page_content stringlengths 12 2.63M | metadata unknown |
|---|---|
It has over 1% of Earth's mass and is surpassed in this respect only by Pluto's satellite Charon. It has a dry,barren,atmosphereless surface that has been heavily cratered by impacts of asteroids and comets and that bears mute evidence of extensive episodic melting during the first billion years of its existence. The h... | {
"Header 1": "Satellites",
"token_count": 1150,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
In a wide belt between the orbits of Mars and Jupiter there are many thousands of small rocky bodies,most of them in orbits of modest eccentricity and inclination. The orbital elements of these belt asteroids are far from uniformly distributed over the space available. There are many very sharply defined maxima and min... | {
"Header 1": "Asteroids",
"token_count": 2016,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Indirect techniques based on simultaneous measurement of the visual and infrared brightness of optically unresolved bodies have provided good size estimates for hundreds of asteroids (see Chapter VIII). Polarimetry also provides an independent estimate of the albedos and sizes of many asteroids. A few near-Earth astero... | {
"Header 1": "Asteroids",
"token_count": 412,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
One of the most spectacular phenomena in the Solar System is the apparition of a bright comet. Throughout history the sudden appearance and rapid development of bright comets have inspired prophecies of doom and engendered civil disorder during the days or weeks that they are visible in the sky.
Comets fall into two ... | {
"Header 1": "Comets",
"token_count": 2014,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The bright,fast-moving streaks of light often seen in the night sky are called meteors. They are caused by the entry of small solid particles of cometary or asteroidal debris,called meteoroids,into Earth's upper atmosphere at such high speeds that they flash into incandescent vapor in a fraction of a second.. Most of t... | {
"Header 1": "Meteors",
"token_count": 339,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Meteorites are defined as solid macroscopic bodies that survive entry into Earth's atmosphere. They are not associated in any way with shower meteors and are so rare that they are not often observed to enter the atmosphere. Although an observer can see several meteors per hour on almost any clear,dark night,meteorites ... | {
"Header 1": "Meteorites",
"token_count": 584,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
As we mentioned in our brief discussion of the Sun, particles (mostly protons) with energies up to several hundred MeV are emitted by the Sun during periods of intense flare activity. These particles are termed solar
Figure III.11 Two bright meteors. They were photographed by Donald Pea... | {
"Header 1": "Cosmic Rays",
"token_count": 289,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
A very large proportion of human knowledge of the planets,satellites,and other Solar System bodies comes directly from spacecraft exploration of the Solar System.
Table III.8 Prominent Meteor Showers
| | | | Radiant | |
|----------------|--------------|-----------... | {
"Header 1": "Planetary Science in the Space Age",
"token_count": 1951,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The physical and chemical properties of solar material play a central role in any discussion of the origin of the Solar System, the properties of the Jovian planets, or the Sun itself. The Sun, in turn, serves as our prototype for the study of all other stars. The raw interstellar material out of which stellar and plan... | {
"Header 1": "Introduction",
"token_count": 400,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The major nuclear reactions involved in hydrogen fusion are collected in Table IV.1. These reactions have for the most part been discussed in Chapter II, and a detailed discussion will not be repeated here.
Table IV.1 Nuclear Reactions in the Sun
$$\begin{array}{c}
& 12C + {}^{1}H \rightarrow {}^{13}N \\
& {}^{13}N... | {
"Header 1": "Energy Production in the Sun",
"token_count": 2016,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
This isotope decays via
$$^{8}\text{B} \rightarrow 2\,^{4}\text{He} + \,\mathrm{e}^{+} + \nu,$$
(IV.7)
giving off 14-MeV neutrinos, which have, according to Eq. (IV.5), 780 times the interaction cross section of p-p chain rate. This greatly enhanced detectability largely compensates for their much lower production.... | {
"Header 1": "Energy Production in the Sun",
"token_count": 600,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
In order to develop a steady-state model for the structure of the Sun, it is first necessary to examine the mechanisms by which heat may be transported from the site of nuclear reactions in the deep interior out to the radiating surface, the photosphere. Because of the obvious importance of radiation in the Sun, we sha... | {
"Header 1": "Energy Transport in the Sun",
"token_count": 2039,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
In a large ensemble of atoms, a very wide range of collision energies and geometries can all be found at once. Accordingly, the region of the former absorption band of narrow, sharp lines becomes a broad, almost featureless region of absorption (or emission). This collisional broadening, usually called by the less evoc... | {
"Header 1": "Energy Transport in the Sun",
"token_count": 1979,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Equating to the total internal thermal energy, we have
$$4 \times 10^{48} = (3/2)N_{\odot}kT_{\odot},$$
(IV.32)
