Ursa Major Moving Group

The Ursa Major Moving Group, also known as Collinder 285 or Ursa Major association, is a nearby stellar moving group, a set of stars with common velocities in space and thought to have a common origin. Its core is located roughly 80 light years away. It is rich in bright stars including most of the stars of the Big Dipper.

Discovery and constituents

All stars in the Ursa Major Moving Group are moving in roughly the same direction at roughly the same speed, contain roughly the same mix of metal, and, based on stellar theory, appear to be roughly the same age. This evidence suggests to astronomers that the stars in the group share a common origin.

Based on the numbers of its constituent stars, the Ursa Major Moving Group is believed to have once been an open cluster, having formed from a protostellar nebula approximately 500 million years ago. Since then, the sparse group has scattered over a region about 30 by 18 light-years, whose center is currently some 80 light-years away, making it the closest cluster-like object to Earth.

The Ursa Major Moving Group was discovered in 1869 by Richard A. Proctor, who noticed that, except for Dubhe and Alkaid, the stars of the Big Dipper asterism all have proper motions heading towards a common point in Sagittarius. Thus, the Big Dipper, unlike most constellations or asterisms, is largely composed of related stars.

Some of the brighter stream members include Alpha Coronae Borealis (α CrB or Alphecca or Gemma), Beta Aurigae (β Aur),......
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