cannot be assumed fixed, with the c/o ratio in the gas even becoming smaller than the c/o ratio in the ice. in addition, at lower temperatures (<29 k), gaseous co colliding with the grains gets converted into co2 and other more complex ices, lowering the co gas abundance between the o2 and co thermal icelines. this effect can mimic a co iceline at a higher temperature than suggested by its binding energy.conclusions: chemistry in the disk midplane is ionisation-driven, and evolves over time. this affects which molecules go into forming planets and their atmospheres. in order to reliably predict the atmospheric compositions of forming planets, as well as to relate observed atmospheric c/o ratios of exoplanets to where and how the atmospheres have formed in a disk midplane, chemical evolution needs to be considered and implemented into planet formation models. | molecular abundances and c/o ratios in chemically evolving planet-forming disk midplanes |
we present 3d smoothed particle hydrodynamics simulations of protoplanetary discs undergoing a flyby by a stellar perturber on a parabolic orbit lying in a plane inclined relative to the disc mid-plane. we model the disc as a mixture of gas and dust, with grains ranging from 1 μm to 10 cm in size. exploring different orbital inclinations, periastron distances, and mass ratios, we investigate the disc dynamical response during and after the flyby. we find that flybys induce evolving spiral structure in both gas and dust that can persist for thousands of years after periastron. gas and dust structures induced by the flyby differ because of drag-induced effects on the dust grains. variations in the accretion rate by up to an order of magnitude occur over a time-scale of the order of 10 yr or less, inducing fu orionis-like outbursts. the remnant discs are truncated and warped. the dust disc is left more compact than the gas disc, both because of disc truncation and accelerated radial drift of grains induced by the flyby. | flybys in protoplanetary discs: i. gas and dust dynamics |
massive stars, which terminate their evolution in a cataclysmic explosion called a type-ii supernova, are the nuclear engines of galactic nucleosynthesis. among the elemental species known to be produced in these stars, the radioisotope 60fe stands out: this radioisotope has no natural, terrestrial production mechanisms; thus, a detection of 60fe atoms within terrestrial reservoirs is proof for the direct deposition of supernova material within our solar system. we report, in this work, the direct detection of live 60fe atoms in biologically produced nanocrystals of magnetite, which we selectively extracted from two pacific ocean sediment cores. we find that the arrival of supernova material on earth coincides with the lower pleistocene boundary (2.7 ma) and that it terminates around 1.7 ma. | time-resolved 2-million-year-old supernova activity discovered in earth's microfossil record |
coherent low-frequency (≲200 mhz) radio emission from stars encodes the conditions of the outer corona, mass-ejection events and space weather1-5. previous low-frequency searches for radio-emitting stellar systems have lacked the sensitivity to detect the general population, instead largely focusing on targeted studies of anomalously active stars5-9. here we present 19 detections of coherent radio emission associated with known m dwarfs from a blind flux-limited low-frequency survey. our detections show that coherent radio emission is ubiquitous across the m dwarf main sequence, and that the radio luminosity is independent of known coronal and chromospheric activity indicators. while plasma emission can generate the low-frequency emission from the most chromospherically active stars of our sample1,10, the origin of the radio emission from the most quiescent sources is yet to be ascertained. large-scale analogues of the magnetospheric processes seen in gas giant planets3,11,12 probably drive the radio emission associated with these quiescent stars. the slowest-rotating stars of this sample are candidate systems to search for star-planet interaction signatures. | the population of m dwarfs observed at low radio frequencies |
exoplanet detection with precise radial velocity (rv) observations is currently limited by spurious rv signals introduced by stellar activity. we show that machine-learning techniques such as linear regression and neural networks can effectively remove the activity signals (due to starspots/faculae) from rv observations. previous efforts focused on carefully filtering out activity signals in time using modeling techniques like gaussian process regression. instead, we systematically remove activity signals using only changes to the average shape of spectral lines, and use no timing information. we trained our machine-learning models on both simulated data (generated with the soap 2.0 software) and observations of the sun from the harps-n solar telescope. we find that these techniques can predict and remove stellar activity both from simulated data (improving rv scatter from 82 to 3 cm s-1) and from more than 600 real observations taken nearly daily over 3 yr with the harps-n solar telescope (improving the rv scatter from 1.753 to 1.039 m s-1, a factor of ~1.7 improvement). in the future, these or similar techniques could remove activity signals from observations of stars outside our solar system and eventually help detect habitable-zone earth-mass exoplanets around sun-like stars. | identifying exoplanets with deep learning. iv. removing stellar activity signals from radial velocity measurements using neural networks |
