bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Description of the Lunar Orbiter Spacecraft
Authors: Taback Israel 
Published: March 2016

The U.S. Lunar Orbiter Spacecraft Program was conceived to search out potential Apollo landing sites, and to return detailed photographic coverage of the lunar surface for scientific study. The first flight was launched in August 1966, and the successful launch of the fifth orbiter was in August 1967. All five were successful and returned to Earth a large amount of photographic data.Presented in this paper is a short description of the spacecraft system with particular emphasis on the photographic system. The intent is to supply information which will permit a better understanding of the photographic data to be presented by Dr. William Brunk in the following paper.
The Next Decade of Theoretical Solar Physics
Authors: Kuperus M. 
Published: March 2016

Exactly a decade ago an international conference on solar physics took place in Utrecht on the occasion of the late Prof. Minnaert’s 70th birthday. Since then, much has happened. Many new instrumental devices were developed or refined. Completely new observational techniques were applied in the XUV and radio wavelengths and in particle detection.This all resulted in an explosion of new data. Moreover new problems appeared of course. It also resulted in an explosion of papers on solar physics. Actually many more contributions appear than reasonably can be absorbed by the periodical Solar Physics, of which the first volume appeared in 1967. At that time the editors were not at all sure that they would receive enough papers to maintain such a journal. But were there major problems solved recently?At first I would be inclined to think that, notwithstanding the enormous efforts spent in solar physics, little has been achieved and no spectacular breakthroughs have been found. This impression, probably shared by many more colleagues, becomes stronger if one tries to find a line of progress in ‘classical’ problems of solar physics. We still do not have a satisfactory theory of the Sun’s differential rotation and the Sun’s outer convection zone. One may argue that this is due to our bad knowledge of the interior structure which is not accessible to direct observation. Solar activity and the formation of sunspots is now believed to be a direct consequence of differential rotation and cyclonic convective motions and therefore suffers from the same uncertainties.
The Next Decade in Observational Solar Research
Authors: Beckers J. M. 
Published: March 2016

The last two decades have been exceptionally fruitful for astrophysics. Because of very rapid developments, especially in the area of observational astrophysics, our view of the Universe has been substantially completed, challenged and altered. Solar Physics has very much been part of this progress. Developments in space and ground-based technology have virtually completely opened up the entire spectrum of solar electromagnetic and corpuscular radiations. Electromagnetic radiation of the sun can now be studied from gamma ray wavelengths shorter than 10-4 Å to radio wavelengths as long as 1014 Å, a range of approximately 60 octaves. Continuing improvements of spatial resolution of the Sun at all these wavelengths and concommitant development of our theoretical understanding of both the radiative and magneto-hydrodynamic processes on the Sun have made solar physics an exciting field to those interested in the Sun per se, as well as to those who view the Sun as a star whose study aids us in the understanding of astrophysics in a broader sense.A committee of The National Academy of Sciences in the United States under the chairmanship of J. L. Greenstein conducted between 1969 and 1971 a study of the needs of astronomy in the next decade. I took part in this study and it is probably because of this that I was asked to give this review on the next decade in observational solar physics. This review is therefore partly based on the results of the discussions in that committee and in its solar panel. Most of this review will reflect, however, my own opinions.
Interpretation of Carbon Stars Spectra from Model Atmospheres Computations
Authors: Querci F. , Querci M. 
Published: March 2016

The first part of this paper presents a grid of model atmospheres for carbon stars in which the most striking feature is the inclusion of the molecular line blanketing effect of CO, CN and C2 through opacity probability distribution functions. The techniques and the main results have been fully discussed in previous papers (Querci, 1972; Querci et al., 1972 and 1973), and consequently we will give just a rapid description asking the reader to refer to these papers for details. However, the grid has been extended here to lower temperatures.The second part presents original results from the M. Querci’s ‘Thèse d’Etat’ (1974), and concerns the computation of synthetic spectra. A kind of grid of synthetic spectra has been computed from each model atmosphere, that is to say for each particular effective temperature and gravity, over a selected spectral range. The influence of the gravity and of the effective temperature on the computed spectra and the problem of the line cutting procedure are considered. Finally, comparisons with a high resolution infrared spectrum of a carbon star are made.The conclusion summarizes the experimental progress that must be made in order to be able to make meaningful comparisons between predictions and observations.
The Third and Fourth Moments of the Local Stellar Velocity Distribution
Authors: Miller R. H. 
Published: March 2016

AbstractThe velocity moments through the fourth order were calculated for a subset of 870 astrophysically selected stars from Gliese’s catalog. An essential part of this program was the determination of the covariances of estimates of the moments; both sampling and observational error contributions were taken into account in evaluating the total covariance matrix. In applications to the study of galactic structure, the Gliese stars are regarded as tracers of the galactic potential. The moments found are consistent with conventional assumptions about symmetries of the galaxy. Certain galactic parameters, such as the curvature in the law of rotation and the asymmetric drift, were studied with the help of the values obtained for the moments.
How Can It All Be Stable?
Authors: Toomre Alar 
Published: March 2016

