Orbital telescopes detect increased activity from the supermassive black hole at the heart of the Milky Way

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Top: NASA graphic displaying an artists representation of G2 passing Sgr A* and prompting an X-ray flare. Bottom: An image of the region captured by NASA's Chandra X-ray Observatory(Credit: NASA/CXC/MPE/G/M. Weiss)

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Three space-based observatories appear to have picked up an unusual increase in activity from the supermassive black hole located at the center of our galaxy. According to the data, the black hole known as Sagittarius A* (Sgr A*), which has a mass of roughly 4 million times our Sun, is throwing out ten times the usual amount of bright X-ray flares.

The discovery was made by scientists analyzing data from NASA's WISE telescope and Chandra X-ray Observatory, combined with ESA's XMM-Newton platform. The telescopes had previously undertaken a long term observation campaign of the region in an attempt to better understand the monster lurking at the heart of the Milky Way.

The results of the study, which drew on data collected over a 15 year span, showed that, under normal circumstances, Sgr A* would be expected to give off a single bright X-ray flare around once every 10 days. However, for the past year the leviathan black hole has been recorded giving off X-ray flares at ten times the standard rate, with one flare being emitted every day.

We know that the flares are the result of superheated gas being drawn into a black hole. The question then becomes, what is the source of this extra gas? Our current understanding of black holes is still relatively rudimentary, leaving scientists unable to pin down exactly what is causing the increase in activity. The two leading theories on the increased emissions involve the passing of a body known as G2, and an increase in intensity of the stellar wind from huge stars nearby, forcing larger quantities of material toward the black hole and increasing the monster's feeding rate.

It was initially assumed that G2 was simply a mass of dust and gas. However, observations of the body after passing Sgr A* do not exhibit the levels of distortion that would be expected of such a body passing by a supermassive black hole. It has since been suggested that G2 is in fact the extended cocoon of a large star, the gravity of which kept much of the surrounding gas and dust from being siphoned off into Sgr A*.

Astronomers had first believed that the close proximity pass of G2 had no effect on the black hole, however further analysis of data from the orbital assets revealed that it was relatively soon after the passing of G2 that the brightness and frequency of the flares increased.

The observations back the idea that material stripped away from the passing cloud could theoretically be responsible for the increase in bright X-ray emissions, though it could still be the result of a cosmic coincidence.

"It’s too soon to say for sure, but we will be keeping X-ray eyes on Sgr A* in the coming months," states co-author of a paper on the research, Barbara De Marco of the Max Planck Institute for Extraterrestrial Physics in Germany. "Hopefully, new observations will tell us whether G2 is responsible for the changed behavior or if the new flaring is just part of how the black hole behaves."

The preprint of a paper on the findings can be found on the Cornell University page prior to its upcoming publication in the Monthly Notices of the Royal Astronomical Society.

Source: NASA

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