Astronomers find a new class of black holes

By studying the star cluster 47 Tucanae scientists have discovered a whole new class of “medium-size” black holes. Until now scientists had identified black holes with less than 100 solar masses, and others with more than 10 000 solar masses (these latter being the monsters found at many galactic cores). The new discovery by scientists from the Harvard-Smithsonian Center for Astrophysics was achieved by studying the motion of stars in aggregate, observing how they moved in relation to one another, and by measuring the scatter of neutron stars, second only to black holes as the densest known objects, across the cluster. Their results suggest a black hole with a mass of around 2 200 solar masses resides at the heart of 47 Tucanae.