Author name code: wildt ADS astronomy entries on 2022-09-14 author:"Wildt, Rupert" ------------------------------------------------------------------------ Title: Spectra of Four Outer Planets Authors: Wildt, R. Bibcode: 1982SciAm.247...11W Altcode: No abstract at ADS Title: Physical properties of giant planets Authors: Wildt, R. Bibcode: 1974STIN...7518136W Altcode: The chemical identification and physical nature of giant planets are discussed. The phase equilibria of H2-He mixture is briefly described for these large planets. Title: Thermodynamics of the Gray Atmosphere.IV. Entropy Transfer and Production Authors: Wildt, Rupert Bibcode: 1972ApJ...174...69W Altcode: In strict radiative equilibrium, i.e., if heat transport by conduction and convection is negligible, the local rate of entropy production must equal the divergence of the net flux of radiant entropy. Verification that this divergence is positive for LTE, is straightforward even in the nongray case. Entropy production throughout the interior can, in the absence of mass ejection, be disposed of only by the flux of radiant entropy escaping at the stellar surface, to which there is an (unattainable) upper limit depending solely on the effective temperature, namely, the entropy loss from the surface of an isothermal blackbody radiating at the same temperature. In effect, irrespective of grayness, the steady-state global rate of entropy production is bounded. Title: Hydrogen planets and high-pressure physics Authors: Wildt, Rupert Bibcode: 1972PEPI....6....1W Altcode: No abstract at ADS Title: The outer planets: Some early history. Authors: Wildt, R. Bibcode: 1969JAtS...26..795W Altcode: No abstract at ADS Title: Yale University Observatory, New Haven, Connecticut. Report 1967-1968. Authors: Wildt, R. Bibcode: 1969BAAS....1..134W Altcode: No abstract at ADS Title: Etude Physique des Planètes et des Satellites (Physical Study of Planets and Satellites) Authors: Wildt, R. Bibcode: 1968IAUTB..13...94W Altcode: No abstract at ADS Title: Thermodynamics of the Gray Atmosphere. III. Entropy Defect and Source Function Authors: Wildt, Rupert Bibcode: 1966ApJ...146..418W Altcode: The total entropy of a pencil of non-equilibrium radiation falls short of the entropy maximum associated with equilibrium radiation of the same total energy as that of the pencil (entropy defect of nonequilibrium radiation). For the source function an entropy defect can likewise be defined, and its integral over the entire atmosphere, called "global entropy defect," affords a measure of the over-all departure from LTE. In a gray atmosphere, minimizing the global entropy defect of the source function, with proper constraints, generates the spectrum of a source function conforming to the non-degenerate case of Bose-Einstein statistics. It attains at the surface the maximum departure from a Planck function, to which it tends monotonically with increasing optical depth. A physical interpretation of Hopf's function q(r) is given in the Appendix. Title: Thermodynamics of the Gray Atmosphere. II. Unattainability of Detailed Balancing Authors: Wildt, Rupert Bibcode: 1966ApJ...143..363W Altcode: In a gray atmosphere in local thermodynamic equilibrium all pencils of radiation are bluer than equilibrium radiation of matching total energy; and the divergence of the net flux of photons is positive at all depths-to the effect that radiation transmitted suffers cumulative reddening and that the rates of inverse atomic processes of interaction between gray matter and off-equilibrium radiation cannot balance. The unattainability of detailed balancing conforms to principles of kinetics (Einstein relations, etc.) holding irrespective of grayness. While under non-gray conditions it would be difficult to ascertain the sign of the divergence of the photon net flux, a sufficient condition for its positivity in the gray case is the monotone approach to asymptotic thermodynamic equilibrium at great depth. Title: The greenhouse effect in a gray planetary atmosphere Authors: Wildt, Rupert Bibcode: 1966Icar....5...24W Altcode: Hopf's analytical solution is illustrated for several values of the greenhouse parameter, i.e., the ratio of gray absorption coefficients for insolating and escaping radiation, assumed to be constant at all depths. Title: Thermodynamics of the Gray Atmosphere. I. Reversible Adiabatic Processes. Authors: Wildt, Rupert Bibcode: 1964ApJ...140.1343W Altcode: For every pencil of radiation inside a gray atmosphere in strict radiative equilibrium, energy spectra characteristic of different net fluxes (effective temperatures) are linked by a certain similarity transformation if the source function, which need not be Planckian, undergoes the same transformation. Related transformations hold for the concomitant variations of the spectra of radiant entropy. The common physical correlates of these similarity laws are quasi-statical processes taking the radiation field of the gray atmosphere, a non-equilibrium system, from one steady state to another. Because they satisfy all appropriate criteria, it is well within the bounds of accepted usage to call them reversible adiabatic processes, a term that classical thermodynamics had reserved for passages