where $N_{\odot}$ is the number of particles in the Sun,
$$N_{\odot} = 2N_{\odot}M_{\odot} = 2 \times 10^{57}$$
. (IV.33)
Solving for $T_{\odot}$ , the mean internal temperature of the Sun, we get ... | {
"Header 1": "Energy Transport in the Sun",
"token_count": 2040,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
During the eruption of these solar flares the luminosity of the Sun may increase by 0.1 to 1%. Much larger luminosity increases are seen at ultraviolet wavelengths, where the Sun normally exhibits a blackbody temperature of 3000 to 4000 K. The magnetic fields associated with flares are on the order of 1000 gauss (G) co... | {
"Header 1": "Energy Transport in the Sun",
"token_count": 2028,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The thin chromospheric layer is normally detectable because of the absorption lines that it superimposes on the solar spectrum. All told, these lines absorb some 10% or more of the total solar flux. During total eclipses of the Sun, the solar photosphere is covered fully only seconds before the chromosphere is itself e... | {
"Header 1": "The Chromosphere",
"token_count": 461,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Over a century ago there were three lines of evidence for a coupling between phenomena on the solar surface and events distant from the Sun. First, geomagnetic variations and auroral displays on Earth often showed the same periodicity as the synodic rotation of the Sun (its rotation as seen from Earth). Second, comet t... | {
"Header 1": "The Corona",
"token_count": 2041,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
ISPM, a joint venture of the United States and the Federal Republic of Germany, originally involved launching of two spacecraft into Jupiter flybys, which were to be used to twist the orbital planes of the spacecraft to orbits with about $+80^{\circ}$ and $-80^{\circ}$ inclinations, respectively. This would have pe... | {
"Header 1": "The Corona",
"token_count": 504,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The first evidence suggestive of the existence of a radial outflow of very hot ionized gas (plasma) from the Sun was the observation about a century ago that there was a close correlation between solar flares and terrestrial auroral activity, which frequently became prominent a few days after a major flare. The disturb... | {
"Header 1": "Discovery of the Solar Wind",
"token_count": 900,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
At present, in addition to in situ spacecraft measurements of the local properties of the solar wind, both Earth-based and spacecraft-based radiophysical studies of the large-scale structure are being actively pursued. Interplanetary and lunar spacecraft launched by the United States and the former USSR routinely carry... | {
"Header 1": "Radio Wave Propagation in Space Plasmas",
"token_count": 2045,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Such scintillation measurements provide an additional probe of conditions in the corona and solar wind.
#### The Solar Wind
The general picture of the solar wind that has emerged in the course of modern spacecraft measurements is in its essential elements rather simple. The dense, hot solar atmosphere at the base o... | {
"Header 1": "Radio Wave Propagation in Space Plasmas",
"token_count": 2038,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The first attempts to model the solar wind structure and flow were presented by Eugene N. Parker of the University of Chicago several years before the direct detection of the wind by spacecraft experiments, in response to Biermann's work on the acceleration and aberration of comet tails. This work showed speeds of $... | {
"Header 1": "Radio Wave Propagation in Space Plasmas",
"token_count": 2001,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
(IV.85) is thus
$$(V^2 - 2V_t^2/3)dV/Vdr$$
= $(4V_t^2/3r)[1 - r_0/r]$ . (IV.85c)
Separating variables, we have
$$(V^2 - 2V_t^2/3)(dV/V) = (4V_t^2/3r)(1 - r_0/r)dr.$$
(IV.85d)
There are six classes of solutions to this equation, as shown in Fig. IV.12. Some of the solutions have clearly unacceptable forms, su... | {
"Header 1": "Radio Wave Propagation in Space Plasmas",
"token_count": 1861,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
low-temperature product | $El(OH)_3$ |
The processes $a \rightarrow b, b \rightarrow c$ , etc., occur during cooling at well-defined lines in pressure-temperature space, each defined by an equilibrium:
$$\begin{array}{lll} a \rightarrow b & El^{+z} + e^- \leftright... | {
"Header 1": "Radio Wave Propagation in Space Plasmas",
"token_count": 1993,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Table IV.4 Atomic Ionization Potentials
| | Energy required to remove each electron (eV) | | | | | |
|------|----------------------------------------------|-------|-------|-------|--|--|
| Atom | 1 | 2 | 3 | 4 | | |
| Н | 13.60 ... | {
"Header 1": "Radio Wave Propagation in Space Plasmas",
"token_count": 1927,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
If we desire to insert another element, such as oxygen, then
$$O = O^+ + e^-$$
(IV.90)
$$K_{90}(T) = (p_{\text{O}}^+ p_{\text{e}}^-)/p_{\text{O}}$$
(IV.90a)
and we need only add a new equation to conserve oxygen,
$$p_{\mathcal{O}} + p_{\mathcal{O}^+} = \Sigma \mathcal{O}, \qquad (IV.90b)$$
apply the cosmic ab... | {
"Header 1": "Radio Wave Propagation in Space Plasmas",
"token_count": 584,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
At temperatures below about 2000 K, the overwhelming majority of the atoms of every element are neutral, not ionic. In this temperature range kT is comparable to the strengths of some of the strongest chemical bonds, and diatomic and polyatomic molecules may form.
