BETA-PICTORIS, A YOUNG PLANETARY SYSTEM - A REVIEW

beta Pictoris is a bright southern hemisphere star observed in 1983 by the IRAS satellite as presenting a large and unexpected IR excess. Th is excess was called the Vega-like phenomenon and quickly identified a s due to circumstellar dust. Subsequently in 1984, using stellar coron ography, dust was also directly seen as an edge-on disk extended to se veral hundreds of AUs. Since then, beta Pictoris has been continuously observed. We present here a review of our present understanding of th e beta Pictoris circumstellar environment which still appears unique i n the solar neighborhood. The circumstellar dust disk is predominantly made of relatively large particles (one micron or more) extending out ward to more than 1000 AU and presenting a clearer (dust free) central region away to about 35 AU from the star. The gas is detected through stable and variable spectroscopic signatures revealing a permanent ga s disk with sporadic inflows and also a few outflows. These are partia lly interpreted in terms of evaporation of kilometer-sized bodies very close to the star. Evaporation or destruction through collisions of k ilometer-sized bodies seems to be needed also to explain both the dust as well as the very presence of the CO molecule detected in the circu mstellar gas. Several indirect arguments along with the observation of a very peculiar photometric variation of the star suggests that even giant planets may have already formed in the beta Pictoris system. bet a Pictoris is thus possibly the missing link between young stellar obj ects presenting proto-planetary circumstellar disks and much more evol ved systems in which planets (at least giant ones) are already formed. beta Pictoris is probably a unique place where we may now observe pla netary formation as well as other phenomena that have taken place in t he first 10(8) years of a young stellar system. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.