through a sequence of equilibrium states. Title: The Atmosphere of Jupiter Authors: Wildt, R. Bibcode: 1964oeao.conf..304W Altcode: No abstract at ADS Title: Thermodynamics of the Gray Atmosphere. Authors: Wildt, Rupert Bibcode: 1963AJ.....68Q.547W Altcode: The classical problem in radiative transfer is to find the source function sustaining strict radiative equilibrium in a gray atmosphere. That restriction, owing to the linearity of the monochromatic transfer equation, has made it possible to detach study of the conservation of radiant energy from inquiry into its spectral composition. The latter commences with an appeal to Planck's generalization, for nonequilibrium radiation, of Wien's displacement law. For every pencil of radiation inside a gray atmosphere in strict radiative equilibrium, energy spectra characteristic of different effective temperatures (net fluxes) are linked by a certain similarity transformation, provided that the source function, which need not be Plauckian, undergoes the identical transformation; and vice versa. Analogous displacement laws hold for the concomitant changes in spectral distribution of radiant entropy and of the entropy source function. The physical correlate these similarity laws have in common are quasistatical processes that convey, by a finite change of the net flux, the radiation field of the gray atmosphere, i.e., a nonequilibrium system, from one steady state to another. Because they satisfy all appropriate criteria, it is well within the bounds of accepted usage to call them reversible adiabatic processes, a term reserved in classical thermodynamics for passage through a sequency of equilibrium states. The complete distribution, throughout a gray atmosphere, of the spectrum of the source function accrues from a tentative extremum principle replacing arguments from thermostatics. Minimization of the global entropy deficit of the source function (a quantity identically nought in LTE), under the constraints that strict radiative equilibrium is preserved at all levels and that the photon flux escaping at the surface remains invariant, yields the Kothari-Singh function. It differs from the Plauck function by an additive parameter related to the nonvanishing free enthalpy of nonequilibrium radiation. Since the new parameter varies proportional to the second exponential integral of the optical depth, LTE is reached asymptotically. This event dispos&s of a conjecture (Wildt, R., Astrophys. J. 123,115, 1956) which had left the march of the parameter undetermined. Title: Planetary Interiors; rapport introductif Authors: Wildt, R. Bibcode: 1963LIACo..11...15W Altcode: No abstract at ADS Title: The Gray Planetary Atmosphere. Authors: Wildt, Rupert Bibcode: 1961AJ.....66S.298W Altcode: The problem of strict radiative equilibrium in a gray planetary atmosphere of infinite depth was formulated by Milne (1922) as an inhomogeneous integral equation. Its solution (Hopf 1934) can be expressed in terms of Chandrasekhar's H function and an integral over Hopf's q function. The temperature distribution, as function of the optical depth below the surface, has been evaluated numerically for several values of the angle of incidence of the insolating flux. Hopf's analytical solution also holds, after application of certain scale factors, for the temperature distribution in an atmosphere whose gray absorption coefficient for the incident solar radiation differs from that for the (infrared) planetary radiation, the ratio of the two coefficients being constant throughout the atmosphere. Even this generalization affords but a poor model of the familiar planetary atmospheres in their present state. Nevertheless, it deserves to be known more widely; for it is, to date, the only problem in planetary radiative equilibrium that has been solved rigorously. Title: Planetary Interiors Authors: Wildt, Rupert Bibcode: 1961plsa.book..159W Altcode: No abstract at ADS Title: Molecules and Late-Type Stellar Models. Authors: Vardya, M. S.; Wildt, Rupert Bibcode: 1960ApJ...131..448V Altcode: A difficulty encountered by Osterbrock, when he tried to identify particular red dwarf stars by interpolating between his models of late-type maIn-sequence stars, is shown to be alleviated by including the effects produced by hydrogen molecules in the convective zone. Title: A search for airborne particles of meteoritic origin Authors: Hodge, P. W.; Wildt, R. Bibcode: 1958GeCoA..14..126H Altcode: A year-long programme involving daily collections of atmospheric dust at several widely separated, isolated sites has been undertaken with the object of identifying particles that may be of extraterrestrial origin. The particles in question are opaque, shiny spherules with diameters less than 15 μ. They appear to be of a nature entirely different from that of the larger spheres abounding in densely populated areas. Their meteoritic origin is suggested by recent evidence regarding ablation of meteorites and by the fact that the rate of fall and the frequency distribution with size of these particles have been found to be the same at the various stations. The average rate of fall for each station was 1·1 spherules greater than 3 μ in diameter/cm 2/day. Assuming that the density