BENEFACTORS can be too generous. Exploding stars in a small galaxy called Leo P pumped out heavy elements with such vigour that most of them sailed off into space.
鈥淚t鈥檚 tough being a little galaxy,鈥� says at the University of Texas at Austin. Not only does a dwarf galaxy鈥檚 feeble gravity fail to retain debris from supernovae that explode within it, but giant galaxies such as the Milky Way can also raid the dwarf of stars and gas.
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Dozens of dwarf galaxies orbit the Milky Way, and all have low levels of heavy elements. But we didn鈥檛 know how much of the dwarfs鈥� poverty to attribute to our galaxy鈥檚 thieving ways, or how much material simply escaped.
Enter Leo P, a small galaxy 5.3 million light years from Earth that astronomers . 鈥淚t鈥檚 the perfect laboratory,鈥� McQuinn says: it lies just beyond the Local Group, the gathering of nearby galaxies that includes our own, so no other galaxy interferes with its development.
McQuinn and her colleagues decided to look at oxygen, the most abundant element heavier than hydrogen and helium. Using models of how much oxygen Leo P鈥檚 massive stars should have produced and subsequently cast out when they exploded, the team found that the galaxy has lost 95 per cent of its oxygen, even without the Milky Way鈥檚 meddling ().
Still, similar galaxies orbiting the Milky Way have lost 98 to 99 per cent of their heavy elements. 鈥淟eo P has been wise to keep its distance from us,鈥� McQuinn says.
(Image: Hubble Space Telescope; NASA, ESA, and Kristen McQuinn (University of Texas at Austin))
This article appeared in print under the headline 鈥淪mall galaxies lose gas to self-sabotage鈥�
