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Science 22 August 2003:
Vol. 301. no. 5636, pp. 1055 - 1057
DOI: 10.1126/science.1086836
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Perspectives

ASTRONOMY:
Galactic Encounters

Rosemary Wyse

Studies of the Local Group of galaxies to which the Milky Way belongs are shedding light on some of the processes by which galaxies formed and evolved. In her Perspective, Wyse reviews recent studies of collisions between the Milky Way and smaller satellite galaxies. There is evidence for minor collisions with satellites such as the Sagittarius dwarf galaxy. But the Milky Way does not seem to have suffered any major collisions over the past 10,000 million years, making our galaxy unusual according to galaxy-formation models. Andromeda, another large galaxy in the Local Group, conforms better with expectation, showing evidence for significant recent accretion and/or disruption events.

The author is in the Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA. E-mail: wyse{at}skysrv.pha.jhu.edu

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Science. ISSN 0036-8075 (print), 1095-9203 (online)