Sizing up black holes

ST. LOUIS—Astronomers are all wound up over a new method for sizing up supermassive black holes found at the cores of galaxies. The method allows researchers for the first time to estimate the weight of these black holes in spiral galaxies up to 8 billion light-years away, or halfway across the universe, reports Marc Seigar of the University of Arkansas at Little Rock. In a study of 27 spiral galaxies, Seigar’s team found that galaxies such as Andromeda, with the tightest spiral arms, have the biggest black holes, while those with the loosest arms have the smallest. Previously researchers had to measure the velocities of stars in the central region of a galaxy, a method that worked only for relatively nearby galaxies. Details appear in the May 10 Astrophysical Journal Letters.

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