Ursa Major Moving Group

The Ursa Major Moving Group is the closest moving group to Earth, with its core being located roughly 80 light years away. It is rich in bright stars.

Related Topics:
Moving group - Earth - Light year

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It 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.

Related Topics:
1869 - Richard A. Proctor - Dubhe - Alkaid - Big Dipper - Asterism - Proper motion - Sagittarius

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The core of the moving group consists of 14 stars, of which 13 are in the Ursa Major constellation and the other is in the neighboring constellation of Canes Venatici. There is also a "stream" of stars which are scattered more widely across the sky (from Cepheus to Triangulum Australe), which are likely members of the moving group (based on their proper motions and radial velocities and fairly accurate distance data from the Hipparcos satellite).

Related Topics:
Ursa Major - Constellation - Canes Venatici - Cepheus - Triangulum Australe - Radial velocities - Hipparcos

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Some of the brighter stream members include α CrB (Alphecca or Gemma), β Aur, δ Aqr, γ Lep and β Ser; however, Sirius, which was long believed to be a member, may not be, according to research in 2003 by Jeremy King et al. at Clemson University which seems to indicate that it is too young to be a member.

Related Topics:
α CrB - β Aur - δ Aqr - γ Lep - β Ser - Sirius - 2003 - Jeremy King - Clemson University

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The Ursa Major moving group is a real star cluster in space, and would be noticeable from any given direction for a distance of at least several hundred light years. It once was 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, centered some 75 light-years away, making it the closest cluster-like object.

Related Topics:
Open cluster - Nebula - Light-year

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Our Solar System is in the outskirts of this stream, but is not a member, being about 40 times older. Our Sun merely drifted in along its 250 million year galactic orbit, and 40 million years ago was nowhere near these stars.

Related Topics:
Solar System - Sun

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It is believed that the stars in the Ursa Major moving group share a certain chemical signature that may have been characteristic of the nebula from which they were formed: higher than expected levels of barium but lower than expected levels of copper. The abundance of iron seems normal.

Related Topics:
Barium - Copper - Iron

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