MPIA Astronomer finds Clues to the
Origin and Evolution of the
least massive Galaxies 
Rochester, NY – Astronomers have uncovered crucial clues to the origin and evolution of an enigmatic class of low-mass galaxies. Dr. Eva K. Grebel, an associate astronomer at the Max Planck Institute for Astronomy in Heidelberg, Germany, is reporting these findings today at the American Astronomical Society meeting in Rochester, NY. Her studies reveal a possible evolutionary link between more massive galaxies and the least massive dwarf galaxies known. These results are of special interest since these dwarf galaxies are considered ancient building blocks of galaxies such as our own Milky Way.
The recently discovered, dim dwarf spheroidal galaxy Peg dSph, which is hiding behind bright foreground stars. Peg dSph is a member of the class of the lowest-mass dwarf galaxies known and a companion of the massive spiral galaxy Andromeda at a distance of 2.5 million lightyears from us. The evolution of Peg dSph was probably affected by the gravitational pull and ram pressure effects from Andromeda, from which it is separated by 880,000 light years.
Picture credit: Grebel and Guhathakurta 1999, obtained with the W.M. Keck II telescope.
Dwarf galaxies are small, dim galaxies that contain many fewer stars than our Milky Way. But what these inconspicuous galaxies lack in size they make up for in numbers: They outnumber more massive galaxies by at least a factor of 10 and are the most numerous galaxies in the Universe. Like chicks around a hen they tend to cluster around high-mass galaxies, but rather than being its offspring they were usually born at the same time. The larger galaxies are thought to have consumed many of their lesser siblings, making today's dwarfs survivors of an earlier much richer dwarf population. Since low-mass dwarf galaxies are usually dominated by populations with ages of several billion years
Max Planck Institute for Astronomy 
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Press Release
Embargoed For Release until 3:40 p.m. EDT, June 5, 2000

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