1 STRUCTURE AND EVOLUTION OF NEARBY OB ASSOCIATIONS
We present the rst results of a comprehensive census of the stellar content of the nearby OB associations based on Hipparcos positions, proper motions and parallaxes for 12842 candidate member stars distributed over 21 elds on the sky. We use a new method to identify moving groups in these elds (see de Bruijne et al., these proceedings). Previously, astrometric membership in nearly all the nearby OB associations was known only for stars with spectral types earlier than B5. The Hipparcos measurements now allow us to identify members down to late F. This census provides a rm basis for studies of galactic and extragalactic star forming regions.
The Gum nebula and related problems
Papers were presented in conference sessions on the Gum nebula, the Vela X remnant, the hot stars gamma Velorum and zeta Puppis, the B associations in the Vela-Puppis complex, and pulsars. Ground-based optical and radio astronomy; rocket and satellite observations in the radio, visible, ultraviolet, and X-ray regions; and theoretical problems in the physical state of the interstellar medium, stellar evolution, and runaway star dynamics were considered.
Survey of Galactic Radio-Noise at 200 Mc/s
A survey of galactic radio-noise at 200 Mc/s, has been made for the region of the sky south of declination 45 °N. Results are expressed graphically in watts m.-2 (c/s.)-1 (steradian)-1, the maximum value being 20 x 10-21 W. m.-2 (c/s.)-1 (steradian)-1 at galactic latitude -3° and longitude 322°. Corrections have been made for the aerial beam width. No measurement has been made of the residual intensity from the coldest parts of the sky (the galactic poles) and this quantity, when known, should be added to the results quoted. The galactic noise provides a permanent and convenient standard for solar noise measurements, and its intensity for this purpose is evaluated.