My contribution to this Joint Discussion can hardly be termed very novel or original. Rather, I just want to call your attention here to two headaches - one perhaps only a hangover, but the other a real migraine. Sooner or later these two headaches beset anyone who persists in asking how the random motions of stars in the only vicinity where we tolerably observe them can possibly jibe with the sensible presumption that not only our neighborhood but this entire Galaxy should by now be reasonably stable.There is of course nothing strictly ‘local’ about any problem involving the far-reaching gravity. Yet if some conceivable instability of our collection of nearby stars comes even close to deserving such a label, it is surely the Jeans instability or tendency toward gravitational collapse. After all it is not difficult to estimate (e.g., Toomre, 1964) that the most troublesome of such incipient clumpings ought to have significant dimensions (such as half-wavelengths) of the order of 3 or 4 kpc. Even the latter scale is probably not too large a fraction of our distance from the galactic center for ‘local’ analyses in the WKBJ spirit to remain coarsely trustworthy.
Gravitational Collapse and the Formation of the Solar Nebula
Authors: Larson R. B. 
Published: March 2016

AbstractMost theories of the origin of the solar system begin by assuming that, at the time of its formation or shortly afterwards, the Sun somehow acquired a disc-like ‘solar nebula’ in which the planets later formed by accretion. The presently available gravitational collapse calculations, while not yet sufficiently sophisticated to delineate in detail the processes involved, at least support the plausibility of this idea and suggest that the solar nebula may have formed by the accretion or capture of leftover proto-stellar material into orbit around the early Sun. Infall of matter into the disc probably continued for roughly 105 to 106 yr, and may have produced transient strong heating effects through the thermalization of the infall energy in shock fronts. It seems likely that the satellite systems formed in a basically similar way through the capture of residual solid matter into orbit around the planets.A more complete discussion of gravitational collapse and the formation of the solar system has been given in The Origin of the Solar System, ed. H. Reeves, p. 142. (Paris: CNRS).
Supernova Remnants
Authors: Van den Bergh S. 
Published: March 2016

AbstractThe present structure and recent changes in Cas A are discussed. On the deepest available exposures the optical remnant of this supernova is seen to consist of an almost complete shell. The southern part of this shell is outlined by knots that have developed during the last decade. It is pointed out that moving nebulosity in which [O III] radiation is particularly strong is distributed differently from nebulosity in which the [O III]/[S II] ratio is more nearly normal. Observation of the motions of individual knots suggests a model in which dense blobs of matter, which have a highly anomalies composition, become luminous as they plough through a stationary interstellar (or circumstellar) medium.
Astronomy and the Laws of Physics
Authors: Morrison P. 
Published: March 2016

The metaphor of physical law - a range of orderly behavior within certain authoritative constraints - has not escaped the historians of ideas. That scheme, in all its forms, east and west, gained its earliest strength from astronomy itself. The search for measured order in heaven is old and widespread; two instances from ancient China and pre-Columbian Mexico will make the point.For our modern science, two universals rule: that of particulate matter - from neutrons to C2 H5 OH - and the only unsaturable force, long-range gravitation. The phenomena of astronomical scale are mainly examples of kinetic motion resisting for a time that untiring attraction, under the virial theorem. Matter is everywhere familiar, apart from the deep and puzzling question of what seems to be the large-scale failure of matter-antimatter symmetry.
Recent Transient X-Ray Sources
Authors: Willmore A.P. 
Published: March 2016

Prior to the launch of the Ariel V satellite in 1974, four transient X-ray sources had been observed. We placed the study of sources of this type amongst the major objectives of the satellite, and so ensured that the spacecraft ground centre was capable of quick reaction, and that experimenters had rapid access to their data, so that new transients could be rapidly recognised, and an observing programme for them produced and carried out. This has been very successful - in its first 18 months of operation the satellite made observations of at least 14 transients.Of these transients, five form a rather well defined class whose properties are rapidly becoming clearer. This class I shall call the “classical” transient. The remainder form a much more miscellaneous collection which cannot be clearly distinguished from the normal X-ray sources. There is some indication that the classical transients include two species, so to start with I shall describe one of each which has been particularly well-observed by Ariel V and SAS-3.
The Surface of Venus as Revealed by Venera 9 and 10 Probes
Authors: Florensky C.P. 
Published: March 2016