we present a comprehensive analysis of planetary phase variations, including possible planetary light offsets, using eighteen quarters of data from the kepler space telescope. our analysis found fourteen systems with significant detections in each of the phase curve components: planet’s phase function, secondary eclipse, doppler boosting, and ellipsoidal variations. we model the full phase curve simultaneously, including primary and secondary transits, and derive albedos, day- and night-side temperatures and planet masses. most planets manifest low optical geometric albedos (< 0.25), with the exception of kepler-10b, kepler-91b, and koi-13b. we find that koi-13b, with a small eccentricity of 0.0006 ± 0.0001, is the only planet for which an eccentric orbit is favored. we detect a third harmonic for hat-p-7b for the first time, and confirm the third harmonic for koi-13b reported in esteves et al.: both could be due to their spin-orbit misalignments. for six planets, we report a planetary brightness peak offset from the substellar point: of those, the hottest two (kepler-76b and hat-p-7b) exhibit pre-eclipse shifts or on the evening-side, while the cooler four (kepler-7b, kepler-8b, kepler-12b, and kepler-41b) peak post-eclipse or on the morning-side. our findings dramatically increase the number of kepler planets with detected planetary light offsets, and provide the first evidence in the kepler data for a correlation between the peak offset direction and the planet’s temperature. such a correlation could arise if thermal emission dominates light from hotter planets that harbor hot spots shifted toward the evening-side, as theoretically predicted, while reflected light dominates cooler planets with clouds on the planet’s morning-side. | changing phases of alien worlds: probing atmospheres of kepler planets with high-precision photometry |
the moniker rubble pile is typically applied to all solar system bodies >200 m and ≲10 km in diameter; in this size range, there is an abundance of evidence that nearly every object is bound primarily by self-gravity, with significant void space or bulk porosity between irregularly shaped constituent particles. the understanding of this population is derived from wide-ranging population studies of derived shape and spin, decades of observational studies in numerous wavelengths, evidence left behind from impacts on planets and moons, and the in situ study of a few objects via spacecraft flyby or rendezvous. the internal structure, however, which is responsible for the name rubble pile, is never directly observed but belies a violent history. many or most of the asteroids on near-earth orbits and those most accessible for rendezvous and in situ study are likely by-products of the continued collisional evolution of the main asteroid belt. | rubble pile asteroids |
the planetary boundary layer height (pblh) is a very important parameter in the atmosphere, because it determines the range where the most effective dispersion processes take place, and serves as a constraint on the vertical transport of heat, moisture, and pollutants. as the only space-borne lidar, cloud-aerosol lidar with orthogonal polarization onboard cloud-aerosol lidar and infrared pathfinder satellite observations (calipso) measures the vertical distribution of aerosol signals and thus offers the potential to retrieve large-scale pblh climatology. in this study, we explore different techniques for retrieving pblh from calipso measurements and validate the results against those obtained from ground-based micropulse lidar (mpl) and radiosonde (rs) data over hong kong, where long-term mpl and rs measurements are available. two methods, namely maximum standard deviation (msd) and wavelet covariance transform (wct), are used to retrieve pblh from calipso. results show that the rs- and mpl-derived pblhs share similar interannual variation and seasonality and can complement each other. both msd and wct perform reasonably well compared with mpl/rs products, especially under sufficient aerosol loading. uncertainties increase when aerosol loading is low and the calipso signal consequently becomes noisier. overall, calipso captures the general pblh seasonal variability over hong kong, despite a high bias in spring and a low bias in summer. the spring high bias is likely associated with elevated aerosol layers due to transport, while the summer low bias can be attributed to higher noise level associated with weaker aerosol signal. | an intercomparison of long-term planetary boundary layer heights retrieved from calipso, ground-based lidar, and radiosonde measurements over hong kong |
context. until recently, camera networks designed for monitoring fireballs worldwide were not fully automated, implying that in case of a meteorite fall, the recovery campaign was rarely immediate. this was an important limiting factor as the most fragile - hence precious - meteorites must be recovered rapidly to avoid their alteration.aims: the fireball recovery and interplanetary observation network (fripon) scientific project was designed to overcome this limitation. this network comprises a fully automated camera and radio network deployed over a significant fraction of western europe and a small fraction of canada. as of today, it consists of 150 cameras and 25 european radio receivers and covers an area of about 1.5 × 106 km2.methods: the fripon network, fully operational since 2018, has been monitoring meteoroid entries since 2016, thereby allowing the characterization of their dynamical and physical properties. in addition, the level of automation of the network makes it possible to trigger a meteorite recovery campaign