of the counted particles is that of magnetite, this rate corresponds to an annual accretion for the entire earth of about 5 × 10 8 kg of these particles. Title: Inside the Planets Authors: Wildt, Rupert Bibcode: 1958PASP...70..237W Altcode: No abstract at ADS Title: Molecules in Stars: Theoretical Aspects. Introductory Report. Authors: Wildt, Rupert Bibcode: 1957LIACo...7..319W Altcode: No abstract at ADS Title: Radiative Transfer and Thermodynamics. Authors: Wildt, Rupert Bibcode: 1956ApJ...123..107W Altcode: The irreversibility of radiative transfer is made manifest by analyzing the steady-state interaction of the nonisotropic field of nonequilibrium radiation with an isotropic atom gas. It is shown that the practice of substituting the Planck function for the source function contravenes the second law of thermodynamics. Consideration of the nonequilibrium entropy leads to rather general conjectures regarding the spectral distribution of the source function. Title: On the Difference in Chemical Composition Between - and Low-Velocity Stars. Authors: Schwarzschild, M.; Spitzer, L., Jr.; Wildt, R. Bibcode: 1951ApJ...114..398S Altcode: The spectroscopic peculiarities of highwelocity of the CH bands and weakening of the CN bands and of the metal lines-can tentatively be explained by a general reduction in the abundance of the heavy elements and a somewhat lesser reduction in the abundance of the medium-heavy elements, relative to the abundances for low-velocity stars. As a working hypoQhesis, it is proposed that such a general difference in chemical composition between stars of populations I and II stems from the preferential accumulation of grains in the denser interstellar clouds from which the star of population I might be formed. The astrophysical discussion indicates that the dissociation energy of the molecules N2 and CO should be close to 9.5 e.v.; the considerably lower or higher values still advocated by some spectroscopists are not supported by the astronomical evidence. Title: New emission lines in M dwarfs. Authors: Wildt, Rupert Bibcode: 1951AJ.....56S..51W Altcode: 1951AJ.....56...51W A number of ultraviolet spectra of K and M dwarfs were obtained with the Qf/2 camera, dispersion about 65A/mm at X325o, attached to the spectrograph of the 8 -inch McDonald reflector. The exposure times were chosen as long as feasible, in order to record the ultraviolet at wave lengths less than X35oo. A cursory inspection of the first exposure of the star BD 2002465 (dM4e) revealed 3 emission lines below X33oo, where the continuum of the star had already faded out; their existence was confirmed by a second exposure. Bright lines of HI and CaiI had been noticed in this star by Swings and Struve,1 and recently it has become famous as a flare-star.2 No photoelectric magnitudes were recorded at Lick during the nights the spectrograms were taken at McDonald, 1950 February 5, 8:oI U.T. and February 7, 6:56 U.T. Since Swings and Struve had stressed the similarity of the emission spectra of BD 2002465 and YY Gem, this star too was examined for emissions in the far untraviolet. Only one spectrogram with an exposure time of 6 hours is available. It shows the continuum extending to about 3250, making it more difficult to disentangle faint emission lines. Omitting two doubtful ones, 6 emission lines were recognized in BD 2002465 and 4 of these also appear in YY Gem. However, their character is quite different in these two stars. In BD 2002465 the emission lines stand out 556 1/2 5.56 3/2 13/2,2 4.63 5.53 7/53/2 z4D0 4.62 549 z6D0 5/2 4.60 7/2 ~4175 9/2 i5 1.69 Figure. 1/32/ 1.09 1.66 ~3/29 4 2 1.07 a4D 3/71/3 1.04 0.96 Fell emissions in M dwarfs. lines observed in BD +20e2465, Q lines observed in VY Gem (Castor C). sharply against the background fog, and there is no doubt about their nature as "lines"; an exception is the rather diffuse emission at X3228 where there is some vignetting by the spectrograph. In YY Gem the emissions are quite diffuse. In particular, X3256 looks nearly 2A wide; and X3278 appears unsymmetrical, the continuous background being of different density to the red and ultraviolet of this line, as if the emission line coincided with the edge of an absorption band degraded toward th ultraviolet. It is fair to say that the existence of these emissions in YY Gem could hardly have been established from a single spectrogram if it had not been for for their previous discovery in BD 2002465. All the lines were identified with the strongest members of two low-excitation multiplets in the spectrum of Fell; they are entered in the term diagram shown in the figure, which also contains the appropriate excitation potentials. The same two multiplets of Feii, including their fainter members, appear in emission in a Herculis (M ) and a Scorpii (MI), according to G. Herzberg's observations.1 He proved that Feii emission does not originate in the atmospheres of the early-type companions of these stars, but is characteristic of the giants themselves, which also have bright H and K lines. Herzberg also lists 8 unidentified emissions; one of them, at X329o.I5, may be identical with a doubtful emission at X3290.o in BD 2002465. Both a Herculis and a Scorpii have also bright H and K lines. Thus there is suggested remarkable parallelism in emission characteristics between dwarfs and supergiants of spectral type M. Further investiagtion of this point seems 1n- dicated. This investigation was supported by the Office of Naval Research. I.Pub. A.S.P. 53, 244, 1941. 