Another Monster Black Hole Found in the Milky Way

At the center of the Milky Way Galaxy resides the

Supermassive Black Hole

(SMBH) known as

Sagittarius A*

. This tremendous black hole measures an estimated 44 million km in diameter, and has the mass of over 4 million Suns. For decades, astronomers have understood that most larger galaxies have an SMBH at their core, and that these range from hundreds of thousands to billions of Solar Masses.

However, new research performed by a team of researchers from Keio University, Japan, has made a startling find. According to

their study

, the team found evidence of a mid-sized black hole in a gas cluster near the center of the Milky Way Galaxy. This unexpected find could offer clues as to how SMBHs form, which is something that astronomers have been puzzling over for some time.

The study, titled "

Millimetre-wave Emission from an Intermediate-mass Black Hole Candidate in the Milky Way

", recently appeared in the journal

Nature Astronomy.

Led by Tomoharu Oka, a researcher from the Department of Physics and the

School of Fundamental Science and Technology

at Keio University, the team studied CO–0.40–0.22, a high-velocity compact gas cloud near the center of our galaxy.

[caption id="attachment_65647" align="aligncenter" width="580"]

This artist's concept shows a galaxy with a supermassive black hole at its core. The black hole is shooting out jets of radio waves.Image credit: NASA/JPL-Caltech

[/caption]

This compact dust cloud, which has been a source of fascination to astronomers for years, measures over 1000 AU in diameter and is located about 200 light-years from the center of our galaxy. The reason for this interest has to do with the fact that gases in this cloud - which include hydrogen cyanide and carbon monoxide – move at vastly different speeds, which is something unusual for a cloud of interstellar gases.

In the hopes of better understanding this strange behavior, the team originally observed CO–0.40–0.22 using the 45-meter radio telescope at the

Nobeyama Radio Observatory

in Japan. This began in

January of 2016

, when the team noticed that the cloud had an elliptical shape that consisted of two components. These included a compact but low density component with varying velocities, and a dense component (10 light years long) with little variation.

After conducting their initial observations, the team then followed up with observations from the

Atacama Large Millimeter/submillimeter Array

(ALMA) in Chile. These confirmed the structure of the cloud and the variations in speed that seemed to accord with density. In addition, they observed the presence of radio waves (similar to those generated by Sagittarius A*) next to the dense region. As they state in their study:

[caption id="attachment_134655" align="aligncenter" width="525"]

Change image showing the area around Sgr A, where low, medium, and high-energy X-rays are red, green, and blue, respectively. The inset box shows X-ray flares from the region close to Sgr A. NASA: NASA/SAO/CXC

[/caption]

The team also ran a series of computer models to account for these strange behaviors, which indicated that the most likely cause was a black hole. Given its mass - 100,000 Solar Masses, or roughly 500 times smaller than that of Sagittarius A* - this meant that the black hole was intermediate in size. If confirmed, this discovery will constitute the second-largest black hole to be discovered within the Milky Way.

This represents something of a first for astronomers, since the vast majority of black holes discovered to date have been either small or massive. Studies that have sought to locate Intermediate Black Holes (IMBHs), on the other hand, have found very little evidence of them. Moreover, these findings could account for how SMBHs form at the center of larger galaxies.

In the past, astronomers have conjectured that SMBHs are formed by the merger of smaller black holes, which implied the existence of intermediate ones. As such, the discovery of an IMBH would constitute the first piece of evidence for this hypothesis. As Brooke Simmons, a professor at the University of California in San Diego, explained in an interview with

The Guardian:

[caption id="attachment_136135" align="aligncenter" width="580"]

Artist's impression of two merging black holes, which has been theorized to be a source of gravitational waves. Credit: Bohn, Throwe, Hébert, Henriksson, Bunandar, Taylor, Scheel/SXS

[/caption]

Further studies will be needed to confirm the presence of an IMBH at the center of CO–0.40–0.22. Assuming they succeed, we can expect that astrophyiscists will be monitoring it for some time to determine how it formed, and what it's ultimate fate will be. For instance, it is possible that it is slowly drifting towards Sagittarius A* and will eventually merge with it, thus creating an even more massive SMBH at the center of our galaxy!

Assuming human beings are around to detect that merger, its fair to say that it won't go unnoticed. The gravitational waves alone are sure to be impressive!