Highlights of Astronomy

Ken Freeman I would like to pick out a few items that I found particularly interesting. The choice probably reflects my ignorance, because many of these topics are no doubt more known to most of you. I am fairly sure that some of them are basic and important. We will start with the first session. There were three closely related papers on the evolution of massive stars, the formation of open clusters and associations and the IMF. We learned that clusters appear to form in initially bound clouds 6 of masses between 10'+_10 M , but star formation is a destructive process. Most of the gas is@ lost and the remaining stars then find themselves in an unbound system, which naturally disperses on a dynamical time. As a result of this, star formation is typically a fairly inefficient process, at least on the scale of open clusters. However (as Heggie pointed out) it seems to be somewhat more efficient on smaller scales, as evidenced by the fairly high incidence of binary stars. To form a bound cluster requires a higher efficiency of star formation, typically 30% or more, and we see how the three papers of this morning session relate: the initial mass function and the timing of where and when the DB stars form dictate the likely fate of the system.

Inhalt
Invited Discourses.- Pulsars and their Genesis.- Dark Matter in the Universe.- Venus.- Joint Discussions.- 1. Reference Frames.- Uses and Required Characteristics of Reference Frames for Galactic Astronomy.- Reference Frames for Minor Planets, Comets and Satellites.- Reference Frames and the Extragalactic Distance Scale.- Requirements for Earth Rotation Parameters.- Ephemerides and Celestial Mechanics.- Status Report on the Work on the FK5.- J2000.0.- Classical Absolute/Differential Programs.- The Background to the MERIT/COTES Recommendations on the Terrestrial and Celestial Reference Systems.- HIPPARCOS and Celestial Reference Frame.- The Use of the Hubble Space Telescope for Global Reference Frame Work.- Proper Motions Referred to Faint Galaxies.- Reference Frame Studies at JPL/ Caltech.- On the Use of Natural References.- Relativistic Reference Frames in Astrometry.- Comparison of the Optical and Radio Reference Frames.- The Promise of Optical/IR Interferometry and Space Astrometry.- Reference Frame/Coordinate System in General Relativity.- Discussions.- 2. Long-Period Eclipsing Binary Stars and Related Objects.- Photometry of the Recent Eclipse of Epsilon Aurigae.- A Spectroscopic View of Epsilon Aurigae.- Interpretation of the Data of Epsilon Aurigae.- Observation and Interpretation of Zeta Aurigae Stars.- Related Binaries, Including Symbiotic Stars.- Mass Transfer and Evolution in Long-Period Binary Systems.- Wind Accretion and Interaction in Long Period Binary Systems.- Summary and Critique of Joint Discussion II.- Extraction of the Shell Spectrum of Epsilon Aurigae.- Dynamics of the Epsilon Aurigae Ring Model.- Interim Discussion of the Orbit of ? Sagittae.- Evidence for the Roche Lobe Overflow in VV Cephei.- Infrared Michelson Interferometry of Zeta AurigaeType Supergiants.- Very Long Period Supergiant Semidetached and Contact Systems.- 3. Solar and Stellar Nonradial Oscillations.- Progress and Problems in the Study of the Pulsating White Dwarf Stars.- The PG1159 Variables.- Non-Radial Oscillations in ? Scuti Stars and Rapidly Oscillating Ap Stars.- Beta Cephei Variables.- Nonradial and Radial Oscillations Observed in Non-Emission Line OB Dwarfs and Giants.- Non-Radial Pulsation in Be Stars.- Radial and Non-Radial Pulsations in Wolf-Rayet Stars and in Supergiants.- Solar and Solar-Like Oscillations: Theory.- 4. Radio Astronomy and Cosmology.- Cosmic Microwave Background Spectrum Measurements.- The Angular Distribution of the Cosmic Background Radiation.- Ovro Results on the Sunyaev-Zel'dovich Effect, 19831985.- The Microwave Background from Cambridge.- Searches for Primordial Pancakes.- Intergalactic Neutral Hydrogen.- The Nature of Faint Radio Sources.