The most universal example of this process is provide... | {
"Header 1": "Dissociation and Molecule Formation",
"token_count": 1402,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
A simple introduction to the equilibrium chemical behavior of solar material is provided by summarizing what we have so far learned about hydrogen. Figure IV.14 shows the major features of the behavior of hydrogen from 10<sup>9</sup> to 10 bar total pressure over the temperature range from about 10,000 K down to absolu... | {
"Header 1": "Hydrogen and the Rare Gases",
"token_count": 1461,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
After hydrogen and helium, the next most abundant element in the cosmos is oxygen. (It is a bit startling to the novice geology student to hear for the first time that the most abundant element in the Earth is oxygen, due to the prevalence of oxide minerals in the Earth.) Immediately after oxygen in cosmic abundance co... | {
"Header 1": "Oxygen, Carbon, and Nitrogen",
"token_count": 1983,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Then
$$f_{\text{NH}_3} = P(K_{105}f_{\text{N}_2}(f_{\text{H}_2}^3)^{1/2} \propto P$$
(IV.114)
On the high-pressure side of the boundary, the ammonia mole fraction is constant at twice this level, and the $N_2$ mole fraction is a strong function of pressure:
$$f_{\rm N_2} = \frac{(f_{\rm NH_3})^2}{(f_{\rm H_2})^... | {
"Header 1": "Oxygen, Carbon, and Nitrogen",
"token_count": 2019,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
\label{eq:siO}$$
$$\underset{forsterite}{enstatite} (IV.121)$$
Here, as elsewhere, solids (s) and liquids (l) are marked as such, or mineral names are given, whereas gases are left unmarked. Because the abundance of magnesium is almost exactly equal to the abundance of silicon, cooling to the point of complete cond... | {
"Header 1": "Oxygen, Carbon, and Nitrogen",
"token_count": 2046,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The general formula for olivine which reflects the allowed range of compositions is $(Fe, Mg)_2SiO_4$ .
Substitution of FeO for MgO also occurs in enstatite. Solid solutions ranging in composition from FeSiO<sub>3</sub> (ferrosilite) to MgSiO<sub>3</sub> (enstatite) are members of the pyroxene family, which we shall... | {
"Header 1": "Oxygen, Carbon, and Nitrogen",
"token_count": 1215,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Near 2000 K, sulfur is found largely as SiS and the SH (sulfhydryl) radical, although traces of SO, COS, and CS are also present. Solid sulfides of silicon are quite unstable, and hence SiS does not condense. Instead, SiS (and SH) are converted to H2S during cooling.
The first and most important sulfide to form is Fe... | {
"Header 1": "Sulfur",
"token_count": 633,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Calcium and aluminum oxides are very refractory substances with high melting points and low vapor pressures that are commonly used as the major constituents
Figure IV.19 Distribution of iron between its minerals. The fraction of total iron in the monatomic iron vapor, in solid metallic ... | {
"Header 1": "Aluminum and Calcium",
"token_count": 926,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Atomic sodium and potassium vapor, Na and K, remain in the gas phase until completion of the condensation of enstatite. At slightly lower temperatures it becomes possible for the alkali metal vapors to react with aluminum-bearing minerals to produce alkali aluminosilicates. A simple conceptual example would be
$$\beg... | {
"Header 1": "Sodium and Potassium",
"token_count": 1729,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The chemical properties of Ni and Co are closely similar to those of iron. Both are slightly enriched in the first metal to condense, but then, in the temperature regime from about 1400 K down to 680 K, their ratios to iron in the metal phase are very close to the solar Ni:Fe abundance ratio.
