(Clearwisdom.net)

The newfound ring as envisioned by the American-led team.	This schematic figure illustrates what the European team's view of the rings geometry, in relation to the spiral structure of the Milky Way.

Two separate groups announced at the 201^st meeting of the American Astronomical Society the discovery of portions of what appears to be a giant ring of previously unseen and surprisingly old stars surrounding our Milky Way Galaxy. If an entire ring exists, theorists might have to rethink details of how the galaxy formed.

Astronomers generally think that most of the galaxy's tens of billions of stars reside within this relatively thin disk and a thicker bulge near the center. Stars are expected to be more numerous toward the center of our galaxy, thinning out towards the edges. The newly discovered ring contains about 100 to 500 million stars. So it was really a surprise to find millions of stars out by the fringe.

The stars in the ring orbit the galactic center at about half the speed of our Sun, said study member Brian Yanny of the Fermi National Accelerator Laboratory. The ring appears to be about 10 times thicker than the disk, Yanny said.

"This ring is unusual in that it appears to consist only of old stars," Rodrigo Ibata of the Observatoire de Strasbourg in France and a member of the European-led team said. "Though there are several galaxies known with bright rings of young stars, none are known to have a ring similar to that of the Milky Way."

Although there are many interpretations about the ring's forming, astronomers believe that this ring is still a puzzle.

Material sources:

http://www.space.com/scienceastronomy/milkyway_ring_030106.html
http://www.cnn.com/2003/TECH/space/01/06/galaxy.ring.reut/index.html