- Is the Upturn in the Source Counts Caused by Primeval Radio Galaxies ?.- A New Deep VLA Radio Survey at 6 cm.- Dependence of Linear Sizes and Spectral Indices of Extended Radio Galaxies on Redshift and Radio Luminosity.- Abundances of the Very Light Elements (D, 3He, 4He and 7Li) and Primordial Nucleosynthesis.- 5. Stellar Activity: Rotation and Magnetic Fields.- Stellar Dynamo Characteristics.- Stellar Activity Cycles.- On the Rotation-Activity Connection.- Convection as a Regulator of Dynamos.- The Measurement of Stellar Photospheric Magnetic Fields.- The Dichotomy Between CO Absorptions and Ca II Emissions in the Sun and Stars: An Indirect Diagnostic for Gas Disturbed by Magnetic Fields ?.- Starspots and Plages.- A Study of Three RS CVn-type Eclipsing Binaries.- Coronal Magnetic Fields.- Properties of Stellar Magnetic Fields in Close Binaries Deduced fromNon-thermal Radio Observations.- Stellar X-ray and Radio Activities and Coronal Magnetic Field.- On Active Stars, Coronal Loops, Magnetic Braking and All That.- 6. Evolution in Young Populations in Galaxies.- The Concept of Young Populations.- Evolution of High Mass Stars.- The Dynamical Evolution of Young Clussters and Associations.- The Initial Mass Function in Young Star Clusters.- Discussion.- Structure and Evolution of Giant Molecular Clouds.- Molecular Clouds in M51 and in the Galaxy.- The Molecular Cloud Content of Spiral and Dwarf Galaxies.- Discussion.- Star Formation, Giant HII Regions and Spiral Structure.- Young Stars and Star Formation in Normal Irregular Galaxies.- Discussion.- Chemical Evolution of Galaxies.- Star Formation Bursts in Galaxies.- Discussion.- Summary.- 7. Supernovae.- Centenary of S Andromedae (SN 1885a).- Problems of Observing Nearby Galaxies Visually.- Some Possible Identification Between Chinese Guest Stars and Supernova Remnants.- Supernovae in Flocculent and Grand Design Galaxies.- Recent Optical Observations of Supernovae.- Supernovae and Stellar Mass Loss.- Models for the Early and Late Spectra of Supernovae.- NL TE-Effects in Supernovae Type II Photospheres.- Models of Type II Supernova Explosions.- Effects of Angular Momentum on Supernova Explosion and Stability of Rapidly Rotating Stellar Cores.- Gravitational Radiation by a Collapsing Rotating Stellar Core.- Phase Transitions of Superdense Matter and Supernova Explosion.- X-ray Emission from Supernova Remnants.- Supernovae and Cosmology.- VL BI Observations of the Compact Components in M82.- Radio Supernova Candidates in the M82 Starburst.- Joint Commission Meetings.- Hipparcos.- The ESA Space Astrometry Mission: Overview and Status.- Activities of the Input Catalogue Consortium.- Preparation of the Mission: Earth-based Photometry.- Preparation of the Mission: Earth-based Astrometry.- Activities of the Data Reduction Consortia.- Tycho: Photometry & Astrometry for more than 500 000 Stars.- The Tycho Input Catalogue.- Link with Extragalactic Reference Frames.- Coronal Activity and Interplanetary Disturbances.- Coronal Activity at Radio Wavelengths.- Coronal Response to Energy Release During Solar Flares.- Correlated Observations of Impulsive UV and Hard X-ray Bursts from the Solar Maximum Mission.- Coronal Mass Ejections.- The Sources of Major Heliospheric Disturbances.- The Response of Microwave Emission to the Development of Active Regions.- Coronal Holes and Flare Related Phenomena.- Coronal Structures Observed at Meter Wavelengths.- The Nançay Multifrequency Radioheliograph.- An Energy Storage Mechanism for a Solar Flare by Shearing the Magnetic Field.- Merit + Cotes.- Joint Summary Report of the IAU/IUGG Working Groups on the Rotation of the Earth and the Terrestrial Reference System.- Report of Joint Meeting Held on 1985 November 22 to consider the MERIT/COTES Recommendations for a New International Earth-rotation Service.- Synthetic Photometry.- Principles and Scope of Synthetic Photometry.- The Possibilities of Synthetic Photometry.- Passbands and Photometric Systems.- Observed …