Astronomers are observing a supermassive black hole that could be the center of another galaxy 300 million light-years away. In 2019, ultraviolet, infrared, and visible light began to emanate from it. Ars Technica writes about this in its article.

In February of this year, the galaxy began to emit X-rays, and it is becoming more active. Astronomers believe that this is an active galactic nucleus (AGN), which receives energy from supermassive black holes in the center of the galaxy and/or from the rotation of the black hole.

This conclusion was reached by the authors of a new article accepted for publication in the journal Astronomy and Astrophysics, although the authors acknowledge the possibility that it could also be some kind of rare event when a black hole ejects part of the mass of an absorbed star.

This burst of light was given the code name SDSS1335_0728. The Zwicky Transient Facility telescope was the first to detect it in the constellation Virgo.

The supermassive black hole in this constellation is estimated to be about 1 million solar masses. To better understand what might be going on, the authors analyzed archival data and combined it with the new observations.

There are many reasons why a normally quiet galaxy can suddenly burst into flames. This can happen due to supernovae or due to ejections from black holes. Such an ejection can form an accretion disk around the black hole, which emits powerful X-rays and visible light.

But these events do not last for almost five years, usually no more than a few hundred days.

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Therefore, the authors concluded that the galaxy has woken up and now has an active galactic nucleus. And the radiation is the result of the glow of cold dust and gas surrounding the black hole, which can form orbiting accretion disks. Gravitational forces compress the matter in the disk and heat it up to millions of degrees Kelvin, creating radiation across the electromagnetic spectrum.

But scientists do not rule out that this could still be a black hole ejection. If so, it will be the longest and weakest one detected so far. Or it could be a completely new and unexplored phenomenon.

So, SDSS1335_0728 is a galaxy worth watching. Astronomers are already preparing for further observations with the Multichannel Spectroscopic Explorer (MUSE) and the Very Large Telescope (VLT), and possibly even the Vera Rubin Observatory in Chile, which is scheduled to launch next summer.

Its Large Synoptic Survey Telescope (LSST) will be able to continuously image the entire southern sky, potentially capturing even more galaxy awakenings.

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There is also a supermassive black hole (Sgr A*) in the center of our galaxy, but it has not yet accumulated enough material for astronomers to detect any radiation, even in the infrared.

Consequently, its galactic core is considered inactive. It may have been active in the past, and it is possible that it will wake up again in a few million or even billions of years when the Milky Way merges with the Andromeda Galaxy and their supermassive black holes merge.