Survival of the Earth and the future evolution of the Sun

The question of the survival of the planet Earth as the Sun becomes a red giant and possibly a planetary nebula depends on the maximum extent of the Sun's envelope. This study shows that if the Earth is reached by this envelope, it will be destroyed; but if it is not, it will survive. Present stellar evolution calculations imply that the Earth will be destroyed.     

Computation of the elements of eclipsing binary systems in the frequency-domain

The aim of the present paper will be to translate the essential parts of the theory of Fourier analysis of the light changes of eclipsing variables into more practical terms; and describe procedures (illustrated by numerical examples) which should enable their users to obtain the desired results with maximum accuracy and minimum loss of information by processes which can be fully automated.In order to unfold in steps how this can be done, the scope of the present paper-the first of two-will be restricted to an exposition of the analysis of light changes caused by eclipses of spherical stars; while between minima due to this cause the light of the system should remain sensibly constant. An extension of our analysis to incorporate photometric effects arising from mutual distortion of the components of close eclipsing systems between minima as well as within eclipses is being postponed for the second communication.In developing this subject we shall single out for the user's attention only those parts of the whole theory which are of direct relevance to practical work. Their justification can be largely found in sources already published; and new developments essential for our work, not yet made public, will be relegated to several Appendices at the end of the text, in order not to render its text too discursive and deflect the reader's attention from the main theme of its narrative.After a brief outline of the subject given in Section 1, Section 2 will introduce the reader to practical aspects of the Fourier analysis of the light curves; and Section 3 will be devoted to its use to determine the numerical values of the momentsA _2m of the light curves which constitute the cornerstones for all subsequent work. Section 4 will describe an algebraization of the process of determination of the elements for the case of total (annular) eclipses; while Section 5 will do the same for partial eclipses. The concluding Section 6 will be devoted to an error analysis of our problem, and to an outline of the way by which the errors of the individual observations will compound to the uncertainty of the final results. Lastly, Appendices 1–5 concluding the paper will contain additional details of some aspects of our work, or proofs of new processes made use of to obtain our results, whose earlier inclusion would have made the main text too discursive.     

Detecting the glint of starlight on the oceans of distant planets

We propose that astronomers will be eventually be able to discriminate between extrasolar Earth-like planets with surface oceans and those without using the shape of phase light curves in the visible and near-IR spectrum. We model the visible light curves of planets having Earth-like surfaces, seasons, and optically-thin atmospheres with idealized diffuse-scattering clouds. We show that planets partially covered by water will appear measurably brighter near crescent phase (relative to Lambertian planets) because of the efficient specular reflection (“glint”) of starlight incident on their surfaces at a highly oblique angle. Planets on orbits within 30° of edge-on orientation (50% of all planets) will show pronounced glint over a sizeable range of orbital longitudes, from quadrature to crescent, all outside the glare of their parent stars. Also, water-covered planets will appear darker than a Lambertian disk near full illumination. Finally, we show that planets with a mixed land/water surface will polarize the reflected signal by as much as 30-70%. These results suggest several new ways of directly identifying water on distant planets.     

Fourier analysis of the light curves of eclipsing variables,I

The aim of the present paper will be to pioneer a new approach to the analysis of the light changes of eclipsing binary systems in the frequency domain, and to point out its merits in comparison with a conventional treatment of the same problem in the time-domain which has been developed so far. Following an introductory section in which the broad features of our problem will be set forth, Section 2 will contain an outline, and critique, of the time-domain approach. Section 3 will give an explicit treatment of the light changes arising from total and annular eclipses in the frequency domain — a problem which we succeeded in solving in close algebraic form. Section 4 will extend this treatment to the case of partial eclipses; and in the concluding Section 5 the relative merits of our new results will be discussed in broader perspective. Sections 3 and 4 contain explicit results pertaining to mutual eclipses of spherical stars exhibiting uniformly bright discs. An extension of these results to the case of arbitrary limb-darkening, and taking account of mutual distortion of both components, will be given in subsequent communications.     

Normal galaxies in the all-sky survey by the eROSITA X-ray telescope of the Spectrum-X-Gamma observatory

