Intrigued by a swirling cloud of gas near the heart of the Milky Way, a team of astronomers led by Shunya Takekawa at the National Astronomical Observatory of Japan used the Atacama Large Millimetre/submillimetre Array to measure its motion and concluded the only explanation was a previously unknown intermediate-mass black hole.
The “quiet” black hole is located just 20 light years from the supermassive four-million-solar-mass black hole lurking at the centre of the Milky Way.
“Detailed kinematic analyses (of the newly-discovered hole) revealed that an enormous mass, 30,000 times that of the Sun, was concentrated in a region much smaller than our Solar System,” Takekawa said. “This and the lack of any observed object at that location strongly suggests an intermediate-mass black hole. By analysing other anomalous clouds, we hope to expose other quiet black holes.”
Black holes are the collapsed remnants of massive stars with gravity so extreme not even light can escape. But they can be detected by gravitational interactions with their immediate environment and though the emission of high-energy radiation as gas and dust are sucked in and heated to enormous temperatures.
They range in mass from about five to millions of times the mass of the Sun. Astronomers believe small black holes can merge and slowly grow into the supermassive holes found at the cores of many, if not all, mature galaxies.
“It is significant that this intermediate mass black hole was found only 20 light-years from the supermassive black hole at the galactic centre,” said Tomoharu Oka, a professor at Keio University and co-leader of the team. “In the future, it will fall into the supermassive black hole, much like gas is currently falling into it. This supports the merger model of black hole growth.”