2.K. C. Gordon and G. E. Kron, Pub. A.S.P. 6i, 210, 1949. 3.Ap. J. 107, 94, 1948. Yale University Observatory, New Haven, Conn. Title: Continuous absorption by interstellar molecules. Authors: Wildt, Rupert Bibcode: 1949AJ.....54..139W Altcode: Certain diatomic molecules possibly quite common in interstellar space deserve attention for their continuous absorption, although such spectra are not strong enough to affect interstellar absorption, as the term is understood in relation to the apparent magnitude of distant stars. However, the photodissociation resulting from such molecular absorption might be important among the processes by which the radiant energy of interstellar space is brought into interaction with the kinetic energy of its gaseous population. The relevance of continuous molecular absorption to the problem of the kinetic temperature of interstellar matter was recognized by L. Spitzer, Jr.1 This note deals mainly with two interesting hydrogen spectra not mentioned by Spitzer. Both ionized and neutral hydrogen molecules have continuous absorption spectra between XI 000 and X3000, involving the following transitions: H2+(Is(rI~5t) hvHH2+(2~cr2~ffi) HII(Is2S) H~ and H(Is2S) H(Is2S) HH2(Is(r2p~1~0~) hPHH2(IsJ2sJ1~0+). The first spectrum is the dissociation continuum of the ground state of H2+. The second spectrum is an association continuum: two colliding hydrogen atoms in their ground states, provided their electronic spins are parallel, constitute an unstable molecular state which can be transformed into a stable excited state by absorption of a suitable photon. Both spectra are of great intrinsic strength, the f-value summed over all frequencies being nearly I for H1~ and probably between I and 2 for H2. Hence H2+ is highly susceptible to decomposition even in the H I regions of interstellar space, since it is not protected against photodissociation by the Lyman continuum of atomic hydrogen. Formation of H2+ occurs by collision between H and H~, followed by emission of a photon: this is one of the rare cases in which recombination into the ground state by double collision is permitted under the electronic transition rules. Recombination of two hydrogen atoms into the ground state of H2 is feasible only by a triple collision and, therefore, must be quite exceptional in interstellar space. On the other hand, H2 in its singlet ground state is well shielded against photodissociation and photoionization by the Lyman continuum, as Spitzer pointed out. Because triplet-singlet transitions are forbidden in such light molecules as H2, the excited triplet molecules originating from photoassociation must have a very short life-time, decomposing spontaneously via the lowest (unstable) triplet state. Considered genetically, the hydrogen molecules of interstellar space fall into two classes, vlz. singlet molecules, which may be rare, but should be stable, and triplet molecules, which should be common ~n H I regions, though rather short- lived. The optimum rate of formation of H2+ is obtained if protons and hydrogen atoms are present in amounts of the same order of magnitude. Hence the existence of H2~ is practically restricted to the narrow transition zones between the H II and H I regions of interstellar space, and consequently the formation and decay of H2+ should not be of great importance in evaluating the kinetic temperature of the bulk of interstellar matter. Further discussion of the H2+-effect must await completion of the work on the c4ntinuous absorption coefficient of this molecule, ~vhich is now being undertaken by Prof. Massey and Dr. Buckingham. Transition probabilities and mean life-times for the four lowest vibrational states of the I~g+ level of H2 have been derived by A. S. Coolidge, H. James and R. D. Present.2 A naive application of the Franck-Condon principle would lead to the expectation that a marked transfer of energy from the interstellar radiation field (by the association continuum) to the kinetic energy of the hydrogen gas (by the spontaneous dissociation of the excited triplet molecules) could take place, because absorption of photons would occur on the average at greater nuclear distances (consuming photons of higher frequencies) than re-emission (generating photons of lower frequencies). But the rigorous analysis of Coolidge, James and Present indicates that re-emission from the excited vibrational states occurs predominantly from the outer part of the potential curve, thus producing again high-frequency radiation and low kinetic energy of the receding atoms. Loss and gain of the kinetic energy of the atomic hydrogen appear largely to cancel, and qualitatively one must conclude that the transitory existence of the triplet molecules does not appreciably raise the kinetic temperature of the hydrogen gas. A quantitative test of this surmise would demand laborious numerical integrations for various sets of assumed kinetic temperatures and energy curves