Several different phases... | {
"Header 1": "Nickel and Cobalt",
"token_count": 656,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
There are several gaseous phosphorus compounds that are important at elevated temperatures, notably PN, PO, PS, and P. Phosphorus, like carbon, enters the metal phase in extremely small quantities (0.01% of total P) at elevated temperatures. Solid schreibersite, Fe3P, is the only important carrier of phosphorus down to... | {
"Header 1": "Phosphorus and the Halogens",
"token_count": 350,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
We have now discussed the main features of the equilibrium chemistry of 20 of the 23 most abundant elements in the Sun, plus the heavy rare gases krypton and xenon. If the principle of equal time were applied to the remainder of the periodic table, we would become obliged to convert this chapter into a bookin its own r... | {
"Header 1": "Geochemical Classification of the Elements",
"token_count": 2035,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The minerals formed by the major elements are sketched. The three different temperature–pressure profiles correspond to isobaric (constant pressure), isopycnic (constant density), and adiabatic (constant entropy) structures. Note the extreme similarity of the condensation sequences for these very different sets of cond... | {
"Header 1": "Geochemical Classification of the Elements",
"token_count": 1804,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Now that we have explored the conceptually (and computationally) simplest model for the chemical behavior of solar material, let us examine the consequences of a completely different assumption regarding the relative rates of accretion and chemical equilibration. Heretofore we have assumed that accretion of solids to f... | {
"Header 1": "The Chemistry of Rapid Accretion",
"token_count": 2009,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
If the solids in the inner Solar System in fact result from unidirectional cooling from an extremely hot gas (rather than, say, equilibration at some maximum
Figure IV.31 Condensation in the nonhomogeneous accretion model. This figure should be compared with the equilibrium condensation... | {
"Header 1": "Kinetic Inhibition",
"token_count": 624,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
We have seen from our discussion of the chemistry of solar material that the fraction of the total mass of a solar-composition gas that is ''rocky'' is very small, only about 0.4% of the total mass. About 98.2% of the mass is accounted for by the ''permanent'' gases, and 1.4% by ''ices.'' This means that the minimum ma... | {
"Header 1": "Mass and Density of the Solar Nebula",
"token_count": 2020,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Centrifugal, directed radially outward from the rotation axis of the nebula, parallel to the central symmetry plane of the disk, and
- c. Pressure gradient, directed generally ''upward'' (in the z direction, perpendicular to the diskplane) and ''outward'' (in the r direction). For the purposes of an approximate steady-... | {
"Header 1": "Mass and Density of the Solar Nebula",
"token_count": 2044,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
This opacity is due in part to infrared absorption by molecules, and partly to dust. We have already seen the nature of the electronic absorption spectrum of atomic hydrogen. We have also examined the chemistry of hydrogen over a very wide range of temperatures and pressures and have crudely assessed both the temperatu... | {
"Header 1": "Mass and Density of the Solar Nebula",
"token_count": 2040,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Because the water molecule is nonlinear and triatomic, it has more than one possible vibrational mode. In fact, it has three, each with a characteristic frequency.
Any diatomic molecule can both vibrate and rotate. Table IV.9 enumerates the different independent (orthogonal) modes available to a wide variety of molec... | {
"Header 1": "Mass and Density of the Solar Nebula",
"token_count": 2011,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
In Appendix I, we prove that the heat capacity at constant pressure, CP, is C<sup>V</sup> þ R ¼ 5R/2.
The rotational fundamental of hydrogen gas is at 17 m, which, from Fig. IV.38, requires a collision with a molecule at about 200 K to excite. Above about 200 K, therefore, heating the gas through dT requires supplyin... | {
"Header 1": "Mass and Density of the Solar Nebula",
"token_count": 1940,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
(For Doppler broadening under the same conditions, $\Delta \nu = \nu V/c = 10^{14} (10^5/3 \times 10^{10}) = \text{only } 3 \times 10^8 \text{ Hz.}$ ) Because
$$l = kT/\pi r^2 P (IV.164)$$
and
$$V = (kT/m)^{1/2},$$
(IV.165)
we get
$$\Delta E = h/2\Delta t = hv/l = hV/l$$
= $\pi ha^2 P/(mkT)^{1/2}$ , (IV.1... | {
"Header 1": "Mass and Density of the Solar Nebula",
"token_count": 2025,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Although condensates make up a very small fraction of the mass of the nebula, they can be important sources of opacity if they are good absorbers or scatterers. As with gases, we can analyze the absorption of electromagnetic energy in terms of electronic, vibrational, and rotational transitions; however, in solids it i... | {
"Header 1": "Dust Opacity",
"token_count": 2039,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
We have seen, in our discussion of solar physics, that the temperature gradient in a gas is related to its opacity and the heat flux through it by
$$(dT/dr) = -3K\rho F(r)/4\sigma T^{3} = 3\alpha F(r)/4\sigma T^{3}$$
. (IV.18)
Taking ¼ 107, ¼ 5:67 105, and T ¼ 1000 K, we get
$$(dT/dr) = 1.3 \times 10^{-12} F(r).$... | {
"Header 1": "Thermal Structure of the Nebula",
"token_count": 1988,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
We have now used our limits on $\sigma(r)$ deduced from the mass distribution in the Solar System in combination with our deduction of adiabatic structure for the nebula to predict the radial variations of the midplane temperature and pressure, $P_c(r)$ and $T_c(r)$ . We will now turn to the available data on th... | {
"Header 1": "Thermal Structure of the Nebula",
"token_count": 1293,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
As long as the opacity of the nebula remains high, it will maintain a steep temperature gradient and be convective. If the dust grains, which are the principal source of continuum infrared opacity, settle quickly into the central plane of the nebula, then the thermal opacity will vanish and turbulence will virtually ce... | {
"Header 1": "Turbulence and Dust Sedimentation",
"token_count": 2037,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The force on a body due to solar gravity, the centripetal force necessary to maintain circular motion, the pressure gradient force, and the gas turbulence force are, respectively,
$$F_{\rm g} = GMm/r^2 \tag{IV.192}$$
$$F_{\rm c} = mV_K^2/r \tag{IV.193}$$
$$F_{\rm P} = (m/\rho_{\rm body})(dP/dr) \qquad (IV.194)$$ ... | {
"Header 1": "Turbulence and Dust Sedimentation",
"token_count": 1314,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
We have seen that gas motions can move metersized rocks. This implies that the dissipation of the nebula will remove meter-sized chunks of rock from the Solar System. Clearly the present bodies in the Solar System must have accreted to at least that size while the nebula was still present. But how rapid could accretion... | {
"Header 1": "Accretion of Rocks, Planetesimals, and Planets",
"token_count": 2033,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
It should be noted that these wind speeds are markedly subsonic.
