Few scientific terms express a sense of sheer enormity more than the word "galaxy." Galaxies are massively massive. They're filled with more stars than any single person could count. They're billions of times brighter than our own Sun! Galaxies are huge! Except for Segue 2.
This dwarf spheroidal galaxy contains only a thousand stars and is just barely visible from Earth because it's so faint. A team of researchers in Hawaii at the W. M. Keck Observatory, the largest observable telescope in the world just published a comprehensive study of Segue 2 in the Astrophysical Journal, revealing that this blip of a galaxy is actually even smaller and dimmer than previously thought. But it's fine because little Segue 2 is cute as can be.
Originally discovered in 2007, Segue 2 is scientifically important for reasons beyond its tininess. At the center of the cosmic entity is a clump of dark matter around which the galaxy spins—scientists consider Segue 2 a galaxy rather than a mere star cluster because of this dark matter. Over a hundred light years away, Segue 2 lies in the Aries constellation on a remote stretch of space, where astronomers always expected to find old, weak star systems. But that's just not the case.
In fact, Segue 2 is incredibly rare. "[Finding Segue 2] has been a major puzzle, suggesting that perhaps our theoretical understanding of structure formation in the universe was flawed in a serious way," says James Bullock, a cosmologist at the University of California, Irvine and author of the new study. "Finding a galaxy as tiny as Segue 2 is like discovering an elephant smaller than a mouse."
(How cute would that be?! An elephant-sized mouse! Too cute, perhaps.)
But seriously, there's a chance that the truly unique nature of Segue 2 could help astronomers better understand the origins of the universe. It could even shed light on the formation of basic elements like carbon and iron. All else fails, it's a pretty special feather for the eggheads at the W. M. Keck Observatory to stick in their hats. Astronomers say that the latest data on Segue 2 couldn't have come from any other observatory in the world.
So tell your friends: To discover undiscoverable galaxies, you must go to Hawaii. And even if you fail, the worst thing that could happen out there is a bit of a sunburn and an overdose of coconut water. The universe works in mysterious ways. [Space.com]
Image by Garrison-Bullock, Kimmel (UCI)