Backward Integrations of motion of the Halley-type comets, covering over 11,000 years, are used to investigate their librations around high-order resonances with Jupiter. These occur for comets moving in direct orbits with revolution periods between 50 and 90 years. The fact that about one halí of them is librating at a time explains the concentration of revolution periods in this range. The librations are of rather uniform period and amplitude, and tend to persist over about 200 revolutions of tho comet. Their presence implies that the lifetimes of these comets since their captures Into periodlc orbits of small perihelion distance mostly exceed 300 revolutions. Possible exceptlons among the 9 comets with present periods of 50 to 90 years are the already extinct P/Westphal, and also P/Halley, for whlch a close approach to the orbit of Jupiter 150 revolutions ago was identified.
We have used force-free extrapolations of photospheric magnetic field observations from Marshall Space Fllght Center to compute the total intensity and circular polarisation of sunspot associated emission from active region 2502 in the period June 13 to 15, 1980. The computed maps were compared to high resolution observations of tne same active region obtained witn tne Westerbork Synthesis Radio Telescope, Tne most interesting aspect of tne active region was tne developement of a new spot between the proceeding and the following spots on June 14, wnich subsequently merged witn the preceeding spot. The new spot
was associated witn enhanced microwave emission with a peak brigtness temperature in excess of 4 10^6 K. Our model computations are In satisfactory agreement witn tne sunspot observations for June 13, nowever tbey falled to reproduce tne
enhanced emission associated witn tne new spot on June 14 and 15. We snow tnat unrealistic values of tne conductive flux are required for the interpretation of tne emission of the new sunspot in terms of thermal processes. We suggest tnat tnis source Is due to gyrosynchrotron radiation from mildly relativistic electrons accelerated by reslstive instabiltles in tne evolvlng magnetic field.
We present near infrared photometric observations in filters J and K of M 32. Isophotal maps with an angular resolution of 93 pc are presented, radial J. K averaged profiles are derived and the
characteristic surface brightness and effective radius are obtained. The isophotal maps show a major axis angular displacement of 25° with respect to the position angle measured by previous authors from B band observations.
8. října 2002 udělila Královská švédská akademie věd Nobelovu cenu za fyziku společně R. Davisovi Jr. a M. Koshibovi za průkopnický příspěvek v astrofyzice, zvláště za detekci kosmických neutrin, a R. Giacconimu též za práce v astrofyzice, které vedly k objevu kosmických rentgenových zdrojů. and Článek doplňují medailonky laureátů: Raymond Davis Jr., Masatoši Košiba, Riccardo Giacconi.