We do not presently know to what size bodies could grow while the nebula was still present, but it seems likely that, over a time scale of about 10<sup>4</sup> years, much of the mass accreted into bodies with sizes of meters to kilometers. If bodies wi... | {
"Header 1": "Accretion of Rocks, Planetesimals, and Planets",
"token_count": 2043,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
In addition to the damping effect of this opacity, there is another constraint imposed by the relative time scales of infall of the gas and emission of radiation. A speed of 10<sup>5</sup> cm s<sup>-1</sup> at high altitudes and a gas density of $10^{-8}$ g cm<sup>-3</sup> at these altitudes mean that the mass influx... | {
"Header 1": "Accretion of Rocks, Planetesimals, and Planets",
"token_count": 1466,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Like all good things, even the solar nebula came to an end. The events surrounding the ignition of the Sun may have been violent, because a slight overshoot in the collapse process may have caused a "hydrogen flash" analogous to the helium flash we encountered in our survey of stellar evolution. Whether or not such a h... | {
"Header 1": "The T Tauri Phase",
"token_count": 2015,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
A fraction (A) of the incident light will be reflected back into space, and the remainder will be absorbed and eventually reemitted as
thermal black body radiation from the entire surface of the body, $4\pi a^2$ . At steady state,
$$(1-A)(\pi a^2 L_{\odot}/4\pi r^2) = 4\pi \varepsilon a^2 \sigma T^4,$$
(IV.214)
... | {
"Header 1": "The T Tauri Phase",
"token_count": 690,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
When one considers the complexity of the thermal environment in the solar nebula, with gravitational energy being turned into heat by collapse; with infall of interstellar gas and dust; with condensation, sedimentation, and accretion of solids; with temperature structure and energy fluxes dependent on opacity, which va... | {
"Header 1": "Thermal History of the Early Solar System",
"token_count": 1258,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
#### Energy Production in the Sun
- IV.1 If a star's composition differed from that of the Sun only in that it contained absolutely no carbon, the star is not precluded from fusing hydrogen via both the pp chain and the catalytic carbon cycle. Explain why.
- IV.2 Suppose a detector containing a million gallons (call ... | {
"Header 1": "Exercises",
"token_count": 1624,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
IV.22 Explain clearly in words why several-micrometer iron particles provide far more thermal opacity than the same mass of iron distributed as either 0:1-m or 10-cm particles.
#### Thermal Structure of the Nebula
IV.23 The adiabatic temperature profile presented in Fig. IV.42 completely neglects radiative transpor... | {
"Header 1": "Exercises",
"Header 2": "Dust Opacity",
"token_count": 663,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The outer Solar System presents an astoundingly diverse panorama. The four giant planets subdivide naturally into two classes, Jovian and Uranian. The Jovian planets, Jupiter and Saturn, which are not very far from the composition of the Sun or of other Population I stars, together have more than 100 times the combined... | {
"Header 1": "Introduction",
"token_count": 916,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
There are several important sources of information regarding the internal composition, structure, and dynamics of the Jovian planets. Among these are the masses, radii, and densities of the planets; the oblateness of their disks; their rotation periods; their internal mass distributions (departure from spherical symmet... | {
"Header 1": "Interiors of Jupiter and Saturn: Data",
"token_count": 2019,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The flux of energy from the Sun at 1 AU, $1.98 \, \mathrm{cal} \, \mathrm{cm}^{-2} \, \mathrm{min}^{-1}$ , is called the solar constant, denoted $F_{\odot,\,\oplus}$ . In more useful units, the flux at distance r from the Sun is
$$F_{\odot,r} = 1.375 \times 10^6 / r(\text{AU})^2 \,\text{erg cm}^{-2} \,\text{s}^{-... | {
"Header 1": "Interiors of Jupiter and Saturn: Data",
"token_count": 1889,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
We shall begin the task of modeling Jupiter and Saturn by considering isothermal planetary structures at 0 K. This is of course a disastrously bad approximation for the portion of a planet that we can observe directly, but is useful in the deep interior, where the density is comparable to that of a solid.