The landers Venera 9 and 10 transmitted to Earth television pictures of the immediate vicinities of landing sites. The pictures were taken by optical-mechanical panoramic cameras looking from view-ports at about 0,9 meter above the ground. The nominal field of view is 40°x l80°. The width of one element of the picture (camera resolution) is 21 minutes of arc. The pictures were subsequently treated by computer enhancement. The first results of panorama analysis were published elsewhere (1,4).Venera 9 landed at the point 32°N, 291°E on the rather steep (˜20°) slope covered by angular sharp-edged rock fragments. The fragments have a horizontal dimension of up to 50 or 70 cm, and a vertical dimension of no more than 15 to 20 cm. Some of the fragments demonstrate the evidence of layering approximately parallel to the flattening of fragments. The surface between fragments is darker than the fragment surfaces of the same orientation and seems to be composed mainly of particles of a size less than the resolution of the camera. The on-board gamma-spectrometer reveals that the radioactivity of the surface at Venera 9 site is similar to radioactivity of basaltic rocks of the Earth ( 2 ).
X-Rays from Clusters of Galaxies
Authors: Culhane J.L. 
Published: March 2016

The discovery of the extended sources of X-ray emission associated with clusters of galaxies was undoubtedly one of the most significant observations carried out by the Uhuru satellite (Gursky et al (1971), Giacconi et al (1974)). At the present time, there are more than 30 identifications and suggested associations of X-ray sources with clusters of galaxies although extended emission has been directly observed in less than 10 cases.The mechanism for X-ray emission from such large objects is of considerable interest. X-rays could be generated by the inverse Compton interactions of microwave background photons with populations of relativistic electrons distributed throughout the clusters. Alternatively the radiation may be due to Bremsstrahlung from hot (T ≃ 108 °K) gas which constitutes an intracluster medium. Progress in understanding the extended X-ray sources and in determining the emission mechanism has come from observations of the X-ray structure and spectra of the cluster sources and it is the purpose of this review to present the current status of these observations.
The Microwave Background Radiation in the Direction of Clusters of Galaxies
Authors: Gull S.F. 
Published: March 2016

The discovery of powerful X-ray sources associated with rich clusters of galaxies has led to the prediction that these clusters contain large amounts of hot gas. A necessary consequence of the existence of such gas is the Compton scattering of cosmic microwave background radiation by hot electrons (Sunyaev & Zeldovich 1972). As a result, some of the microwave photons are re-distributed with slightly higher energies and the effect may be observed as a small diminution in the background temperature. The effect is expected to be ≈0.5 mK for the gas clouds associated with cluster X-ray sources.Previous attempts to detect this effect have not been successful. I present here the results of two further attempts; by Lake & Partridge using the 36’ telescope at Kitt Peak, and by Gull ’ Northover (1976) using the 25-m telescope at the SRC Chilbolton Observatory. Both groups used similar, twin-beam systems, comparing the temperature of the background radiation in the directions of various known X-ray clusters with that at points ≈15 arcmin distant. In order to minimize the effect of non-thermal background sources, it is desirable to observe at the highest frequency compatible with atmospheric stability. Gull & Northover, using a frequency of 10.6 GHz, accumulated 670 hours of observations, whilst Lake & Partridge, who did not have to contend with British weather, selected the more difficult frequency of 33 GHz, but could only manage 80 hours integration.
General Principles for Space Astrometry
Authors: Lacroute P. 
Published: March 2016

In order to obtain very precise positions of the stars on a sphere, it seems absolutely necessary to go out the atmosphere.1 – We avoid atmosphere refraction with always uncertain corrections.2 – We avoid atmospheric turbulence. So the quality of the images is limited by diffraction and not by the seeing.3 – We avoid atmospheric absorption and diffusion limiting the possibilities on the faint stars. Moreover if we observe from an artificial satellite we have no bending of the instruments.In view of very high precision (0″.001) on the directions from an artificial satellite, the difficulty is to obtain sufficient stabilisation in attitude. Also, it is necessary to measure the angles between the stars, instead of the directions relative to the satellite.The mapping of a sphere by angular measurement requires precise measures of large angles; Indeed BACCHUS has shown how that is possible to obtain a precise sphere with relative positions and proper motions, but absolute parallaxes only by precise measures of angles near one value, 90°. Those measures are possible by superposition of two fields in one telescope. A special complex mirror (Fig. I) images the two fields at basic constant angle. We have only to make differential measures to add a small value to the constant.
M Dwarfs at Lower z Distances
Authors: Gliese W. 
Published: March 2016

