spacetoday.net: Ring of stars circles Milky Way

Posted: Tue, Jan 7, 2003, 9:04 AM ET (1404 GMT)
Milky Way halo illustration (RPI)

Astronomers announced Monday that they have discovered a ring of stars of unknown origin circling our galaxy. Using data from the Sloan Digital Sky Survey, astronomers said they located the ring after finding an excess of stars when looking in the direction of the outer edge of the galaxy. The ring, about 120,000 light-years in diameter, contains about one billion stars and is likely held in place by the gravitational effects of dark matter. How the ring formed is uncertain, although astronomers involved in the discovery speculate that it might result from the collision of the Milky Way with a smaller satellite galaxy billions of years ago. One European astronomer told SPACE.com that the ring might also have been created after a disturbance to the main disk of the galaxy kicked out stars. Similar rings have not been found around other galaxies, although the faint surface brightness of the Milky Way's ring might make detections around other galaxies difficult.