A team of astrophysicists from India discovered a rare merger of three supermassive black holes. When they observed the merger of two galaxies called NGC7733 and NGC 7734 near our celestial body, they found that the center of the latter emits unusual radiation, and they found a strange movement of a large bright cluster in it at a speed comparable to that of NGC7733.
Third one named as NGC7733N
Inferring that it is an independent galaxy, the scientists named it NGC7733N. There are millions of solar-mass supermassive black holes at the center of the galaxy, called active galactic nuclei. Because they “accumulate” substances, they generally emit light around them, which can be observed using spectroscopy.
The three merged black holes are part of the galaxy in the constellation Toucan. When you think that our closest neighboring galaxies, the Andromeda galaxy, are 2.5 million light years away, they are very far from us. However, the article describes them as nearby galaxies.
Statement by Jyoti Yadav; doctoral student of IIA
“In astronomy, everything is relative. When we study the solar system, we say that Mercury is closer and Jupiter is far away … Compared to our closest neighbor, the Andromeda galaxy, the galaxies NGC 7733, 7734 and 7733 N are pretty far away, but compared to the size of the universe, they are nearby galaxies, “said Jyoti Yadav, a doctoral student at the Indian Institute of Astrophysics and first author of the paper, published in the journal Astronomy and Astrophysics.
Apparatus used
The research used data from the Ultraviolet Imaging Telescope (UVIT) on the ASTROSAT, India’s first space observatory, the European Integrating Field Optical Telescope MUSE installed on the Chilean Very Large Telescope (VLT), and infrared images from the Optical Telescope (IRSF) in South Africa.
Email received by the Hindu from Mousumi Das
The author of the article said in an email to the Hindu’s, Mousumi Das of the Indian Institute of Astrophysics that they are studying the active galactic nuclei in the two huge barred spiral galaxies NGC7733 and NGC7734, and found the third. This galaxy is surprising. “It’s a bit like buying two and getting one free,” Dr. Das said. “The PI for this project uses spectral data from a European telescope called MUSE in Chile to confirm our suspicions.”
The astrophysicists observed these galaxies in South Africa
The team observed these galaxies with a near-infrared telescope in South Africa. “Then later, because they looked interesting, we also looked at them with UVIT [aboard ASTROSAT],” Dr. Das said. “We also found optical data in the MUSE file. So we don’t have to do spectral analysis.”
Statement by Press Information Office
In a statement from the Press Information Office, the team explained that if two galaxies collide, their black holes will also get closer by transferring kinetic energy to the surrounding gas. The distance between black holes will decrease over time, until the distance is about 1 second (3.26 light-years). The two black holes can no longer lose any kinetic energy in order to get closer and merge. This is called the trailing parsing problem.
The existence of a third black hole can solve this problem. “When another black hole or star passes by and takes away some of their combined angular momentum, the two can get closer,” explained Dr. Das. Thus, double-merger black holes merge with each other in the presence of the third.
Triple AGNs are extremely rare
Many pairs of active galactic nuclei (AGN, the supermassive black hole at the center of the galaxy) have been detected in the past, but triple AGNs are extremely rare, and only a few have been detected before observations from X-rays. “Multiple accretion black holes [AGN] may be more common in our universe, especially in clusters of galaxies. Therefore, the growth of black holes may be driven by this merging of clusters,” he said. This is only the third test of such a system.
“This work is surprisingly using several telescopes around the world (and one in space) to determine the existence of 3 AGN. In fact, the use of such multiple telescopes and observation bands is essential for good astronomical research. It also shows that astrophysics is a truly collaborative science,” said Preeti Kharb, who worked with the National Center for Radiological Astrophysics in Pune (NCRATIFR), who was not involved in the work.
