Segue 2 is record-setting tiny galaxy held together by dark matter

Jun 11, 2013

Sometimes big things come in small packages, or so the saying goes. Such is the case with Segue 2, the name of a tiny galaxy near our own that is being called the "most lightweight" ever discovered. What's more, however, is the reality that its relatively small number of stars are bound together with dark matter, distinguishing it from a star cluster.

Segue 2 is notable because it is such a small galaxy, holding only about 1,000 stars that orbit the Milky Way. The tiny galaxy was first discovered back in 2009, but at that point researchers didn't know whether it was a cluster of stars or a legitimate galaxy. University of California at Irvine scientists set out to determine which was the case this year.

In doing so, the researchers used the W. M. Keck Observatory, which is located in Hawaii and contains a pair of telescopes measuring in at about 30-feet each. Segue 2 was measured, and its 25 seemingly "most prominent" planets were determined. Each of those 25 planets then had their weights estimated based on calculations, and those resulting weights were used to determine that the tiny galaxy is is even lesser in stature than originally thought - by a factor of about 10, according to Science Recorder.

Such a tiny galaxy is known as a dwarf galaxy, and it has been a widely-held belief that the Milky Way is orbited by many such galaxies. The problem has been finding them, however. Because of their small size, they are typically dark compared to larger galaxies, and without adequate lighting, we're unable to see them.

As technology increases and telescopes become more powerful and sensitive, the number of discoveries of galaxies that were previously too dim could rise, providing scientists with more data to help figure out the universe's mysteries. For now, however, the researchers have Segue 2, which is being used to study the formation of galaxies.

SOURCE: Science Recorder

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