Tuesday , March 9 2021

Black holes like to live in pairs

It is believed that most of the galaxy hides in its core a black hole with a mass of more than a million suns.

Of course, the Milky Way is no exception, and observation of the starwalking around the center of our galaxy has enabled us to calculate the mass of its central black hole, called Sagittarius A, in 4.3 million solar masses.

On the other hand, it is also noticed that many great galaxies are the result of joining two smaller galaxies. The universe is now 13.8 billion years old and we still see galaxies appear in our area, but this confusion between the galaxies was particularly common in the last period of the universe in the first billions of years when the space did not expand and the galaxies were closer to one second. friend.

When combined, each of the two original galaxies introduces their own black hole and slowly moves to the center of the new galaxy that is being built. Therefore, in all these galaxies, the result of the merger, you can expect a double black hole inside. And astronomers accumulate traces of the existence of such monster monsters. For example, the shape of spectral lines generated by gas emitted from the nucleus of the galaxy.

Giant plasma nozzles

But black holes can not be seen directly, and at this point, to detect these pairs, scientists must resort to indirect methods. One of the most impressive manifestations of the presence of the super-massive black hole is the ejection of proximity to large plasma jets at speeds close to the speed of light.

The plasma of these jets radiates mainly radio waves, and their image, obtained by radio telescopes, is among the most fascinating in the universe.

Plasma jets can stretch for millions of light years and are easy with a single black hole. But if there is another black holes in the neighborhood, it causes the nozzles to first bend or take more morphology, changing the direction of ejection from which originally came. In some cases, these changes in the direction may consist of precession: the jet can cyclically change the direction of the emission over a hundred thousand years.


Martin Krause from Hertfordshire University and Tasmania, Australia, along with the international astronomers group, studied the geometry of nozzles that triggered a group of active galaxies, selecting those that are not quite clear, pointing to the presence of double black holes. So far 33 of these galaxies have been watched, and 24 of them (73%) have shown some kind of curvature or straight line changes. For example, in the case of the Swan Galaxy, the jet is very different from its axis, which can be explained by the theoretical model of black holes that rotate one another around the age of 18.

These results, together with some other previously obtained groups, confirm that there is a very important population of double black holes in the largest galaxies. However, some astronomers point out that changes in the direction of the jet are not a definitive sign of binary holes. Specifically, there may be inclinations or irregularities in the disc sizing plate, which should exist around the super-massive black hole (the disc from which, ultimately, the jet energy continues) may also change the proper path for such plasma outbreaks.

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