Black holes prefer to live in couple

The astronomer Rafael Bachiller us discover in this series of phenomena, most spectacular of the Cosmos. Topics of throbbing research, adventures in astronomica

Black holes prefer to live in couple

The astronomer Rafael Bachiller us discover in this series of phenomena, most spectacular of the Cosmos. Topics of throbbing research, adventures in astronomical and scientific developments over the Universe analyzed in depth.

The curvature of the jets and gigantic that emerge from the cores of galaxies reveals the presence of numerous pairs of supermassive black holes.

Mergers of galaxies

it Is thought that most galaxies lurks at its core a black hole with mass exceeding a million solar masses. Of course the Milky Way is not an exception and, in fact, recently, the observation of the trajectories of stars orbiting around the center of our galaxy has allowed to calculate at 4.3 million solar masses mass of its central black hole, called Sagittarius A*.

class="icon-foto_16_g"> Precession in the jets of a radio galaxy Martin Krause

The jets can extend over millions of light years and they are well straight when they are created by a black hole simple. But if there is a second black hole in the vicinity, this makes the jets of the first bend or to adopt morphologies with multiple, altering the direction of ejection with that initially. In some cases, these changes of direction may consist of a precession: the jet may change its direction of ejection of cyclic form, with a period of the order of hundreds of thousands of years. And this precession creates a characteristic morphology in maps of the radio galaxies (see attached figure).


Martin Krause from the Universities of Hertfordshire (Uk) and Tasmania (Australia), along with an international group of astronomers has been studying the geometry of the jets were ejected by a set of active galaxies looking for those that are not perfectly rectilinear, which would betray the presence of black holes doubles. Up to now have been observed 33 of these galaxies, and the jets 24 of them (73 %) show some kind of curvature or alter the straight trajectories. For example, in the case of the galaxy Cygnus-A, the jet is well separated from its axis, which could be explained with a theoretical model of a pair of black holes that orbit each other with a period of 18 years.

These results, together with some other previously obtained by other groups, confirm that there is a population which is very important of black holes binaries in larger galaxies. However, some astronomers suggest that the changes in the direction of a jet are not a sign unique of a hole binary. In particular, the possible tilt or irregularities in the accretion disk should exist around a supermassive black hole (disk of the that, in last instance, it is appropriate to the energy of the jets) could also alter the trajectory, rectilinear and of such ejections of plasma.

Recreation a couple of black holes LIGO

To conclude strongly on the existence of those monstrous pairs of black holes, astronomers have put the hope in the possible detection of gravitational waves must be issued in accordance with the general theory of relativity of Einstein. These deformations of space-time have already been detected when it occurs the merger of two stellar-mass black holes. Those holes little mass are emitting intense gravitational waves due to the high speeds with which they orbit. The supermassive black holes orbit each other at speeds much lower and its emission gravitational is less intense, but perhaps in the near future when gravitational wave detectors have a greater sensitivity - perhaps to reach to be detected.

The article of Krause and co-workers, entitled "How Frequent Are Close Supermassive Binary Black Holes in Powerful Jet Sources?" will be published in the issue of January 1, 2019, of the british journal Monthly Notices of the Royal Astronomical Society. The manuscript can be found here.

Rafael Bachiller is the director of the National Astronomical Observatory (National Geographical Institute) and academic of the Real Academy of Doctors of Spain.

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Updated Date: 14 November 2018, 20:00



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