Thousands of superdense neutron stars and midget black holes lurk near the center of our galaxy, according to new X-ray studies of the sky. The stellar-mass black holes are each just 10 times the mass of the sun, much smaller than the supermassive black hole known to inhabit the Milky Way's center. That central black hole has an estimated mass of 3.7 million suns. Each neutron star is about the mass of the sun.
Using the orbiting Chandra X-ray Observatory, Michael P. Muno of the University of California, Los Angeles (UCLA) and his colleagues found four dramatically flickering X-ray sources within 3 light-years of the Milky Way's supermassive black hole, known as Sagittarius A. The large fluctuations in these objects' brightness suggest that they are black holes and neutron stars stealing matter from companion stars. Stellar-mass black holes and neutron stars both form from the collapsed cores of stars that died in supernova explosions.