We analyze the statistical properties of normal galaxies to be detected in the all-sky survey by the eROSITA X-ray telescope of the Spectrum-X-Gamma observatory. With the current configuration and parameters of the eROSITA telescope, the sensitivity of a 4-year-long all-sky survey will be ≈10^?14 erg s^?1 in the 0.5–2 keV band. This will allow ～(1.5–2) × 10⁴ normal galaxies with approximately the same contribution of star-forming and elliptical galaxies to be detected. All galaxies of the X-ray survey are expected to enter into the existing far-infrared (IRAS) or near-infrared (2MASS) catalogs; the sample of star-forming galaxies will be approximately equivalent in sensitivity to the sample of star-forming galaxies in the IRAS catalog of infrared sources. Thus, a large homogeneous sample of normal galaxies with measured X-ray, near-infrared, and far-infrared fluxes will be formed. About 90% of the galaxies in the survey are located within ～200–400 Mpc. A typical (most probable) galaxy will have a luminosity log L _X ～ 40.5–41.0, will be located at a distance of ～70–90 Mpc, and will be either a star-forming galaxy with a star formation rate of ～20M _⊙ yr^?1 whose X-ray emission is produced by ultraluminous X-ray sources (ULXs) or an elliptical galaxy with amass log M _* ～ 11.3 emitting through to a hot interstellar gas. The galaxies within 35 Mpc will collectively contain ～10² ULXs with luminosities log L _X > 40, ～80% of whichwill be the only luminous source in the galaxy. Thus, although the angular resolution of the eROSITA telescope is too low for the luminosity function of compact sources in galaxies to be studied in detail, the survey data will allow one to investigate its bright end and, possibly, to impose constraints on the maximum luminosity of ULXs.     

On the radio emission of Callisto

A model of an icy surface and interior for Callisto gives a predicted thermal radio emission in good agreement with experimental radio astronomical data. The radio brightness temperature of an icy surface will not depend on wavelength. This may be a method to test icy surface hypotheses. The brightness temperatures of other satellites with icy surfaces will be equal to 200–220°K and will not depend on wavelength.     

The effects of mutual irradiation on the observed radial velocity of the components of close binary systems

The aim of the present paper will be to investigate the effects, on the observed radial velocities of the components of close binary systems, of atmospheric motions caused by mutual irradiation of the two stars. Such motions can (and, in general, will) produce systematic differences between the observed radial velocity and that of the centre of mass of the respective star — differences varying with with the phase and thus giving rise to spurious deformations of the star's radial-velocity curves due to orbital motion. A failure to separate the two could (and in general, will) vitiate the physical elements deduced from these curves —such as the masses or absolute dimensions of the components and of the shape of their orbit; but in order to do so, an investigation of atmospheric motions invoked by irradiation becomes a necessary prerequisite.In the Introduction following this abstract, the problem at issue will be described in general terms, and phenomena outlined which should arise in this connection (together with the observations indicating their presence). In Section 2, general expressions for the radial velocity at any point of stellar surface arising from atmospheric motions will be formulated while Section 3 will isolate such velocities for components of close binary systems as are produced by mutual irradiation of their mates, in terms of hydrodynamical equations of radiative transfer describing the problem. In Sections 4 and 5, the effects of non-rotational motions on the observed radial velocities will be specified, and hydrodynamical equations formulated which specify atmospheric convection caused by irradiation of each component of a close binary by its mate. Linearized versions of such equations will be constructed in Section 6; while Section 7 contains an evaluation of the effects which such gas streams exert on the observed radial velocity of the stars.In the concluding Section 8 applications to practical cases are carried out. It will be shown that no reliable spectroscopic elements of close binary systems (including the masses and absolute dimensions of their components) can be obtained until the effects of atmospheric convection caused by mutual irradiation have been accounted for to permit us to convert the observed radial velocities (influenced as they are by the motion of as in which they originate) to those of the centre of mass of the respective stars.Paper dedicated to Professor Hannes Alfvén on the occasion of his 80th birthday, 30 May 1988.     

On the formation of void in the Universe

This paper deals with the void with a volume of ～10⁶ Mpc in the Universe. By using spherically-symmetric Einstein field equations the dynamics of void is studied. It seems to be possible that the void will decay in the radiation-dominated era so that the void will amplify and form in the matter-dominated era only.     

Recent advances in the long-wavelength radio physics of the Sun

Solar radio bursts at long wavelengths provide information on solar disturbances such as coronal mass ejections (CMEs) and shocks at the moment of their departure from the Sun. The radio bursts also provide information on the physical properties (density, temperature and magnetic field) of the medium that supports the propagation of the disturbances with a valuable cross-check from direct imaging of the quiet outer corona. The primary objective of this paper is to review some of the past results and highlight recent results obtained from long-wavelength observations. In particular, the discussion will focus on radio phenomena occurring in the outer corona and beyond in relation to those observed in white light. Radio emission from nonthermal electrons confined to closed and open magnetic structures and in large-scale shock fronts will be discussed with particular emphasis on its relevance to solar eruptions. Solar cycle variation of the occurrence rate of shock-related radio bursts will be discussed in comparison with that of interplanetary shocks and solar proton events. Finally, case studies describing the newly-discovered radio signatures of interacting CMEs will be presented.     

