A couple of supermassive black holes found is discovered just 89 million light years away to Earth. The data indicate that the couple will merge into a single black hole within a period of about 250 million years.
Located in the constellation of aquarium, just 89 million light years away, the Galaxy NGC7727 has a distorted and strange appearance. Its various irregular filaments and plumes made it included in the ARP atlas of peculiar galaxies, where it was cataloged with the number 222. That is, the same Galaxy NGC7727 is also known as ARP222.
Its complex morphology indicates that NGC7727 is the collision product of two minor spiral galaxies. Indeed, during a galactic collision of this style, huge structures are created with forms of filaments or feathers (called 'tide queues') that are constituted by the billions of stars that were on the discs of the initial galaxies.
The collision process between large spiral galaxies may take billions of years, but the final result can be predicted by simulations performed with supercomputers. In the case of NGC7727, it is very possible that when the merger of the two initial galaxies is completed, the system is converted into a great elliptical galaxy (without arms) that has little material available to form new stars.
Each spiral galaxy has a supermassive black hole in its center. As NGC7727 seems to be the collision of two galaxies, in its central region two separate black holes were sought, each corresponding to each of the two galaxies they collided. One of them is very massive and has been known for a long time, but the second, which is much lower, has only been detected recently. It was three years ago, when a team coordinated by Francois Schweizer, using the Hubble Space Telescope, identified the second galactic core, confirming that the two initial galaxies were very different, one should have been much greater than his companion.
Now, an international team led by astronomer Karina Vogel (Observatory of Strasbourg) has obtained superb images of the two nuclei of NGC7727 and, studying the speeds of the stars of their surroundings, has been able to measure the masses of the seasons black holes that They contain both nuclei. The largest of them has a mass that is about 154 million times the sun, while the mass of the second is six solar masses.
The two black holes are separated by a distance of about 1600 light years. Of all known couples of black holes, this is the one that has the smallest separation between the two members. From their masses and their disposition, Vogel and collaborators estimate that the Grande will end up absorbing the little one in about 250 million years. The fusion of black holes pairs is a relatively common phenomenon in the universe that can be observed by detecting gravitational waves that are emitted at the time of collision. We already inform in these chronicles of the cosmos that this type of detection is carried out very systematically, since a few years ago, thanks to specialized observatories such as Ligo and Virgo.
Together with NGC7727, many galaxies are already known with double nuclei, which confirms that collisions between galaxies were relatively frequent at a certain era during the evolution of the universe. However, NGC7727 is a particularly interesting case, because being the closest to the land of acquaintances, it is possible to observe all the phenomenology of the collision with the greatest possible detail.
The measures carried out by Vogel and collaborators are an authentic observational feat that has been possible thanks to a complex instrument called Muse (Multi Unit Specroscopic Explorer) that is installed in one of the great VLT telescopes that has that in the Atacama desert, Chile .
With its eight-meter mirrors in diameter, these powerful telescopes are equipped with the most sharp technologies, so they have allowed measuring the rates of the stars at the immediate vicinity of each black hole with a dread detail. With adaptive optic techniques, which mitigate the effects of atmospheric turbulence, Muse obtains a spectrum for each pixel of only 0.025 seconds of arc of your field of vision. This high resolution power, along with the high sensitivity provided by the large size of the mirror, makes the VLT combination / muse an extremely capable instrument.
With 39 meters in diameter, the future Gran Telescope ELT, now under construction in Cerro Armazones (also in Atacama, Chile), will far exceed the VLT in the year 2027. The ELT will be equipped with the Harmoni spectrograph of high performance. In the design and construction of both ELT and Harmoni, several Spanish institutions and companies participate.
The Vogel Article and Collaborators, entitled First Direct Dynamical Detection of a Dual Super-Massive Black Hole System at Sub-KPC Separation has been published in a recent number of the Astronomy & Astrophysics magazine. The manuscript can be consulted in this link.
Rafael Bachiller is Director of the National Astronomical Observatory (National Geographic Institute) and academic of the Royal Academy of Doctors of Spain.Date Of Update: 11 December 2021, 01:31