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NASA scientists have identified the lightest black hole yet, just 3.8 times the mass of the sun, in a binary star system in the Milky Way known as XTE J1650-500. The next smallest black hole, spotted in 1994, weighed in at 6.3 solar masses. Either of those specimens would pale next to the supermassive black holes that are presumed to lurk at the centers of galaxies such as our own—each as heavy as billions of suns. Discovering the lower size limit of black holes, however, is key to identifying the dividing line that separates them from neutron stars, which is important for fundamental physics because it tells scientists how matter behaves at extraordinarily high density. Astronomers found their new lightweight champ (shown here in an artist's conception) by searching for so-called quasiperiodic oscillations in starlight using NASA's Rossi X-Ray Timing Explorer satellite. They estimate its diameter at 15 miles, but don't let its size fool you: Researchers note that teensy black holes like this one have stronger tidal forces than their larger kin, and could stretch your body into a strand of astro-spaghetti. Now that's one spicy meatball.
