Research suggests Local Cluster is still forming

17 Jun 2002

For decades astronomers have wondered about the origin of certain fast-moving clouds of atomic hydrogen in the vicinity of the Milky Way. In some cases the clouds appeared to be plunging into the plane of the galaxy (at speeds as large as 500 km/sec), and could not be considered as rotating with the galaxy. Later observations showed that some clouds actually seemed to be moving away from the Milky Way.

A synthesis of new radio- telescope measurements plus re-evaluated data from COBE and the Hubble Space Telescope indicates that the clouds may be raw material left over from the formation of the entity known as the Local Group of galaxies, whose largest shareholders are the Andromeda galaxy (with 65% of the mass of the group) and our own Milky Way (30%). Reporting at last week's American Astronomical Society meeting in Toronto, Leo Blitz of UC Berkeley and David Spergel of Princeton said that the high velocity clouds will continue of feed the Milky Way (providing fuel for future star formation) and might even harbor dark matter, a hypothesis which would account for the continued stability of the clouds and their unexplained large internal velocities. Spergel said that the features of his theory for nearby high velocity clouds might apply also to larger, more distant hydrogen clouds in the cosmos.