only a few hours after it reaches the surface of the earth. recovery campaigns are only organized for meteorites with final masses estimated of at least 500 g, which is about one event per year in france. no recovery campaign is organized in the case of smaller final masses on the order of 50 to 100 g, which happens about three times a year; instead, the information is delivered to the local media so that it can reach the inhabitants living in the vicinity of the fall.results: nearly 4000 meteoroids have been detected so far and characterized by fripon. the distribution of their orbits appears to be bimodal, with a cometary population and a main belt population. sporadic meteors amount to about 55% of all meteors. a first estimate of the absolute meteoroid flux (mag < -5; meteoroid size ≥~1 cm) amounts to 1250/yr/106 km2. this value is compatible with previous estimates. finally, the first meteorite was recovered in italy (cavezzo, january 2020) thanks to the prisma network, a component of the fripon science project. | fripon: a worldwide network to track incoming meteoroids |
we present an analysis of over 23,000 globally distributed wildfire smoke plume injection heights derived from multi-angle imaging spectroradiometer (misr) space-based, multi-angle stereo imaging. both pixel-weighted and aerosol optical depth (aod)-weighted results are given, stratified by region, biome, and month or season. this offers an observational resource for assessing first-principle plume-rise modelling, and can provide some constraints on smoke dispersion modelling for climate and air quality applications. the main limitation is that the satellite is in a sun-synchronous orbit, crossing the equator at about 10:30 a.m. local time on the day side. overall, plumes occur preferentially during the northern mid-latitude burning season, and the vast majority inject smoke near-surface. however, the heavily forested regions of north and south america, and africa produce the most frequent elevated plumes and the highest aod values; some smoke is injected to altitudes well above 2 km in nearly all regions and biomes. planetary boundary layer (pbl) versus free troposphere injection is a critical factor affecting smoke dispersion and environmental impact, and is affected by both the smoke injection height and the pbl height; an example assessment is made here, but constraining the pbl height for this application warrants further work. | a global analysis of wildfire smoke injection heights derived from space-based multi-angle imaging |
giant kelp (macrocystis pyrifera) is the most widely distributed kelp species on the planet, constituting one of the richest and most productive ecosystems on earth, but detailed information on its distribution is entirely missing in some marine ecoregions, especially in the high latitudes of the southern hemisphere. here, we present an algorithm based on a series of filter thresholds to detect giant kelp employing sentinel-2 imagery. given the overlap between the reflectances of giant kelp and intertidal green algae (ulvophyceae), the latter are also detected on shallow rocky intertidal areas. the kelp filter algorithm was applied separately to vegetation indices, the floating algae index (fai), the normalised difference vegetation index (ndvi), and a novel formula (the kelp difference, kd). training data from previously surveyed kelp forests and other coastal and ocean features were used to identify reflectance threshold values. this procedure was validated with independent field data collected with uav imagery at a high spatial resolution and point-georeferenced sites at a low spatial resolution. when comparing uav with sentinel data (high-resolution validation), an average overall accuracy ≥ 0.88 and cohen's kappa ≥ 0.64 coefficients were found in all three indices for canopies reaching the surface with extensions greater than 1 hectare, with the kd showing the highest average kappa score (0.66). measurements between previously surveyed georeferenced points and remotely-sensed kelp grid cells (low-resolution validation) showed that 66% of the georeferenced points had grid cells indicating kelp presence within a linear distance of 300 m. we employed the kd in our kelp filter algorithm to estimate the global extent of giant kelp and intertidal green algae per marine ecoregion and province, producing a high-resolution global map of giant kelp and intertidal green algae, powered by google earth engine. | a high-resolution global map of giant kelp (macrocystis pyrifera) forests and intertidal green algae (ulvophyceae) with sentinel-2 imagery |
high-latitude environments store nearly half of the planet's below-ground organic carbon (oc), mostly in perennially frozen permafrost soils. climatic changes drive increased export of terrestrial oc into many aquatic networks, yet the role that circumpolar lakes play in mineralizing this carbon is unclear. here we directly evaluate ecosystem-scale oc cycling for lakes of interior alaska. this arid, low-relief lake landscape is representative of over a quarter of total northern circumpolar lake area, but is greatly under-represented in current studies. contrary to projections based on work in other regions, the studied lakes had a negligible role in mineralizing terrestrial carbon; they received little oc from ancient permafrost soils, and had small net contribution to the watershed carbon balance. instead, most lakes recycled large quantities of internally derived carbon fixed from atmospheric co2, underscoring their importance as critical sites for material and energy provision to regional food webs. our findings deviate from the prevailing paradigm that northern lakes are hotspots of terrestrial oc processing. the shallow and hydrologically disconnected nature of lakes in many arid circumpolar landscapes isolates them from terrestrial carbon processing under current climatic conditions. | negligible cycling of terrestrial carbon in many lakes of the arid circumpolar landscape |