of interstellar radiation. It would also be necessary to extend the work of Coolidge, James and Present to the transition probabilities for the higher vibrational states, which are reached by absorption of interstellar radiation of wave lengths shorter than 2000. Another hypothetical constituent of the H II regions are HeH+ molecules, which could be formed by collisions between protons and unexcited helium atoms. According to quantum mechanical computations these molecules have a stable ground state with a dissociation energy of I. I volt,3 and in fact they have frequently been observed in the mass spectrograph. By capture of an electron HeH+ would dissociate, as the ground state of the neutral helium hydride is unstable. No spectrum of HeH+ has so far been observed in the laboratory, and little is known about the theoretical energy level diagram. I.A~. J. 107, 6, 1948. 2.Phys. Rev. 55, 184, 1939. 3.S. Toh, Proc. Phys. Math. Soc. Japan 22, 119, 1940. Yale University Observatory,s1;0;537]New Haven, Conn. Title: On the Absorption Continuum of the Negative Oxygen Ion Authors: Wildt, Rupert; Chandrasekhar, S. Bibcode: 1947PMcCO...9..145W Altcode: No abstract at ADS Title: The Constitution of the planets (Council Report on the progress of astronomy) Authors: Wildt, R. Bibcode: 1947MNRAS.107...84W Altcode: No abstract at ADS Title: An Interpretation of the Heights of Lines in the Solar Chromosphere. Authors: Wildt, Rupert Bibcode: 1947ApJ...105...36W Altcode: General theory-The heights of different emission lines in the chromosphere, estimated from slitless flash spectrograms taken on a stationaryplate, depend on the total number of emitting atoms contained in a column along the line of sight, on the threshold sensitivity of the photographic emulsion, and on the transparency of the earth's atmosphere and of the optical system. Theoretical intensitis of a group of related lines originating from the same element are plotted against the estimated heights, H, and this plot is represented by a continuous function, E(H). The transformation of E(H) into the spatial density of the emitting atoms would be a straight problem of geometry if it were not for the interference of two physical effects introduced by the process of observation. First, the extra-terrestrial surface brightness of the chromosphere is distorted by atmospheric scintilla- tion,which produces a tremor disk around every surface element of the chromosophere as it appears in pro- jection. Second, since during the photographic exposure the moon covers, or uncovers, part of the lower chromosphere, the light emitted at different levels is recorded with different exposure times; and, for lack of optical resolving-power, the chromospheric crescents portrayed on a flash spectrogram are an aggregate of superimposed images taken with varying exposure times. The correction of the observed function E(H), obtained with a finite exposure time, to an infinitesimally short exposure, as it were, requires the solution of a certain integral equation, which can be effected simply by refrated differentia- tion. The resulting function,f(H), can then be freed from the distortion by scintillation, which proves to be numerically insignificant. This procedure has been applied to the comprehensive list of heights of flash lines estimated by S. A. MitcJiell. Density gradients-The radial decay of the density of hydrogen in the chromosphere is strictly expo- nential up to heights of the order of 15,000 km, numerically proportional to exp (-0.92 X 10-8 cm' H); the density gradients derived from the Balmer and the Paschen series are in good agreement. The same density gradient of hydrogen results from a comparison of the electron density at the base of the çhromo- sphere with that at the elevation of 15,000 km, deduced by Baumbach from the absolute intensity of the continuous spectrum of the solar corona, because the free electrons are nearly all produced by the ionization of hydrogen, by far the most abundant element in the solar atmosphere. The density laws of the metals can be represented as a sum of two or three exponentials. At heights less than 2000 km, their gradients are much steeper than that of hydrogen: but between 3000 and 6000 km they seem to approach the hydrogen gradient. The density gradients of Fe i and Fe ii are compatible with the existence of ionization equilibrium with constant temperature throughout the chromosphere. Excitation temperatures for Fe i and Ti ii are of the order of 30000_40000 K and increase with increasing excitation potentials. The density gradient of He i between 2000 and 6000 km is about one-quarter of that of hydrogen; the observations do not yield any confirmation of the density maximum of He i below the 2000 km claimed by other investigators. A bsolute densities.