THE smallest galaxy known has been found cowering near the outskirts of the Milky Way. Its extremely diminutive size suggests it has been battered to near-extinction by our more massive galaxy. Segue 2 was discovered in 2009 by the Sloan Digital Sky Survey. The faint bundle holds only a few thousand stars, bound by a tiny dark matter halo. The whole caboodle is about 150,000 times the mass of our sun. Evan Kirby at the University of California, Irvine, and his colleagues wanted to check that Segue 2 is a true galaxy that formed on its own rather than being a globular cluster – a tightly bound clump of stars that would have formed in concert with the Milky Way. A galaxy, no matter how small, must be massive enough to hold on to elements heavier than iron, which are released by supernovae. Most such material would be thrown out of a globular cluster. Kirby’s team observed Segue 2 with the Keck telescope in Hawaii and found that it has the chemical composition of a galaxy that has hosted several supernovae and kept hold of the resulting debris (The Astrophysical Journal, doi.org/mtq). If Segue 2 was born this small, it would not have been massive enough to have held on to heavy elements, says Kirby. He thinks it more likely that Segue 2 is the core of a galaxy once 100 times more massive that has been worn to a nub by repeated interactions with the Milky Way. This article appeared in print under the headline “Was tiniest galaxy bullied by a malevolent Milky Way?