Second Largest Black Hole In Milky Way May Have Been Discovered

Posted: Jan 15 2016, 11:37pm CST | by , Updated: Jan 16 2016, 1:37am CST, in News | Latest Science News


Second Largest Black Hole in Milky Way May Be Discovered
Artist’s impression of the clouds scattered by an intermediate mass black hole. Credit: Tomoharu Oka/Keio University

The possible intermediate black hole holds the key to understand the evolution of supermassive black holes

A team of Japanese astronomers have detected the signs of second largest black hole in our galaxy Milky Way.

Using the Nobeyama 45-meter radio telescope, researchers have found an enigmatic cloud of gas just 200 light years away from the center of the galaxy Milky Way. And it hints on the presence of a possible ‘intermediate mass’ black hole with a mass 100 thousand times the mass of the Sun. 

The gas cloud, called CO-0.40-0.22, is not an ordinary gas cloud, it contains gas with a very wide range of speeds.

For having a close look at the structure, researchers from National Astronomical Observatory used two radio telescopes, Nobeyama 45-m telescope in Japan and the ASTE telescope in Chile. Researchers have found that the cloud has an elliptical shape and it contains two components. One compact component has low density but very wide velocity dispersion of 100 kilometer per second while other is dense stretching 10 light years with narrow velocity dispersion. Velocity dispersion explains the range of speeds at which matter is moving.

Researchers were perplexed about what was causing velocity dispersion so wide despite the fact there are no holes or compact object in the structure. It is an indication that velocity dispersion is not triggered by a local energy input like supernova explosion.

Therefor, researchers designed a computer model to stimulate the enigmatic gas clouds where clouds were seen going through a strong gravity source. In the simulation, the gas clouds were first attracted by the gravity source. Their speeds increased as they approached it and reached their maximum potential as they came closest to the object. As the clouds continue past the object, their speed decreased.

Researchers believe this result is the first evidence of an intermediate mass black hole presence.

"Considering the fact that no compact objects are seen in X-ray or infrared observations…as far as we know, the best candidate for the compact massive object is a black hole." Tomoharu Oka, a professor at Keio University and lead author of the study said.

There are two categories of black holes have been discovered so far: stellar-mass black holes which were formed after the gigantic explosions of very massive stars and supermassive black holes often found at the centers of galaxies. But scientists are not sure how the later ones are formed. One idea is that they are formed from mergers of many intermediate mass black holes but no firm observational evidence for intermediate mass black holes has been found yet. If the cloud CO-0.40-0.22, lurking in Milky Way, contains an intermediate black hole, it will support the black hole merger theory. If that is the case, this intermediate black hole holds the key to understand the birth of supermassive black holes located in the centers of galaxies.

A separate study suggests that there are100 million black holes in our galaxy Milky Way but only few dozen are found so far while recent observations through radio telescopes reveal that there are a number of wide-velocity-dispersion compact clouds similar to CO-0.40-0.22. 

"Investigations of gas motion with radio telescopes may provide a complementary way to search for dark black holes" said Oka. "The on-going wide area survey observations of the Milky Way with the Nobeyama 45-m Telescope and high-resolution observations of nearby galaxies using the Atacama Large Millimeter/submillimeter Array (ALMA) have the potential to increase the number of black hole candidates dramatically."

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Hira Bashir covers daily affairs around the world.




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