Beta Pictoris: A Main-Sequence Disk
Beta Pictoris was found to be an unexpectedly strong source of thermal radiation (from dust) by the IRAS satellite in 1984. Soon after, Smith and Terrile discovered an optical disk around the star. The spectrum of Beta Pic shows red-shifted absorption lines that have been interpreted by some as evidence for comets falling onto the photosphere.
The image above was taken using an optical coronagraph on the University of Hawaii 2.2-m telescope on Mauna Kea. It shows a dust disk extending from North-East to South-West, with a radius of at least 600 AU. The central region of the disk is obscured by a metal spot designed to remove direct light from the central star. The wires holding the spot run North-South and East-West and cause visible artifacts in the image. Scattered background light has been subtracted from the image. Notice that the disk is not completely symmetric. A full account of these asymmetries may be found in the paper cited on the Figure.
The Beta Pic disk is 10 times the size of the known solar system. The optical dust has a lifetime (determined mainly by collisional destruction) that is very short compared to the age of the star (maybe 0.1 Myr compared to 20 Myr). Therefore, the dust is likely to have been recently created. It is possible that collisional pulverisation of embedded, unseen comets (i.e. an unseen Kuiper belt) is responsible. Beta Pictoris provides an example of a so-called debris-disk.
Last updated August 2009 by David Jewitt