Ursa Major Moving Group - Discovery and Constituents

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 metals, 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 (Eta Ursae Majoris), 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), Delta Aquarii (δ Aqr), Gamma Leporis (γ Lep) and Beta Serpentis (β Ser). More bright and moderately bright stars which are currently believed to be members of the group are listed in two sections below: Core stars and Stream stars.

Read more about this topic:  Ursa Major Moving Group

Famous quotes containing the words discovery and/or constituents:

    That the discovery of this great truth, which lies so near and obvious to the mind, should be attained to by the reason of so very few, is a sad instance of the stupidity and inattention of men, who, though they are surrounded with such clear manifestations of the Deity, are yet so little affected by them, that they seem as it were blinded with excess of light.
    George Berkeley (1685–1753)

    Will mankind never learn that policy is not morality,—that it never secures any moral right, but considers merely what is expedient? chooses the available candidate,—who is invariably the devil,—and what right have his constituents to be surprised, because the devil does not behave like an angel of light? What is wanted is men, not of policy, but of probity,—who recognize a higher law than the Constitution, or the decision of the majority.
    Henry David Thoreau (1817–1862)