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Astronomers using Atacama's large millimeter / submillimeter (ALMA) network have spotted waves of molecular gas in orbit around an invisible gravitational source representing 32,000 times the mass of our Sun in the central region of the Milky Way. This intermediate mass black hole is one of the more than 100 million quiet black holes that should be hiding in our galaxy.
The impression of an artist on a cloud of gas swirling around a black hole. Image credit: NAOJ.
Astronomers know that black holes about 10 times to 100 times the mass of the Sun are the remains of dying stars and that supermassive black holes, more than 100,000 times the mass of the Sun, inhabit the centers of most galaxies .
But scattered throughout the Universe, there are some apparent black holes of a more mysterious type.
With solar masses ranging from 100 to 100,000, these intermediate-mass black holes are so difficult to measure that even their existence is sometimes disputed.
Dr. Shunya Takekawa of the National Astronomical Observatory of Japan and her co-authors used ALMA to make high-resolution observations of HCN-0.009-0.044, a gas cloud moving strangely near the center of the Milky Way .
They concluded that HCN-0.009-0.044 was swirling around an invisible massive object.
"Detailed kinematic analyzes have revealed that a huge mass – 32,000 times that of the Sun – was concentrated in a region much smaller than our solar system," said Dr. Takekawa.
"This and the lack of object observed at this location strongly suggests a black hole of intermediate mass."
"By analyzing other abnormal clouds, we hope to expose other calm black holes."
HCN-0.009-0.044 is located at a projected distance of only 23 light-years from Sagittarius A *, the supermassive black hole located in the center of our galaxy.
"It is significant that this mid-mass black hole was discovered just 23 light-years away from the supermassive black hole of the galactic center," said co-author Professor Tomoharu Oka, astronomer at Keio University.
"In the future, he will fall into the supermassive black hole; a bit like gas is falling into it right now. "
"This supports the black hole growth merging model."
The study appears in the Letters from the Astrophysical Journal.
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Shunya Takekawa et al. 2019. Indication of another black hole of intermediate mass in the galactic center. ApJL 871, L1; doi: 10.3847 / 2041-8213 / aafb07
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