Companion of a supermassive black hole has generated previously unseen flares

Scientists have proved that the active galaxy OJ 287 contains two supermassive black holes: the main one and its companion. When the latter approaches the first and crosses its accretion disk, it creates flares of amazing power.

How flares occur in the center of OJ 287. Source: AAS 2018

Two black holes in the galaxy OJ 287

Scientists from a number of European universities and observatories have published a study on the active galaxy OJ 287. It has been known to astronomers since 1888. Already in the XX century, scientists have discovered that it is extremely active in the radio range and technically should be considered a quasar.

More than 40 years ago, astronomers from the University of Turku noticed that the activity of the galaxy in the radio range had a periodicity. There are two cycles, one lasting 12 years, and the second — 55. Then the fact about a black hole in the center of quasars was just one of the possible explanations. But even then, scientists suggested that in this case, there were two similar objects that orbited each other.

In this case, the shorter cycle was explained by the orbit of the smaller black hole around the larger one, and the longer one was explained by the displacement of its orbit. However, until the 2020s, this assumption was purely theoretical. It was not possible to separate two objects in the sky in any range. Only the change in the signal suggested that it was not there alone.

How to predict flares?

The system at the center of the galaxy OJ 287 consists of two black holes. Most of them have a mass 18 billion times larger than the Sun. The second one is at least a hundred times lighter than it. Therefore, although both of them are considered supermassive, in fact we are talking about a central object and a companion orbiting around it.

Scientists have long understood that the periodic amplification of the signal from OJ 287 is actually a series of powerful flares that occur when a smaller black hole dives into the accretion disk of a larger one at a speed close to light. At the same time, gas and dust turn into incandescent bubbles that remain hot and emit radio signals for several more months.

The flare that occurs is brighter than all the stars of the galaxy combined. They are quite regular, but it has been impossible to predict them until recently, because the orbit of the smaller of the black holes was not known. However, studies of flares carried out in 1983, 1994, 1995, 2005, 2007, 2015 and in 2019, it was allowed to calculate it.

Research results

In 2021-2022, scientists conducted a series of long-term observations of the OJ 287 center. They confirm that this is indeed a binary system of supermassive black holes, one of which dives into the accretion disk of the other and thereby causes large-scale flares in the radio range. 

However, it came as a surprise to scientists that the flares turned out to be more diverse than previously thought. In particular, a flare was recorded that was 100 times brighter than all the stars of the galaxy OJ 287 combined. However, it lasted only a day. Scientists believed that they saw how a smaller black hole received a portion of matter from a larger one and “swallowed” it, partially turning it into radiation.

The second flare was much longer, but was observed only by the Fermi gamma-ray telescope. Scientists convinced that it arose when relativistic jets from the poles of a smaller black hole intersected with the gas of the accretion disk of a larger one. It was this event that could lead to the birth of such high-energy waves.

According to

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