Protoplanetary Disks Seeen in Projection
Above are Hubble Space Telescope images by Mark McCaughrean and Bob O'Dell, taken
towards the Orion star formation region. Seen in silhouette against the background
luminous gas are several elliptical objects with length scales of 100's to 1000's of
AU. They are most likely protoplanetary disks. The central bright spot (easily seen
in the lower right panel) is light from the protostar leaking out through the disk.
The opacity in the disks is due to dust. It is nice to think that the dust in these
systems is sticking to grow into pebbles and planetesimals. We know from observations
of other young stars that this process of accumulation happens within a few million
years of the formation of the disk. Eventually, the dust will be trapped inside
macroscopic bodies like comets and planets.
Last updated December 1997 by David Jewitt
