Invisible Black Hole Detected In Milky Way

MessageToEagle.com – Astronomers using the Nobeyama 45-m Radio Telescope have detected signs of an invisible black hole with a mass of 100 thousand times the mass of the Sun around the center of the Milky Way.

They assume that this possible “intermediate mass” black hole is a key to understanding the birth of the supermassive black holes located in the centers of galaxies.

A team of astronomers led by Tomoharu Oka, a professor at Keio University in Japan, has found an enigmatic gas cloud, called CO-0.40-0.22, only 200 light years away from the center of the Milky Way.

Artist’s impression of the clouds scattered by an intermediate mass black hole. Artist’s impression of the clouds scattered by an intermediate mass black hole. Credits: Keio University.
Artist’s impression of the clouds scattered by an intermediate mass black hole. Credits: Keio University.

The cloud CO-0.40-0.22 is very unusual because of its surprisingly wide velocity dispersion: the cloud contains gas with a very wide range of speeds.

The team found this mysterious feature with two radio telescopes, the Nobeyama 45-m Telescope in Japan and the ASTE Telescope in Chile, both operated by the National Astronomical Observatory of Japan.

The results of the observations show that the cloud has an elliptical shape and consists of two components: a compact but low density component with a very wide velocity dispersion of 100 km/s, and a dense component extending 10 light years with a narrow velocity dispersion.

What makes this velocity dispersion so wide? There are no holes inside of the cloud. Also, X-ray and infrared observations did not find any compact objects. These features indicate that the velocity dispersion is not caused by a local energy input, such as supernova explosions.

Nobeyama Radio Observatory. Credits: Wikipedia
Nobeyama Radio Observatory. Credits: Wikipedia

The team performed a simple simulation of gas clouds flung by a strong gravity source. In the simulation, the gas clouds are first attracted by the source and their speeds increase as they approach it, reaching maximum at the closest point to the object.

After that the clouds continue past the object and their speeds decrease. The team found that a model using a gravity source with 100 thousand times the mass of the Sun inside an area with a radius of 0.3 light years provided the best fit to the observed data.

“Considering the fact that no compact objects are seen in X-ray or infrared observations,” Oka, the lead author of the paper that appeared in the Astrophysical Journal Letters, explains “as far as we know, the best candidate for the compact massive object is a black hole.”

If that is the case, this is the first detection of an intermediate mass black hole.

Astronomers already know about two sizes of black holes:

  • stellar-mass black holes, formed after the gigantic explosions of very massive stars; and
  • supermassive black holes (SMBH) often found at the centers of galaxies.

The mass of SMBH ranges from several million to billions of times the mass of the Sun. A number of SMBHs have been found, but no one knows how the SMBHs are formed. One idea is that they are formed from mergers of many intermediate mass black holes.

But this raises a problem because so far no firm observational evidence for intermediate mass black holes has been found.

Research is published in Astrophysical Journal Letters.

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source: NAOJ