The equatio... | {
"Header 1": "Isothermal Interior Models of Jupiter and Saturn",
"token_count": 2032,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
As the next step in this direction, let us now consider the results from calculations using equations of state for pure hydrogen at low temperatures. The radius of a cold pure-hydrogen planet as a function of its mass is shown in Fig. V.3. It can be seen that the largest cold hydrogen body that can be built has only ... | {
"Header 1": "Isothermal Interior Models of Jupiter and Saturn",
"token_count": 952,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
A necessary feature of any successful model of the Jovian planets is that it explain their observed thermal emission and account for the transport of heat from their deep interiors up to observable levels of their atmospheres. There are three possible mechanisms for transport of heat: radiation, conduction, and convect... | {
"Header 1": "Thermal Models of Jupiter and Saturn",
"token_count": 2037,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
It is possible that the heat is derived from the growth of the metallic hydrogen mantle, which is associated with slow shrinkage of the entire planet at a rate of 1 mm per year; indeed, these two mechanisms are in no sense mutually
exclusive or even competitive, either being a logical consequence of the other.
A ty... | {
"Header 1": "Thermal Models of Jupiter and Saturn",
"token_count": 326,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
We have known since the pioneering work of Rupert Wildt in the 1930s that hydrogen, methane, and ammonia are present in Jupiter's atmosphere. Since 1966, however, there have been enormous advances in spectroscopic instrumentation. These advances have greatly multiplied the number of known species and correspondingly en... | {
"Header 1": "The Atmospheres of Jupiter and Saturn: Observed Composition",
"token_count": 2003,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Their absence is a great help in that it places constraints on chemical models of the Jovian planets: a model not only must pass the test of explaining the abundances and altitude distribution of the observed species, but also must not predict abundances of other species in excess of their observational detection limit... | {
"Header 1": "The Atmospheres of Jupiter and Saturn: Observed Composition",
"token_count": 896,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Our approach shall be to describe the chemical behavior of solar material along a Jovian pressure–temperature profile. We have already seen that the structure of the lower atmosphere is adiabatic, and we need only fix some (P, T) point in order to calculate the entire adiabat from theory. This convectively mixed, adiab... | {
"Header 1": "Tropospheric Composition and Structure: Theory",
"token_count": 2011,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
When the pressure is not too high, v(P) is not much less than the 1-atm standard value, v(1), and we have
$$a = e^{-\nu(1)(P-1)/RT} = e^{\mu(P-1)/\rho RT}.$$
(V.19)
Thus we can see that materials with very low densities show nonideal behavior even at very modest pressures of a few bars. The best example of such a l... | {
"Header 1": "Tropospheric Composition and Structure: Theory",
"token_count": 2006,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The ratio reaches a minimum at $3220 \,\text{K}$ , at which $f(\text{CH}_4)/f(\text{CO}) = 1870$ , as can be seen by setting the derivative of Eq. (IV.26) equal
to zero and solving for T. Thus CO is never more abundant than roughly 1 ppm of the total gas pressure, but is close to this abundance over a very wide ran... | {
"Header 1": "Tropospheric Composition and Structure: Theory",
"token_count": 2025,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The work done to create a surface of area dA (the surface energy) is clearly just $w = -\gamma dA$ , where $\gamma$ is the surface tension in erg cm<sup>-2</sup>. Applying Eq. (V.18) to the vapor pressure of a droplet,
$$RT \ln a = RT \ln p_{\rm v}/p_{\rm v}^0 = v(P)\Delta P. \tag{V.18}$$
Imagine a droplet of ra... | {
"Header 1": "Tropospheric Composition and Structure: Theory",
"token_count": 1264,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Saturation of $H_2O$ occurs when the partial pressure of water vapor in the atmosphere is equal to the local vapor pressure of water or of $H_2O$ ice, whichever is lower. For the reaction
$$H_2O(s, 1) = H_2O(g)$$
(V.42)
166 V. The Major Planets
Figure V.11 Cloud structure deep i... | {
"Header 1": "Cloud Condensation in the NH<sub>3</sub>-H<sub>2</sub>O-H<sub>2</sub>S System",
"token_count": 2022,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
When water, H2O ice, and vapor coexist (the triple point), then $\Phi = 3$ and f = 0. This means that only a single set of values of temperatures and pressure can characterize the triple point, with no freedom for variation.
If we add an inert gas that does not react chemically with water, but that contributes to t... | {
"Header 1": "Cloud Condensation in the NH<sub>3</sub>-H<sub>2</sub>O-H<sub>2</sub>S System",
"token_count": 2014,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
V.14 shows that, at 85 C, a sample that contains a total of 27 mol% NH3 will, at equilibrium, consist of a mixture of pure H2O ice and an aqueous NH3 solution of concentration X(NH3) ¼ 0:32. By conservation of mass, we can see that the amounts of the two condensates are fully determined; the conservation equations for ... | {
"Header 1": "Cloud Condensation in the NH<sub>3</sub>-H<sub>2</sub>O-H<sub>2</sub>S System",
"token_count": 2050,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Then, because we know $P(NH_3)(T)$ , we can use either Eq. (V.57) or (V.60) to calculate $P(H_2O)(T)$ . This situation, in which two condensed coexisting phases in a two-component system give unique partial pressures of both gases for each temperature, is analogous to a vapor pressure equation for a single condensed ... | {
"Header 1": "Cloud Condensation in the NH<sub>3</sub>-H<sub>2</sub>O-H<sub>2</sub>S System",
"token_count": 2046,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Thus only a few kilometers above the water-droplet cloud base, the temperatures are low enough to freeze the droplets. Figure V.14 shows that the solid phase produced by freezing such dilute NH3 solutions must be pure H2O ice. (The concentration of dissolved H2S is several times less than the NH3 concentration and ca... | {
"Header 1": "Cloud Condensation in the NH<sub>3</sub>-H<sub>2</sub>O-H<sub>2</sub>S System",
"token_count": 2049,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Thus $f=C-\Phi+1=0$ . In other words, as long as liquid and solid coexist at P=1 atm, the temperature cannot change.