The Field Camera Unit of the WSO/UV telescope

The WSO-UV space observatory, an UV-optimized 1.7 m Ritchey-Chretien telescope, will investigate many astrophysical phenomena from planetary science to cosmology. The Field Camera Unit is a multi-spectral radial instrument on the focal plane of WSO-UV. It will have three channels covering the wide spectral range from 115 nm to 800 nm and it will be operated in imaging, low-resolution spectroscopic, polarimetric and spectro-polarimetric modes. This paper will discuss and review the main characteristics and the present status of this instrument.     

Contribution to the ground-based follow-up of the Gaia space mission

The Gaia Space Mission [Mignard, F., 2005. The three-dimensional universe with Gaia. ESA/SP-576; Perryman, M., 2005. The three-dimensional universe with Gaia. ESA/SP-576] will observe several transient events as supernovae, microlensing, gamma ray bursts and new Solar System objects. The satellite, due to its scanning law, will detect these events but will not be able to monitor them. So, to take these events into consideration and to perform further studies it is necessary to follow them with Earth-based observations. These observations could be efficiently done by a ground-based network of well-equipped telescopes scattered in both hemispheres.Here we focus our attention at the new Solar System objects to be discovered and observed by the Gaia satellite [Mignard, F., 2002. Observations of Solar System objects by Gaia I. Detection of NEOS. Astron. Astrophys. 393, 727] mainly asteroids, NEOs and comets. A dedicated ground-based network of telescopes as proposed by Thuillot [2005. The three-dimensional universe with Gaia. ESA/SP-576] will allow to monitor those events, to avoid losing them and to perform a quick characterization of some physical properties which will be important for the identification of these objects in further measurements by Gaia.We present in this paper, the beginning of the organization of a Latin-American ground-based network of telescopes and observers joining several institutions in Argentina, Bolivia, Brazil and other Latin-American countries aiming to contribute to the follow-up of Gaia science alerts for Solar System objects.     

The Data Flow, from Observations to the Archive: Simulating the Case of TNG

The telescopes of the new generation allow an archive to be built as a section of data management; nevertheless, careful planning is needed and data handling needs to be designed together with the control system of the telescope itself, both for space-borne and for ground-based facilities. Simulations are essential to understand how observations will be archived, and to build and test an archiving system capable of dealing efficiently with the expected data flow.The TNG (Telescopio Nazionale Galileo) will be one of the first ground-based observing facilities where archiving of both technical and scientific data will be made directly at the telescope as a natural extension of the data handling chain. The results obtained testing the prototype implementation of the archive system at the TNG with a simulated data flow will be shown.     

Lander and scientific equipment for exploring of volatiles on the Moon

It is planned that the LUNA-GLOB spacecraft will deliver an orbiter and 14 landers to the Moon.The schematic diagram of the spacecraft flight to the Moon is shown in Fig. 1

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Fig. 1. Schematic diagram of the LUNA-GLOB SC flight to the Moon.

. The flight time is estimated at 4.5 days. Some 33 h before the spacecraft approaches the Moon a container with 10 small high-velocity penetrators (SHVP) will be separated from the spacecraft. It will continue the flight to the Moon autonomously. When the container is at a close distance to the Moon it will intensively rotate, and the penetrators will be separated from it. They will continue their flight to the Moon, and at a rate of 2.6 km⧸s, they will penetrate the surface.Then, two large penetrators (LP) will separate and continue the flight autonomously. In due time they will decelerate and penetrate the surface at a rate of 80–100 m⧸s.Finally, after leaving the satellite orbit the polar station (PS) will land to the South Polar Region at a rate of 80–100 m⧸s.All 12 penetrators, which will be dropped from the spacecraft, have seismometers. They are intended for the research into the internal structure of the Moon that is one of the main scientific objectives of the project. The (PS) accommodates a complex of instruments intended for the solution of another objective of the project: the search for volatiles.     

Standard candles from the Gaia perspective

The ESA Gaia mission will bring a new era to the domain of standard candles. Progresses in this domain will be achieved thanks to unprecedented astrometric precision, whole-sky coverage and the combination of photometric, spectrophotometric and spectroscopic measurements. The fundamental outcome of the mission will be the Gaia catalogue produced by the Gaia Data Analysis and Processing Consortium (DPAC), which will contain a variable source classification and specific properties for stars of specific variability types. We review what will be produced for Cepheids, RR Lyrae, Long Period Variable stars and eclipsing binaries.     