the impact of the planetary boundary layer (pbl) structure on air pollution in northeast china, where frequently experiences air pollution episodes in autumn and winter, is not well understood due to a lack of observations. in this study, four pollution episodes during autumn and winter of 2016 at shenyang, a provincial capital city in northeast china, were examined to investigate the linkage between the pbl structure and air pollution using meteorological sounding data and lidar-retrieved profiles of aerosol extinction coefficients. we also conducted a tracer simulation using the weather research and forecasting model with chemistry (wrf-chem) to demonstrate the transport and vertical mixing of air pollutants in the pbl. the results indicated that a stable, moist and shallow surface layer (<400 m) formed and remained at night due to strong surface radiative cooling after a steep decline of temperature during the first air-pollution episode (ep1, from 12:00 local time (lt) on november 26 to 07:00 lt on november 27). stable stratification and stagnant winds contributed to the increase of surface pollutant concentrations in ep1. strong surface potential temperature inversion and enhanced local emissions during evening rush hour resulted in the formation of ep2 (13:00-23:00 lt on december 2). observations and modelling results revealed that large amount of pollutants were transported by the southerly nocturnal low-level jets from the north china plain to shenyang after ep2. these pollutants were trapped in the residue layer at night and then mixed to the surface after sunrise due to convective turbulence, leading to the formation of ep3 (06:00-23:00 lt on december 3). ep4 (03:00-14:00 lt on december 4) occurred in the convergence zone ahead of an approaching trough. low wind speed (<6 m s-1) and high relative humidity (>80%) in the pbl enhanced the deterioration of air quality near the surface. | impact of planetary boundary layer structure on the formation and evolution of air-pollution episodes in shenyang, northeast china |
this review examines recent theoretical developments in our understanding of turbulence in cold, non-magnetically active, planetesimal-forming regions of protoplanetary disks that we refer to throughout as “ohmic zones.” we give a brief background introduction to the subject of disk turbulence followed by a terse pedagogical review of the phenomenology of hydrodynamic turbulence. the equations governing the dynamics of cold astrophysical disks are given and basic flow states are described. we discuss the solberg-høiland conditions required for stability, and the three recently identified turbulence-generating mechanisms that are possibly active in protoplanetary disk ohmic zones: (i) the vertical shear instability, (ii) the convective overstability, and (iii) the zombie vortex instability. we summarize the properties of these processes, identify their limitations, and discuss where and under what conditions these processes are active in protoplanetary disk ohmic zones. | the initial conditions for planet formation: turbulence driven by hydrodynamical instabilities in disks around young stars |
kelt-9 b, the hottest known exoplanet, with teq ~ 4400 k, is the archetype of a new planet class known as ultra-hot jupiters. these exoplanets are presumed to have an atmosphere dominated by neutral and ionized atomic species. in particular, hα and hβ balmer lines have been detected in the kelt-9 b upper atmosphere, suggesting that hydrogen is filling the planetary roche lobe and escaping from the planet. in this work, we detected δ scuti-type stellar pulsation (with a period ppuls = 7.54 ± 0.12 h) and studied the rossiter-mclaughlin effect (finding a spin-orbit angle λ = -85.01° ± 0.23°) prior to focussing on the balmer lines (hα to hζ) in the optical transmission spectrum of kelt-9 b. our harps-n data show significant absorption for hα to hδ. the precise line shapes of the hα, hβ, and hγ absorptions allow us to put constraints on the thermospheric temperature. moreover, the mass loss rate, and the excited hydrogen population of kelt-9 b are also constrained, thanks to a retrieval analysis performed with a new atmospheric model. we retrieved a thermospheric temperature of t = 13 200-720+800 k and a mass loss rate of ṁ = 1012.8±0.3 g s-1 when the atmosphere was assumed to be in hydrodynamical expansion and in local thermodynamic equilibrium (lte). since the thermospheres of hot jupiters are not expected to be in lte, we explored atmospheric structures with non-boltzmann equilibrium for the population of the excited hydrogen. we do not find strong statistical evidence in favor of a departure from lte. however, our non-lte scenario suggests that a departure from the boltzmann equilibrium may not be sufficient to explain the retrieved low number densities of the excited hydrogen. in non-lte, saha equilibrium departure via photo-ionization, is also likely to be necessary to explain the data. based on observations made at tng (telescopio nazionale galileo) telescope with the harps-n spectrograph under program a35ddt4 and opticon 2018a/038. | mass-loss rate and local thermodynamic state of the kelt-9 b thermosphere from the hydrogen balmer series |
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