Adaptive optics for large telescopes

The performance of large telescopes is determined both by their angular resolution and by their collection area. It is, therefore, important to achieve as high an angular resolution as possible by site selection, by avoiding image deterioration by the telescope and its environment, and by real time image restoration by adaptive optics. We summarize the principles of adaptive optics, their predicted performance and the current programs underway to implement adaptive optics for astronomical purposes.Paper presented at the Symposium on the JNLT and Related Engineering Developments, Tokyo, November 29–December 2, 1988.     

Book Reviews

Book Revieweds in this article: Victor Moritz Goldschmidt: Father of Modern Geochemistry by Brian Mason Meteorites: The Key to Our Existence by Robert Hutchison and Andrew Graham From Mantle to Meteorites edited by K. Gopalan, Vinod K. Gaur, B. L. K. Somayajulu and J. D. Macdougall Our Universe: An Armchair Guide by Michael Rowan-Robinson. W. H. Freeman Comets: A Chronological History of Observation, Science, Myth, and Folklore by Donald K. Yeomans Dictionary of Minor Planet Names by Lutz D. Schmadel.     

Books and Multimedia Reviews

Book reviewed in this article: Fault-Related Rocks: A Photographic Atlas edited by A. W. Snoke, J. Tullis, and V. R. Todd. The Search for Life on Other Planets by Bruce Jakosky. The Search for Extraterrestrial Life: Essays on Science and Technology edited by Peter Day Cosmic Bullets: High Energy Particles in Astrophysics by Roger Clay and Bruce Dawson. Pluto and Charon edited by S. Alan Stern and David J. Tholen. Fanfare for Earth by Harry McSween, Jr. St.     

Determination and analysis of coronal hole radio spectra

Solar radio maps obtained by our group and others over a wide wavelength range (millimeter to meter) and over a considerable time span (1973–1978) have allowed us to compute the radio spectrum of an average coronal hole, i.e., the brightness temperature inside a coronal hole normalized by the brightness temperature of the quiet Sun outside the coronal hole measured at several different radio wavelengths. This radio spectrum can be used to obtain the changes of the quiet Sun atmosphere inside coronal holes and also as an additional check for coronal hole profiles obtained by other methods. Using a standard solar atmosphere and a computer program which included ray tracing, we have tried to reproduce the observed radio spectrum by computing brightness temperatures at many different wavelengths for a long series of modifications in the electron density, neutral particle density and temperature profiles of the standard solar atmosphere. This analysis indicates that inside an average coronal hole the following changes occur: the upper chromosphere expands by about 20% and its electron density and temperature decrease by about 10%. The transition zone experiences the largest change, expanding by a factor of about 6, its electron density decreases by a similar factor, and its temperature decreases by about 50%. Finally in the corona the electron density decreases by about 20% and the temperature by about 15%.     

Book Review

Natural Glasses by Vladimir Bou?ka, with contributions by Z. Borovec, A Cimbálniková, I. Kraus, A. Lajcáková and M. Pacesová. Academia and Ellis Horwood Origin and Evolution of the Elements edited by N. Prantzos, E. Vangioni-Flam and M. Cassé Annual Review of Earth and Planetary Sciences, Volume 21 , edited by George W. Wetherill, Arden L. Albee and Kevin C. Burke Meteors by Neil Bone     

The light curve analysis of MM Herculis

The photoelectric light curves of MM Her obtained in 1983 and 1984 by Evren (1985, 1987) were analyzed by two different methods. Firsly, the effects of the wave-like distortions on the observations were removed from the observed magnitudes by obtaining its mathematical expression. The remaining light curves were analyzed by using Wood's approach. Later, the light curves of the same years were treated by the method of Wilson-Devinney and distortions seen in the light curves were thought to be explained by locating the spots on the surface of the cooler component. The results obtained by two different approaches are in good agreement.     

