Scientists Discover Smallest Known Galaxy

Scientists have measured the least massive galaxy ever found, according to a study published in The Astrophysical Journal.

Called Segue 2, the galaxy boasts just 1,000 stars or so, in comparison to the Milky Way’s hundreds of billions, according to NASA.

“Finding a galaxy as tiny as Segue 2 is like discovering an elephant smaller than a mouse,” co-author and UC Irvine cosmologist James Bullock said in a press release.

The discovery, made with the world’s most powerful telescopes at W. M. Keck Observatory, offer tantalizing clues into how iron, carbon and other elements necessary for human life originally formed.

Furthermore, Segue 2’s presence as a satellite of the Milky Way could be “tip-of-the-iceberg observation, with perhaps thousands more very low-mass systems orbiting just beyond our ability to detect them,” Bullock said.

Despite its size, however, researchers are sure that the collection of space bodies is a galaxy and not merely a star cluster as the stars are held together by a globule called a dark matter halo.

First discovered in 2009 as part of the Sloan Digital Sky Survey, the galaxy is one of the faintest scientists know about with a light output of just 900 times that of the Sun. The Milky Way, on the other hand, shines 20 billion times brighter than the Sun.

Still, researchers using different tools at the time thought Segue 2 was much denser.

“The Keck telescopes are the only ones in the world powerful enough to have made this observation,” lead author and postdoctoral scholar Evan Kirby said of the massive apparatus located on the summit of Mauna Kea in Hawaii.

It was through using the telescope that Kirby was able to determine the upper weight range of the 25 major stars in Segue 2, discovering that it weighs at least 10 times less than previously estimated.

Funding for the study was provided by the Southern California for Galaxy Evolution , a multi-campus resaerch program, and by the National Science Foundation.