Andromeda strain?

Natural History, July-August, 2004 by Daniel J. Pisano, III

As Charles Liu reported in his "Out There" column ("Gas Guzzlers," 4/04), the discovery of low-mass gas clouds around the Andromeda galaxy is truly groundbreaking work. Because Andromeda is so close to the Milky Way, however, it is exceedingly difficult to determine the distance to the gas clouds. Instead of orbiting Andromeda, they may be on the outskirts of the Milky Way or associated with the stream of gas being pulled from the Magellanic Clouds. Only when analogous gas clouds are found around more distant galaxies will astronomers be certain that such clouds are associated with the formation of galaxies. Such observations are extremely difficult, and may have to await the development of more sophisticated instruments.

Daniel J. Pisano III

Australia Telescope National Facility

Epping, New South Wales, Australia