Books and Multimedia Review

Book reviewed in this article: Tektite—Zeugen kosmischer Katastrophen by G. Heinen Dana's New Mineralogy—The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Eighth Edition edited by Richard V. Gaines;, H. Catherine W. Skinner, Eugene E. Foord, Brian Mason and Abraham Rosenzweig Tektites, A Cosmic Paradox by Hal Povenmire and edited by John A. O'Keefe 'Silica ‘96’: Meeting on Libyan Desert Glass and Related Desert Events edited by Vincenzo de Michele     

Book and Multimedia Reviews

Book reviewed in this article: Geochronology and Thermochronology by the ⁴⁰Ar/³⁹Ar Method: Second Edition by Ian McDougall and T. Mark Harrison. Protostars and Planets IV edited by V. Mannings, A. P. Boss, and S. S. Russell. The Star Formation Newsletter edited by Bo Reipurth. Astronomical Origins of Life: Steps Towards Panspermia by F. Hoyle and N. C. Wickramasinghe. Here Be Dragons: The Scientific Quest for Extraterrestrial Life by David Koerner and Simon LeVay.     

BOOK REVIEWS

Book reviewed in this article: Meteorite, Urmaterie aus dem interplanetaren Raum by Rolf W. Bühler, Birkhäuser Verlag, Basel, Boston, Berlin, 1988, 192 pp. Kleine Meteoritenkunde by F. Heide. 3rd, totally revised edition by F. Wlotzka Meteorites and the Early Solar System edited by John F. Kerridge and Mildred S. Matthews.     

Book Reviews

Book reviewed in this article: Annual Review of Astronomy and Astrophysics, Volume 32 edited by G. Burbidge, D. Layzer and A. Sandage. Properties and Growth of Diamond edited by G. Davies. INSPEC, the Institution of Electrical Engineers, 1994 Noble Gas Geochemistry and Cosmochemistry edited by J. Matsuda. Explore the Planets by G. Jeffrey Taylor.     

Book and Multimedia Reviews

Book reviewed in this article: The Three Big Bangs: Comet Crashes, Exploding Stars, and the Creation of the Universe by Philip M. Dauber and Richard A. Muller Stars and Their Spectra: An Introduction to the Spectral Sequence by James B. Kaler Impact!: The Threat of Comets and Asteroids by Gerrit L. Verschuur Cosmic Clouds: Birth, Death, and Recycling in the Galaxy by James B. Kaler     

Book and Multimedia Reviews

Book reviewed in this article: Encyclopedia of Planetary Sciences edited by J. H. Shirley and R. W. Fairbridge, Chapman and Hall Asteroids: Their Nature and Utilization by Charles T. Kowal Review of Electronic Imaging in Astronomy: Detectors and Instrumentation by I. S. McLean Galileo's Commandment: An Anthology of Great Science Writing edited by Edmund Blair Bolles. W. H. Freeman The Manson Impact Structure, Iowa: Anatomy of an Impact Crater edited by C. Koeberl and R. R. Anderson     

Book Reviews

Book reviewed in this article: Introduction to Chinese Meteorite Study by Daode Wang et al. An Introduction to the Rock-forming Minerals , 2nd Edition by W. A. Deer, R. A. Howie and J. Zussman. Longman Scientific & Technical with John Wiley & Sons, 1993, 696 pp., $39.95 (ISBN 0–582–30094–0). Atlas of Rock-forming Minerals in Thin Section by W. S. MacKenzie and C. Guilford. Manual of Mineralogy , 21st Edition by C. Klein and C. S. Hurlbut, Jr. To a Rocky Moon: A Geologist's History of Lunar Exploration by Don E. Wilhelms. Scanning Electron Microscopy and X-Ray Microanalysis by Robert Edward Lee.     

