moving estimate

The Ursa Major Moving Group is the closest moving group to Earth, that is, a set of stars with common velocities in space, 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 in roughly the same location in the Milky Way Galaxy, are moving in roughly the same direction at roughly the same speed, contain roughly the same mix of metals, and, based on stellar theory, appear to be roughly the same age.

Based on the ages 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, which is fairly young. Since that distant time in the past, the sparse group has been scattered over a region about 30 by 18 light-years, whose center is currently some 75 light-years away, making it the closest cluster-like object to the 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 many constellations or asterisms, is actually largely composed of related stars. Resources and References.