Ursa Major Moving Group
From Biocrawler, the free encyclopedia.
In 1869, Richard A. Proctor noticed that, except for Dubhe and Alkaid, the stars of the Big Dipper all have proper motions heading towards a common point in Sagittarius. A few other members have been identified, notably Alphecca in Corona Borealis, and it has been given the name Ursa Major Moving Group.
This group of stars once was an open cluster. Since that distant time in the past, the sparse group has been scattered over a region about 30 by 18 light-years, centered some 75 light-years away, making it the closest cluster-like object.
About 100 other stars, including Sirius, form a stream sharing approximately the same proper motion as the ex-cluster, but the exact relationship is unclear. Our Solar System is in the outskirts of this stream, but is not a member, being about 40 times older.