The metallic-line star HD 153286

The spectrum of the metallic-line and magnetic star HD 153286 has been studied. The line intensity is constant within the limit of the errors, while the radial velocity is slightly variable. A differential analysis by means of the curve-of-growth method has been made, using 5 And, F5 V as standard star. Moreover, an atmospheric model has been computed; the results of the fine analysis indicate a defect of Sc by a factor of 30 and a defect of Ca by a factor included between 4 and 25; Si, Ti, V, Cr and Fe are normal, Mn, Co, Ni in slight excess by factors included between 2 and 5. Sr, Y, Zr, Ba and La are in excess by factors lower than 10; Ce, Nd and Sm are almost normal; Eu and Gd are in excess by factors of 250 and 4, respectively. These results are compared with the predictions of the diffusion theory.     

Sunspot Observations Made by Hallaschka During the Dalton Minimum

We present and analyse the sunspot observations performed by Franz I.C. Hallaschka in 1814 and 1816. These solar observations were carried out during the so-called Dalton minimum, around the maximum phase of Solar Cycle 6. These records are very valuable because they allow us to complete observational gaps in the collection of sunspot group numbers, improving the coverage for this epoch. We have analysed and compared the observations made by Hallaschka with the records made by other contemporary observers. Unfortunately, the analysis of the sunspot areas and positions showed that they are too inaccurate for scientific use. We conclude, however, that the sunspot counts made by Hallaschka are similar to those made by other astronomers of that time. The observations by Hallaschka confirm a low level of solar activity during the Dalton minimum.     

Books and Multimedia Reviews

Book reviewed in this article: Catalogue of Meteorites, Fifth Edition (Revised and Enlarged) by Monica M. Grady Extrasolar Planets: The Search for New Worlds by Stuart Clark The Moon: Resources, Future Development and Colonization by David Schrunk, Burton Sharpe, Bonnie Cooper and Madhu Thangavelu Rare Earth: Why Complex Life is Uncommon in the Universe by Peter D. Ward and Donald E. Brownlee     

Distribution of iron on Vesta

We have completed a mapping study of 7.6 MeV gamma rays produced by neutron capture by Fe at the surface of the main belt asteroid 4 Vesta as measured by the bismuth germanate scintillator of the Gamma Ray and Neutron Detector (GRaND) on the Dawn spacecraft. The procedures used to determine Fe counting rates are presented, along with a global map, constituting the necessary initial step to quantify Fe abundances. While the final calibration of orbital data to absolute concentrations has not been determined, the range of fully corrected Fe counting rates is compared with that of Fe in howardites. We find that the global distribution of corrected Fe counting rates is generally consistent with mineralogy and composition determined independently by other instruments on the Dawn spacecraft, including measurements of pyroxene absorption bands by the Visible and Infrared Spectrometer and Framing Camera, and an index of diogenitic materials provided by neutron absorption measurements by GRaND. In addition, there is a distinctive low Fe region in the western hemisphere that was not reported by reflectance or optical observations, possibly indicating the presence of a cumulate eucrite component in Vesta's regolith.     

Book Reviews

Book Revieweds in this article: The Shadows of Creation by Michael Riordon and David Schramm. W.H. Freeman From Stone to Star by Claude Allègre GPS Satellite Surveying by Alfred Leick Le Fer de Dieu by Théodore Monod and Brigitte Zanda Meteoritter, nøglen til Jordens Fortid by Vagn F. Buchwald     

Books and Multimedia Reviews

Book reviewed in this article: Fire in the Sky: Comets and Meteors, the Decisive Centuries, in British Art and Science by Roberta J. M. Olson and Jay M. Pasachoff Planetary Materials edited by J. J. Papike Destiny or Chance: Our Solar System and Its Place in the Cosmos by Stuart Ross Taylor Properties of Earth and Planetary Materials at High Pressure and Temperature edited by Murli H. Manghnami and Takehiko Yagi Night Comes to the Cretaceous: Dinosaur Extinction and the Transformation of Modern Geology by James Lawrence Powell