Transactions of the International Astronomical Union Volume XVA : Reports on Astronomy

This volume contains the fifteenth tri-annual reports of the Presidents of the forty Commissions of the International Astronomical Union; it refers to the progress in our discipline during the three years 1970, 1971 and 1972. As compared to earlier volumes a gradual change in character is unmistakable. The ever increasing flow of publications, combined with the obvious necessity to keep the Reports at a reasonable size and price level has gradually forced the Commission Presidents to be more selective than before in drafting their Reports. I have certainly stimulated them into that direction - in order that Reports like these be valuable and lasting, it seems imperative that the individual contributions have the character of a critical overall review, where a fairly complete summary is given of the major develop­ ments and discoveries of the past three years, and in which the broad developments and new trends be clearly outlined, while at the same time essential problems for future research are identified. With respect to the latter item I have suggested the Commission Presidents to add to their reports a brief section on scientific priorities for future research in the field of their Commissions. In order to save space I have suggested to Commission Presidents that references to published papers are given on the basis of their number in the published issues of Astronomy and Astrophysics Abstracts. For instance, the indication (06. 078. 019) or (AAA 06. 078. Front Matter....Pages I-VIII Éphémérides....Pages 1-10 Documentation....Pages 11-14 Astronomical Telegrams....Pages 15-17 Celestial Mechanics....Pages 19-27 Positional Astronomy....Pages 29-41 Instruments and Techniques....Pages 43-73 Solar Activity....Pages 75-128 Radiation and Structure of the Solar Atmosphere....Pages 129-154 Fundamental Spectroscopic Data....Pages 155-177 Phiysical Study of Comets....Pages 179-190 Physical Study of Planets and Satellites....Pages 191-201 The Moon....Pages 203-214 Rotation of the Earth....Pages 215-224 Positions and Motions of Minor Planets, Comets and Satellites....Pages 225-239 Light of the Night-Sky....Pages 241-252 Meteors and Meteorites....Pages 253-273 Photographic Astrometry....Pages 275-283 Stellar Photometry....Pages 285-295 Étoiles Doubles....Pages 297-311 Variable Stars....Pages 313-356 Galaxies....Pages 357-386 Stellar Spectra....Pages 387-405 Vitesses Radiales....Pages 407-414 Time....Pages 415-429 Structure and Dynamics of the Galactic System....Pages 431-466 Interstellar Matter and Planetary Nebulae....Pages 467-506 Stellar Constitution....Pages 507-535 Theory of Stellar Atmospheres....Pages 537-569 Star Clusters and Associations....Pages 571-597 Exchange of Astronomers....Pages 599-600 Radio Astronomy....Pages 601-637 History of Astronomy....Pages 639-646 Photometric Double Stars....Pages 647-667 Astrophysical Plasmas and Magnetohydrodynamics....Pages 669-670 Astronomical Observations from Outside the Terrestrial Atmosphere....Pages 671-695 Spectral Classifications and Multi-Band Colour Indices....Pages 697-716 Teaching of Astronomy....Pages 717-727 Cosmology....Pages 729-735 High Energy Astrophysics....Pages 737-755 Back Matter....Pages 757-760