Twelve years ago, during the International Summer Course at Lagonissi, Bart Bok (1966) presented a paper “Desiderata for Future Galactic Research”. He pointed to the importance of studies in the galactic polar caps which would allow us, as he hoped, to determine some basic data for galactic structure.The significance of his statements was demonstrated already in the following years when the gradual increase of our knowledge of the objects in the solar neighbourhood was suddenly interrupted by new observational data from which diverging conclusions have been drawn. Never before have such controversial opinions on problems in the vicinity of the sun been so eagerly discussed: A formerly unknown numerous population of low-velocity red dwarfs, the mass density resulting from stars three times that formerly thought, a remarkably increased luminosity function - yes or no? Obviously, the controversies have smoothed down again during the last months. But what is the situation after this troubled period? Which problems are still unsolved? Which promising programmes will be proposed? I think this Joint Discussion is justified in 1976!
The Luminosity Function of Late-Type Main-Sequence Stars in the Direction of the North Galactic Cap
Authors: Weistrop Donna 
Published: March 2016

As a result of the recent discussion concerning the luminosity function of late-type main-sequence stars (Weistrop 1976 and references therein), a program of photoelectric photometry of all red stars in a field near the North Galactic Pole was undertaken. The sample is complete for stars redder than (B - V) = 1.40 magnitude for the following apparent magnitude and area limits: V = 12.0-14.0 magnitudes, 13.5 square degrees; V = 14.0-15.0 magnitudes, 3.0 square degrees; V = 15.0-17.5 magnitudes, 1.0 square degree. Observations in BVRI have been obtained for the 44 stars in the sample. Giants and dwarfs are distinguished by their location in the (B - V)-(V - I) diagram or from published proper motion data, where available. The absolute magnitudes of the dwarfs are determined from the MR - (R - I) relation.The density distribution perpendicular to the galactic plane of the dwarfs is consistent with the distribution for K giants found by Oort (1960). The derived luminosity function does not differ significantly from that determined by Wielen (1974) for stars close to the Sun. The local space density for stars in the interval MV = 8.5-14.0 magnitudes is 0.099 stars pc−3. The corresponding stellar density derived from Wielen’s luminosity function is >0.066 stars pc−3. Sixty-six percent of the density derived here is contributed by two stars with absolute magnitude in the range MV = 13.0−14.0 magnitudes.
Some Results of Classification of Stars in Kapteyn Areas Applied to Galactic Structure in NGP
Authors: Kharadze E. K. , Bartaya R. A. 
Published: March 2016

The observational base of our investigation consists of a two-dimensional MK classification of about 11.000 stars in the 42 Kapteyn Areas situated along the gal.lat-s from −17° up to +72° and 200 Ap, Am stars discovered in the same KA. The dispersion of the applied objective-prism spectra is 160 Â per mm. The data are of high accuracy, close to the Michigan level, and uniformity, which make them reliable. The limit is close to the 12-th ph.mg.The general conclusion of the undoubted importance is stated: the galactic concentration of dwarfs is closer than it had been assumed until now; on the other hand - the giants are not so closely concentrated to the galactic plane as it has been accepted.
Progress Report on a Search for Parallax Stars in the Region of the South Galactic Cap
Authors: Murray C. A. 
Published: March 2016

A series of plates is being taken with the U.K. 48-inch Schmidt Telescope at Siding Spring on a field centred on the star GC 1110 near the South Galactic Pole, in order to detect any stars brighter than about mpg = 18, which may have significant trigonometric parallaxes.A search list of more than 16, 300 objects in an area 4¼° × 4¼° has been formed from a preliminary scan on the Galaxy machine at R.G.O. Prom 1974 January to 1976 January some 30 plates have been obtained, nearly half of which have been measured in each of two orientations on Galaxy; each measuring run takes about 16 hours.
Berkeley Studies of Faint Stars at High Latitudes
Authors: Kron Richard G. , Chiu Liang-Tai George , Brooks Kate O. 
Published: March 2016

Several Lick 3-m prime-focus plates of Selected Areas 57, 68, and 51 (taken by I. King) in B, V, and R have been measured for stellar magnitudes down to the plate limit by L. Hinrichs and King, and are currently being measured by Chiu for proper motions (several hundred stars per plate) with the Berkeley PDS microdensitometer. Prime-focus plates are also available from the Hale 5-m and Mayall 4-m telescopes, giving an overall baseline of 20 years. Work so far indicates that on the Lick plates stars brighter then V = 19 can be measured to within one micron standard error; the error becomes unacceptably large for stars fainter than V = 20. A large number of stars bluer than B-V =0.4 show proper motion and are therefore excellent candidates for white dwarfs. For 0.4 ≤ B-V ≤ 0.8, the proper motion stars are expected to be predominantly subdwarfs.The frequency distributions of the stars in V and B-V for the three fields are being analysed by Brooks; the fields are advantageously placed for study of the density distributions in both the disk and the halo. These data should allow the halo stars to be studied out to a distance of 10 to 15 kpc, as well as a determination of the degree of flattening of the halo. Also, a study will be made of the z and ῶ density gradients in the disk, and the luminosity function of disk stars.