THE SMALEST GALAXY

Astronomers have spotted the smallest galaxy yet, says Space.com, bolstering a long-held theory about the early makeup of the universe. Known as Segue 2, the tiny galaxy consists of about 1,000 stars held together by a small quantity of dark matter; the nearby Milky Way galaxy, in comparison, has 100 billion stars. “Finding a galaxy as tiny as Segue 2 is like discovering an elephant smaller than a mouse,” says cosmologist James Bullock of the University of California, Irvine.  (click below to read more)

Physicists have long believed that small clumps of dark matter the size of the one in Segue 2 were “almost certainly the first things to form in the universe,” Bullock says. That would mean that thousands of them should still exist, yet until Segue 2 was spotted, astronomers had only ever detected massive collections of dark matter at least a million times the mass of the sun, seeming to point to “some flaw in our theory of how the universe works,” Bullock says. He calls the far smaller Segue 2 “a tip-of-the-iceberg observation,” suggesting that many more such mini-galaxies are out there waiting to be found.