-On the Teller-Inglis theory, the quantum number (n = 40) of the last resolved member of the Paschen series implies an electron pressure of 0.11 dynes/cm-2 at the level H = 500 km. From this figure the partial pressure of hydrogen can be found if the abundance ratio, A, of hydrogen to all the electron-producing metals is known. Relative abundances of Na, Mg, Al, Ca, Fe, Cu, and Sr in the chromosphere are derived from the estimated heights and from absolute transition probabilities; these ratios agree quite well with those found by Russell from the Fraunhofer spectrum. While the chromosphere appears to be well mixed as regards the metals, the abundance ratio, A, of hydrogen to the sum of the metals increases greatly with height. This variation of A is evaluated by a comparison of lines of Fe i and the Balmer series; and the extrapolated value of A at the base of the chromosphere agrees as to order of magnitude with that re- sulting from B. Stromgren's model of the solar photosphere. The numbers of atoms per cubic centimeter at the level H = 500 km are: log CH = + 15.63 for neutral hydrogen, and log CFe = +9.53 for neutral iron Title: An Interpretation of the Heights of Lines in the Solar Chromosphere Authors: Wildt, Rupert Bibcode: 1947PMcCO...9..249W Altcode: No abstract at ADS Title: Ultra-violet spectra of R stars Authors: Wildt, Rupert Bibcode: 1946PAAS...10R.150W Altcode: No abstract at ADS Title: Theoretical color temperatures of hydrogen atmospheres Authors: Wildt, Rupert Bibcode: 1946PAAS...10S..71W Altcode: No abstract at ADS Title: On the Absorption Continuum of the Negative Oxygen Ion. Authors: Wildt, Rupert; Chandrasekhar, S. Bibcode: 1944ApJ...100...87W Altcode: A new determination of the electron affinity of oxygen (3.07 e.v.) suggests that the ionization contin- uum of 0 in the photographic ultraviolet region becomes so strong in late K and M stars that its con- tribution to the monochromatic absorption coefficient cannot be neglected. The influence of 0 on the Rosseland mean is insignificant. A discontinuity in the spectra of M giants, first observed by Lindblad, is tentatively identified with the absorption edge of 0-near X 4050. The theoretical strength of the Lind- blad discontinuity depends on the abundance ratio of atomic oxygen to atomic hydrogen, which in M stars varies with the pressure-sensitive shift of the dissociation equilibrium of the several hydrides and oxides. The result is a positive absolute magnitude effect for the Lindblad discontinuity. The differential of free-oxygen abundance implied by Lindblad's spectrophotometric observations agrees as to order of magnitude with that predicted by Russell from the dissociation equilibrium in giant and dwarf stars of the oxygen branch Title: On the Chemistry of the Atmosphere of Venus. Authors: Wildt, Rupert Bibcode: 1942ApJ....96..312W Altcode: Unpublished data by J. F. Walker show that the clouds of Venus cannot be composed of solid poiy- oxymethylene hydrates. Since the clouds cannot consist of water, it is suggested that a small deficiency in the aqueous component of the primordial magma of Venus may have prevented the formation of a hydro- sphere; i.e., all water may have been bound in hydrated minerals Title: The theory of continuous stellar spectra Authors: Wildt, R. Bibcode: 1942Obs....64..195W Altcode: No abstract at ADS Title: The Geochemistry of the Atmosphere and the Constitution of the Terrestrial Planets Authors: Wildt, R. Bibcode: 1942RvMP...14..151W Altcode: No abstract at ADS Title: The Absorption Coefficient of the Free-Free Transitions of the Negative Hydrogen Ion. Authors: Wheeler, John A.; Wildt, Rupert Bibcode: 1942ApJ....95..281W Altcode: The absorption coefficients pertaining to the free-free transitions of H are evaluated throughout the visual range and the entire infrared, on the basis of an approximate calculation, and are utilized for the determination of the Rosseland mean of the mass absorption coefficient of H (sum of free-free and bound-free transitions) in the low-temperature range (o.8 < 5o4o/T < 2.0). These data set a lower limit to the opacity of late-type stellar atmospheres, pending the discovery of further absorption mechanisms likely to become relevant in the low-temperature range Title: The Resonance Bands of the NH Molecule in Spectra of Class R. Authors: Wildt, Rupert Bibcode: 1941ApJ....93..502W Altcode: The ultraviolet resonance bands of NH have been identified in the spectra of R-type stars, photo- graphed at the McDonald Observatory with dispersions of 120 A/mm and 6o A/mm. The intensities of these bands have been compared with those of C2, CN, and CH. The large scattering of these intensities suggests considerable differences in the relative abundances of H, C, and N Title: The Continuous Spectrum of Stellar Atmospheres Consisting Only of Atoms and Negative Ions of Hydrogen. Authors: Wildt, Rupert Bibcode: 1941ApJ....93...47W Altcode: Theoretical color temperatures have been derived for stellar atmospheres consisting only of H and H in ionization equffibrium, over the range of effective temperatures 5o4o/T~ = 0.5-1.2 and for differ- ent electron pressures. Choosing the electron pressure so as to reproduce the value of the Ba]mer dis- continuity observed by Barbier and Chalonge, the color temperatures of the spectral types Ao-Fo determined by the same authors can be tolerably well represented by the H-H mixture. For the later spectral types the theoretical color temperatures fall considerably below the corresponding effective temperatures, while the observed color temperatures are distinctly higher than the effective ones. It does not seem possible to remove this