WSO and the winds of massive stars: the gate to the metal-poor Local Universe

The spectrographs on-board the World Space Observatory (WSO) will provide access to the 1020–1800 Å wavelength range with unprecedented sensitivity. Previous observatories operating in the 1150–2000 Å range (such as IUE and HST-STIS) have proved extremely useful to study the winds of OB type stars, which leave their most prominent imprints in the far ultraviolet range. The addition of the λ < 1200 Å wavelengths is critical as it contains important diagnostic lines for mass loss and shocks in the wind, as found by FUSE-based analyses.WSO will enable quantitative spectroscopic analyses of blue massive stars in the Local Group beyond the Magellanic Clouds. The results will lead to the characterization of their winds as a function of metallicity, and shed new light on current urging questions regarding radiation driven winds.     

Neutral corpuscular energy flux by charge-transfer collisions in the vicinity of the sun

Charge-transfer collisions between solar-wind protons and neutral interstellar hydrogen in the vicinity of the sun have been considered. Due to the focusing effect of the sun's gravitational field interstellar particles entering the solar system in free flights produce a specific density distribution in the circumsolar space. On their way from the sun to the orbit of the earth solar protons will therefore generate fast neutrals by collisions with neutral hydrogen. Depending on the position at its orbit the earth will be hit by these fast neutrals which will come down directly into the thermosphere and will produce temperature and density increases. It is shown that the corpuscular energy flux connected with these fast neutrals will have a semi-annually varying profile along the earth's orbit. Interstellar particle densities of about 5 cm^–3 at infinity would produce energy fluxes of the order of 0.1 erg/cm² sec. Assuming a specific proper motion of interstellar matter surrounding the solar system we obtain a neutral corpuscular energy flux having nearly the same shape and phase as the wellknown semi-annual effect in atmospheric temperatures and densities. Collision-generated, fast neutrals reaching the earth could therefore possibly give an explanation of this effect.Mitteilungen der Astronomischen Institute Bonn, Nr. 102.     

An Improved Red Spectrum of the Methane or T Dwarf SDSS 1624+0029: The Role of the Alkali Metals

The blast-wave model for gamma-ray bursts (GRBs) has been called into question by observations of spectra from GRBs that are harder than can be produced through optically thin synchrotron emission. If GRBs originate from the collapse of massive stars, then circumstellar clouds near burst sources will be illuminated by intense gamma radiation, and the electrons in these clouds will be rapidly scattered to energies as large as several hundred keV. Low-energy photons that subsequently pass through the hot plasma will be scattered to higher energies, hardening the intrinsic spectrum. This effect resolves the "line-of-death" objection to the synchrotron shock model. Illuminated clouds near GRBs will form relativistic plasmas containing large numbers of electron-positron pairs that can be detected within approximately 1-2 days of the explosion before expanding and dissipating. Localized regions of pair annihilation radiation in the Galaxy would reveal past GRB explosions.     

Orbital observations of meteors in the Martian atmosphere using the SPOSH camera

We investigate the expected performance of a wide-angle camera in Martian orbit, which, unlike previous cameras that have flown to Mars, is capable of recording meteor activity in that planet's atmosphere. We show that, based on our current understanding of meteor physics and the interplanetary meteoroid population, several meteors will be detected by this instrument during a single nightside pass on a low Martian orbit. The instrument will also record the signatures of meteor showers expected to occur every Martian year (1.88 Earth years). The results of this investigation will test models of the flux of “large” (mm-cm) meteoroids at the orbit of Mars and their interaction with the Martian atmosphere.     

Effects of rotation on internal structure of the stars

The aim of the present paper will be to establish the explicit form of the equations which govern the internal structure of stars rotating with constant angular velocity formulated in terms of Clairaut coordinates (cf. Kopal, 1980) in which the radial coordinate is replaced by the total potential, which for equilibrium configurations remains constant over distorted level surfaces. The introductory Section 1 contains an account of previous work on rotating stars, commencing with Milne (1923), von Zeipel (1924) and Chandrasekhar (1933), who all employed orthogonal coordinates for their analysis. In Section 2 we shall apply to this end the curvilinear Clairaut coordinates introduced already in our previous work (cf. Kopal, 1980, 1981); and although these are not orthogonal, this disadvantage is more than offset by the fact that, in their terms, the fundamental equation of our problem will assume the form of ordinary differential equations, subject to very simple boundary conditions. The explicit form of these equations — exact to terms of fourth order in surficial distortion caused by centrifugal force—will be obtained in Section 3; while in the concluding Section 4 these will be particularized (for the sake of comparison with work of previous investigators) to stars of initially polytropic structure. These will prove to be much simpler in Clairaut coordinates than they were in any previously used frame of reference. Lastly, in Appendix A we shall present the explicit forms, in Clairaut coordinates, of the differential operators which were needed to establish the results given in Sections 3–4; while Appendix B will summarize other auxiliary algebraic relations of which use was made to formulate our fourth-order theory developed in Section 3.