“The Invisible Galaxy” –100 Million Black Holes Lurking in the Milky Way

 

LIGO Black Holes

 

Astrophysicists have discovered a dozen black holes gathered around Sagittarius A* (Sgr A*), the supermassive black hole in the center of the Milky Way Galaxy, supporting a decades-old prediction, opening up new opportunities to better understand the universe. After conducting a cosmic inventory to calculate and categorize stellar-remnant black holes, astronomers from the University of California concluded that there are probably tens of millions of the enigmatic, dark objects in the Milky Way – far more than expected.

Now, early 2019, a research team led by Shunya Takekawa at the National Astronomical Observatory of Japan noticed HCN-0.009-0.044, a gas cloud moving strangely near the center of the galaxy 25,000 light-years away from Earth in the constellation Sagittarius. They used ALMA (Atacama Large Millimeter/submillimeter Array) to perform high-resolution observations of the cloud and found that it is swirling around a massive invisible object.

Milky Way May Harbor Several Supermassive Black Holes That Roam the Galaxy

Astronomers have detected a stealthy black hole from its effects on an interstellar gas cloud. This intermediate-mass black hole is one of over 100 million quiet black holes expected to be lurking in the galaxy. These results provide a new method to search for other hidden black holes and help us understand the growth and evolution of black holes.

Astronomers think that small black holes merge and gradually grow into large ones, but no one had ever found an intermediate-mass black hole weighing hundreds or thousands of times the mass of the sun.

“Attempt No Voyage Here!” Milky Way Harbors 100 Million Black Holes –‘There are Tens of Millions of these Dark Enigmatic Objects Each the Size of 30 Suns’ (Today’s Most Popular)

Takekawa says, “Detailed kinematic analyses revealed that an enormous mass, 30,000 times that of the sun, was concentrated in a region much smaller than our solar system. This and the lack of any observed object at that location strongly suggests an intermediate-mass black hole. By analyzing other anomalous clouds, we hope to expose other quiet black holes.”

Tomoharu Oka, a professor at Keio University and coleader of the team, adds, “It is significant that this intermediate mass black hole was found only 20 light-years from the supermassive black hole at the galactic center. 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.”

These results were published as Takekawa et al. “Indication of Another Intermediate-mass Black Hole in the Galactic Center” in The Astrophysical Journal Letters on January 20, 2019.

The Daily Galaxy via National Institutes of Natural Sciences

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