discrepancy by adding the conventional metaffic absorption to that of H and H Title: On the Possible Existence of Formaldehyde in the Atmosphere of Venus. Authors: Wildt, Rupert Bibcode: 1940ApJ....92..247W Altcode: Ultraviolet spectrograms of Venus, and of the moon for comparison, were obtained with the long-focus quartz spectrograph (dispersion 21.7 A/mm at A 3300) attached to the 82-inch reflector of the McDonald Observatory, in order to search for the electronic absorption spectrum of formaldehyde gas, which might be formed in Venus' atmosphere by photochemical synthesis. The spectrograms revealed no sign of absorption by CH2O, while a mass of this gas equivalent to 3 mm-atm, under standard conditions, should have been sufficient for spectroscopic identification. This negative result does not refute the assumption that the photochemical formation of CH2O has played an important role in Venus' atmosphere during the past. In the light of Tarnmann's theory of the origin of the terrestrial oxygen, the lack of oxygen on Venus indicates that the primordial atmos- phere of this planet must have been extremely poor in water vapor. A tenuous atmos- phere of water vapor and carbon dioxide affords the very conditions for the photochemi- cal synthesis of formaldehyde, which appears to be capable of proceeding until the sup- ply of either of these gases has been exhausted. In a moist atmosphere CH2O rapidily polymerizes into a mixture of polyoxymethylene hydrates, (CH2O)~ H20, a white crystaffine solid. From laboratory data it is concluded that the amount of gaseous CH2O existing in equilibrium with the solid polymers is exceedingly small, which would seem to account for the failure of the spectroscopic test. The vapor tension of the solid polymers in the presumable range of Venus' atmospheric temperature is high enough to permit the dissolution and formation of clouds by processes of sublimation and sub- sequent condensation. As Venus' atmosphere is now spectroscopically free from water vapor but is obviously filled with clouds, the nature of which has never been settled, it is tentatively suggested that solid polyoxymethylene hydrates constitute the clouds shrouding the planet's surface Title: Note on the Surface Temperature of Venus. Authors: Wildt, Rupert Bibcode: 1940ApJ....91..266W Altcode: No abstract at ADS Title: Negative Ions of Hydrogen and the Opacity of Stellar Atmospheres. Authors: Wildt, Rupert Bibcode: 1939ApJ....90..611W Altcode: Compared to the current theory of the atmospheric absorption coefficient, the photo- spheric level is raised considerably in all spectral types later than F5 by including the contribution to the opacity made by the negative ions of hydrogen. Likewise, the dis- continuity at the Balmer limit is greatly reduced, so the values of this quantity ob- served in F stars can be represented without the assumption, advocated by Unsold, of an abundance ratio of hydrogen to metals equal to 50: I. The abundance ratio adopted by Russell and Pamiekoek (H : M = boo: i) appears to be compatible with the observa- tions of the Balmer discontinuity Title: On the chemical nature of the colouration of Jupiter's cloud forms Authors: Wildt, Rupert Bibcode: 1939MNRAS..99..616W Altcode: No abstract at ADS Title: Electron Affinity in Astrophysics. Authors: Wildt, Rupert Bibcode: 1939ApJ....89..295W Altcode: No abstract at ADS Title: Contribution to the opacity of stellar atmospheres by negative hydrogen ions Authors: Wildt, Rupert Bibcode: 1939PAAS....9R.236W Altcode: No abstract at ADS Title: On the state of matter in the interior of the planets Authors: Wildt, Rupert Bibcode: 1939PAAS....9Q.138W Altcode: No abstract at ADS Title: On the State of Matter in the Interior of the Planets Authors: Wildt, Rupert Bibcode: 1938ApJ....87..508W Altcode: The bulk of mass in the interior of the planets is in the ordinary condensed state. Only in the central parts of Jupiter and Saturn may there be matter in a state approach- ing the degenerate one. This is concluded from the central pressures of the terrestrial planets, as evaluated by Jeifreys, and from the internal pressures of the giant planets, which are computed here for a model consisting of a core similar in structure to the terrestrial planets, covered by a layer of ice and a layer of solid hydrogen on top of it. In this hydrogen layer the conditions are realized under which hydrogen should change to a metaffic modification predicted by theory. The condensation of ice VII from the primeval atmosphere must have started long before the temperature had dropped to the critical one, and probably was finished before the critical point was reached, which would imply that there never was on the giant planets an ocean of a depth comparable to the total mass of H20 present Title: Photochemistry of Planetary Atmospheres Authors: Wildt, Rupert Bibcode: 1937ApJ....86..321W Altcode: All polyatomic molecules detected in planetary atmospheres are highly sensitive to ultraviolet solar radiation. Their photochemical decomposition must be followed by secondary chemical reactions, reuniting the products of dissociation, in order to main- tain the observed stationary composition of the atmospheres. The stability of methane and