The heat of fusion of ice at 1 atm pressure, $\Delta H_{\rm m}^{\circ}$ , is just $-\Delta H_{\rm f}^{\circ}$ , the heat of freezing. In order to withdraw this amount of heat from the water and free... | {
"Header 1": "Cloud Condensation in the NH<sub>3</sub>-H<sub>2</sub>O-H<sub>2</sub>S System",
"token_count": 2034,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
\quad (V.88)$$
It is convenient to use the dimensionless energy variable Y ¼ f -/RT as a measure of the strength of the heat contribution from condensation:
$$(dT/dz)_S = -\mu g(1+Y)/C_p[1+RY^2/xC_p],$$
(V.89)
for H2O condensation near 280 K, Y 10<sup>3</sup> 104/(2 280) ¼ 0:018. At this temperature C<sup>p</sup>... | {
"Header 1": "Cloud Condensation in the NH<sub>3</sub>-H<sub>2</sub>O-H<sub>2</sub>S System",
"token_count": 2047,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Because of the lack of confirming data, only the principal features of these cloud models for Jupiter (temperature of the cloud base; general decrease of average cloud density with altitude) should be taken seriously.
Saturn may have similar features, but there are serious observational problems that make this questi... | {
"Header 1": "Cloud Condensation in the NH<sub>3</sub>-H<sub>2</sub>O-H<sub>2</sub>S System",
"token_count": 1935,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The Galileo Probe spacecraft was designed and instrumented to solve the fundamental compositional problems presented by the atmosphere and cloud layers. The Galileo mission fought extraordinary obstacles from the very start. Its launch was repeatedly delayed before 1986 by a host of problems. The spacecraft was finally... | {
"Header 1": "Galileo Perspectives on Jovian Clouds",
"token_count": 1533,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Even in the total absence of solid condensation nuclei, supersaturation can be avoided if ions are reasonably abundant. For example, water, with its large dipole moment, will readily form several layers of molecules about a single p or e charge. The ''cluster ion'' series H<sup>þ</sup>, H3O<sup>þ</sup>, H5O2 <sup>þ</su... | {
"Header 1": "Ion Production in the Jovian Atmosphere",
"token_count": 2045,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Figure V.22 shows the stopping depths of vertically incident protons of energies 0.1 to 100 MeV in a hydrogen-helium isothermal atmosphere at 110 K. It can
Figure V.22 Penetration of energetic protons into an isothermal hydrogen-helium atmosphere. Radiation-belt or cosmic-ray protons i... | {
"Header 1": "Ion Production in the Jovian Atmosphere",
"token_count": 2024,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Since a typical atom has a radius of about $2 \times 10^{-4} \,\mu\text{m}$ , a Mie-scattering particle must be about
184 V. The Major Planets
$2 \times 10^3$ atoms in diameter. For spherical particles, that is equivalent to about $4 \times 10^9$ atoms per particle.] Mie theory is tractable, however, given cert... | {
"Header 1": "Ion Production in the Jovian Atmosphere",
"token_count": 2026,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The presence of even small amounts of absorbing matter in the topmost cloud layer will cause strong local absorption of solar energy.
For the observational astronomer interested in selecting an appropriate optical model for the atmosphere to help interpret spectroscopic observations, the situation is unpleasantly com... | {
"Header 1": "Ion Production in the Jovian Atmosphere",
"token_count": 1951,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The visual appearance of Jupiter has for three centuries provided a fascinating and puzzling stream of observations. Rapid and extensive changes often take place, with areas larger than Earth sometimes changing markedly in color and morphology in a few days. Dayto-day changes are often visible, even though the practica... | {
"Header 1": "Horizontal Structure and Atmospheric Circulation",
"token_count": 1996,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Then we can write
$$P_0 + \Delta P = P(\rho_0 + \Delta \rho)$$
= $P(\rho_0) + \Delta \rho (dP/d\rho)$ , (V.120)
where we have expanded $\rho$ about $\rho_0$ . Then
$$K = \Delta P / \Delta \rho = (dP/d\rho)\rho_0, \qquad (V.121)$$
where the constant K is the proportionality constant between $\Delta P$ an... | {
"Header 1": "Horizontal Structure and Atmospheric Circulation",
"token_count": 2006,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
This complex of spots, called the South Tropical Disturbance (STD), caught up with the GRS in June of 1902, accelerated abruptly, and passed it by in 5 days, rather than the 42 days that would have been required before the spots accelerated. The STD survived this encounter, with a new period closer to that of the GRS, ... | {
"Header 1": "Horizontal Structure and Atmospheric Circulation",
"token_count": 2041,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
V.30. All fluxes given are averages over the entire planet.
