Science and Medicine : Star Catalogue on CDs

Astronomers have completed the most comprehensive star catalogue and map ever, so large that if printed, it would fill 400 volumes and weigh one ton. So they put it on compact discs instead--the location and brightness of 18,819,291 celestial objects--and last month mailed sets to observatories around the world.

The Guide Star Catalog took astronomers and computer programmers at the Space Telescope Science Institute in Baltimore eight years to amass. The new inventory is more thorough than the previous one, which mapped a paltry 250,000 celestial objects, compared to the almost 19 million listed now.

The catalogue will be used by astronomers at ground-based observatories, as well as those operating NASA’s Hubble Space Telescope, the orbiting observatory that is scheduled for launch next March. The database is a crucial component for the Hubble telescope. It will allow astronomers to point the telescope with greater accuracy and keep it locked on objects by using nearby stars as landmarks, or skymarks, said project manager Michael Shara. The next guide to the universe will attempt to inventory 2 billion objects, he said.