carbon dioxide is reasonably accounted for, but that of ammonia remains unex- plained at present. The existence of methane and the failure to detect any other hydro- carbon indicate the presence of plenty of hydrogen on the giant planets, and most probably there is no carbon monoxide, carbon dioxide, or hydrogen sulphide at their surfaces. Small amounts of sundry molecules, not observed so far, are certain to be formed in consequence of the photochemical processes, and eventually these compounds may be detected under favorable circumstances Title: Note on stellar ionization and electric fields Authors: Wildt, Rupert Bibcode: 1937MNRAS..97..225W Altcode: No abstract at ADS Title: Low-Dispersion Spectra of Red Stars Authors: Wildt, Rupert Bibcode: 1936ApJ....84..303W Altcode: Over the range from A 3000 to X 9000 (total dispersion 3 mm approximately) the spectra of selected late-type stars have been compared. M giants and N stars are marked by a continuous absorption of wave-lengths shorter than X 4000, the amount being of the order o~'5 and 2~5, respectively. Types S and gM cannot be distinguished on low-dispersion spectrograms. Dwarfs of class M have a strong ultra-violet spectrum and R stars a fairly strong one. Various absorption bands are found in the far ultra- violet and are attributed tentatively to CN, CH, NH, OH, CaH. The classes R and N are possibly to be regarded as forming separate, parallel branches. The hypothetical physical processes causing the continuous ultra-violet absorption in gM and N stars are discussed. Title: Equilibrium of Stellar Atmospheres Under a Temperature Gradient Authors: Wildt, Rupert Bibcode: 1936ApJ....83..202W Altcode: If the temperature gradient maintained by the radiation flux is smaller than the adiabatic gradient of the stellar matter and, therefore, is not sufficient to set up con- vection currents, the constituents of the atmosphere will be separated partially by diffusion. For all constituents participating in processes of dissociation or ionization there are remarkable deviations from the well-known exponential distribution of the partial pressures (depending only on the molecular weight), the additional terms con- taming the space derivatives of the thermodynamical equilibrium constants. The kinetic equivalents to these terms are stationary diffusion currents, which transport reaction energy and increase the heat conductivity, although there is no net flux of mass. This diffusion equilibrium may be realized in the atmospheres of early B stars and of stars between the types G~ and M, which ought to be free from convection Title: No. 538. Equilibrium of stellar atmospheres under a temperature gradient. Authors: Wildt, Rupert. Bibcode: 1936CMWCI.538....1W Altcode: 1936QB4.M93n538.... No abstract at ADS Title: No. 551. Low-dispersion spectra of red stars. Authors: Wildt, Rupert. Bibcode: 1936CMWCI.551....1W Altcode: 1936QB4.M93n551.... No abstract at ADS Title: Dissociation and Ionization Equilibria in Stellar Atmospheres Authors: Wildt, Rupert Bibcode: 1935PASP...47..227W Altcode: No abstract at ADS Title: The Atmospheres of the Giant Planets Authors: Wildt, R. Bibcode: 1934Natur.134..418W Altcode: IN their article on the atmospheres of the giant planets1 Drs. A. Adel and V. M. Slipher suggest that a predominantly hydrocarbon structure might not be at all unlikely for these planets; this conclusion is also indicated, in their opinion, by the fact that the mean densities of these celestial bodies are in a class with densities of most organic liquids. Title: Über die stellare Dissoziation des Wasserstoffmoleküls. (Veröffentlichungen der Universitäts-Sternwarte Göttingen, Nr. 42. ) Mit 1 Abbildung. Authors: Wildt, Rupert Bibcode: 1934ZA......9..176W Altcode: No abstract at ADS Title: Über die stellare Dissoziation des Wasserstoffmolekuls Authors: Wildt, Rupert Bibcode: 1934VeGoe...3..208W Altcode: No abstract at ADS Title: Über den inneren Aufbau der grossen Planeten Authors: Wildt, Rupert Bibcode: 1933VeGoe...3..179W Altcode: No abstract at ADS Title: Kondensation in Sternatmosphären Authors: Wildt, Rupert Bibcode: 1933VeGoe...3...35W Altcode: No abstract at ADS Title: Ozon und Sauerstoff in den Planetenatmosphären Authors: Wildt, Rupert Bibcode: 1933VeGoe...3..151W Altcode: No abstract at ADS Title: Kondensation in Sternatmosphären. (Veröffentlichungen der Universitäts- Sternwarte Göttingen Nr. 33.) Mit 1 Abbildung. Authors: Wildt, Rupert Bibcode: 1933ZA......6..345W Altcode: No abstract at ADS Title: Über das ultrarote Spektrum des Planeten Saturn Authors: Wildt, Rupert Bibcode: 1932VeGoe...2..216W Altcode: No abstract at ADS Title: Absorptionsspektren und Atmosphären der gros;en Planeten Authors: Wildt, Rupert Bibcode: 1932VeGoe...2..171W Altcode: No abstract at ADS Title: Das Spektrum des Planeten Jupiter Authors: Wildt, Rupert; Meyer, E. J. Bibcode: 1931VeGoe...2..141W Altcode: No abstract at ADS Title: Das Spektrum des Planeten Jupiter. Mit 11 Abbildungen. (Eingegangen am 30. September 1931) Authors: Wildt, R.; Meyer, E. J. Bibcode: 1931ZA......3..354W Altcode: No abstract at ADS Title: Über Eigentümlichkeiten panchromatischer Platten Authors: Wildt, Rupert Bibcode: 1931VeGoe...2..157W Altcode: No abstract at ADS