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This report includes some of the major achievements in studies of planets and satellites that have been made during the past three years.
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This is the last triennial report of Commission 42 for this millennium. A great deal has been accomplished in the study of Close Binary Stars (CBS) since the discovery of the first close (eclipsing) binary, Algol, in 1783 by John Goodricke. Now, over 10,000 CBS (most eclipsing variables) are known. More than 5000 of these CBS were discovered over the last several years alone! And many more are expected to be detected over the next few years. Most of these stars were found as spin-offs of microlensing surveys. Interestingly, nearly half of these stars are found outside our Galaxy, primarily in the Magellanic Clouds and M31. Every type of star is represented as a member of a close binary. These include main sequence (as well as pre-main sequence) stars, giants, and supergiants, with the entire possible range of of spectral types and masses represented. Moreover, “dying” stars and “dead” stars, such as white dwarfs, neutron stars, black holes, and, more recently, even brown dwarfs and giant planets (e.g., 51 Peg) have been found as members of close binary systems.
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It has been known that non spherical silicate particles of a size comparable to the wavelength of light, and aggregates of such particles, produce negative polarization in the backscattering region (e.g. Xing & Hanner 1997, Yanamandra-Fisher & Hanner, 1999). It has now been shown that large aggregates of small absorbing particles of fractal dimension about 2 produce a slightly negative polarization at small phase angles (Levasseur-Regourd et al., 1997). The phase-curves strongly differ from those of Mie spheroidal particles. They are likely to be due to scattering by irregular dust particles and/or fluffy aggregates of numerous submicronic absorbing particles (Levasseur-Regourd et al., 1997; Lumme et al., 1997).
Division IV organizes astronomers studying the characterization, interior and atmospheric structure of stars of all masses, ages and chemical compositions.
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The Business Meeting was opened by the president, Imants Platais. He presented the agenda which was unanimously approved. This session was attended by 40 participants. The meeting approved Dafydd Evans as secretary of minutes.
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