Searching for Life in the Solar System ... And Beyond

A Research Discussion Meeting
London, UK - 31 October 1996


Helen Walker, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon

Young stars have large dust disks, but as they mature these are usually lost. In 1983, the Infrared Astronomical Satellite (IRAS) discovered that a normal star (Vega) had a ring of cool dust around it. Other normal stars have been found to show the same type of cool dust. These dust discs may be the sites where planets failed to form, or the remnant, left after planet formation. After the survey of the sky by IRAS, astronomers have waited for the ISO satellite (Infrared Space Observatory) to investigate the dust discus in more detail, since most of the dust discs can be seen only in the infrared. ISO has been used to investigate the size of the dust discs are dominated by silicate dust (small grains of sand), whilst others show the signature of complex organic molecules. The region around Vega has been mapped. This reveals a feature larger than the star alone, showing that ISO can resolve the discs around nearby stars. The dust disc around Vega could be as large as 900 AU across (the Earth is 1 Astronomical Unit from the Sun).