We must now confront the problem of describing and explaining the motions of the Jovian atmosphere in terms of quantitative physics. In order to give a fair appreciation of the magnitude of this task, it is necessary to begin at a very elementary level and i... | {
"Header 1": "Horizontal Structure and Atmospheric Circulation",
"token_count": 1987,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The Major Planets
In the study of the motion of fluids it is often convenient to consider the vector $\overrightarrow{\nabla} \times \overrightarrow{v}$ , and we therefore introduce a quantity $\overrightarrow{\Omega} = \overrightarrow{\nabla} \times \overrightarrow{v}$ , called the *vorticity*. For some purposes, ... | {
"Header 1": "Horizontal Structure and Atmospheric Circulation",
"token_count": 2045,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The general equation for motion of the fluid then becomes
$$\rho \{ \partial \overrightarrow{v} / \partial t + (\overrightarrow{v} \cdot \overrightarrow{\nabla}) \overrightarrow{v} \}$$
$$= -\overrightarrow{\nabla} P - \rho \overrightarrow{\nabla} U + \eta \nabla^{2} \overrightarrow{v}$$
$$+ (\eta + \eta') \overr... | {
"Header 1": "Horizontal Structure and Atmospheric Circulation",
"token_count": 2044,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
In a steady-state flow situation (not necessarily steady flow), the horizontal pressure gradient forces and the Coriolis forces will be in balance. This condition is called geostrophic flow.
Previously, in discussing the nature of atmospheric motions near belt–zone boundaries, we mentioned that a dry adiabatic colu... | {
"Header 1": "Horizontal Structure and Atmospheric Circulation",
"token_count": 2026,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
This strongly suggests that the GRS is an active precipitating storm system of immense size and with an unusual degree of vertical turbulence. When we next examine the photochemistry of the Jovian atmosphere, these distinctions will be important. Figure V.31 compares two images of the Great Red Spot taken
![](_page_2... | {
"Header 1": "Horizontal Structure and Atmospheric Circulation",
"token_count": 1192,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
We have up to now paid attention to the propagation of both visible and infrared radiation in solar-composition atmospheres, but ignored the effects of ultraviolet radiation. This is not because the effects of UV light are unimportant, but rather because molecules are such strong absorbers of UV that very little of it ... | {
"Header 1": "Photochemistry and Aeronomy",
"token_count": 2022,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
The mean free path is just $1/n\sigma$ , where $\sigma$ is the collision cross-section (cm<sup>2</sup>) and n is the local density (cm<sup>-3</sup>). At the level at which the density is $10^{-8}$ amagat ( $10^{-8}$ times Loschmidt's number = $10^{-8} \times 2.689 \times 10^{-8}$
$10^{19} \, \mathrm{cm}^{-3}$ ... | {
"Header 1": "Photochemistry and Aeronomy",
"token_count": 1921,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Molecular hydrogen can be ionized by UV light with wavelength less than 804 Å (80.4 nm):
$$H_2 + hv \rightarrow H_2^+ + e^- - 15.6 \,\text{eV}$$
(V.178a)
$$\rightarrow H^+ + H + e^-.$$
(V.178b)
From Table V.2 we can see that the first ionization potential of helium is larger than that of $H_2$ , and hence an ele... | {
"Header 1": "Photochemistry and Aeronomy",
"token_count": 2026,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Other species, such as the ${\rm H}^-$ ion, are present in only negligible quantities.
Figure V.39 Upper atmosphere structure of Jupiter. Species are well mixed in the troposphere, having constant mole fractions except where certain species are depleted by condensation. No condensatio... | {
"Header 1": "Photochemistry and Aeronomy",
"token_count": 2031,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Local concentrations of biologically interesting (organic) compounds in the stratosphere near the 250 mb pressure level then reflect a vertical turbulentmixing speed of about $v_z = K/H = 10^3/3 \times 10^5 =$ 0.003 cm s<sup>-1</sup>. The mean steady-state downward flux of "heavy" hydrocarbons, estimated from the phot... | {
"Header 1": "Photochemistry and Aeronomy",
"token_count": 2017,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
As with NH3, the large flux of available photons at - > 1600 A˚ means rapid photolysis, hundreds of times faster than CH4 photolysis.
Because of similar molecular structure and stability, the photochemistry of PH3 is very similar to that of NH3,
$$PH_3 + hv \rightarrow PH_2 + H, \qquad (V.192)$$
and three-body re... | {
"Header 1": "Photochemistry and Aeronomy",
"token_count": 2043,
"source_pdf": "datasets/websources/Astronomy_v1/Astronomy/Lewis_2004.pdf"
} |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.