Friday, January 28, 2022

ESO Telescope Discovers Closest Pair of Supermassive Black Holes Yet

Using the European Southern Observatory’s Very Large Telescope (ESO’s VLT), astronomers have revealed the closest pair of supermassive black holes to Earth ever observed. The two objects also have a much smaller separation than any other previously spotted pair of supermassive black holes and will eventually merge into one giant black hole. Located in the galaxy NGC 7727 in the constellation Aquarius, the supermassive black hole pair is about 89 million light-years away from Earth. Although this may seem distant, it beats the previous record of 470 million light-years by quite some margin, making the newfound supermassive black hole pair the closest to us yet.  

Close-up view of the two bright galactic nuclei, each housing a supermassive black hole, in NGC 7727, a galaxy located 89 million light-years away from Earth in the constellation Aquarius. Each nucleus consists of a dense group of stars with a supermassive black hole at its center. The two black holes are on a collision course and form the closest pair of supermassive black holes found to date. It is also the pair with the smallest separation between two supermassive black holes — observed just 1600 light-years apart in the sky. The image was taken with the MUSE instrument on ESO’s Very Large Telescope (VLT) at the Paranal Observatory in Chile.
Close-up view of the two bright galactic nuclei, each housing a supermassive black hole, in NGC 7727, a galaxy located 89 million light-years away from Earth in the constellation Aquarius. Each nucleus consists of a dense group of stars with a supermassive black hole at its center. The two black holes are on a collision course and form the closest pair of supermassive black holes found to date. It is also the pair with the smallest separation between two supermassive black holes — observed just 1600 light-years apart in the sky. The image was taken with the MUSE instrument on ESO’s Very Large Telescope (VLT) at the Paranal Observatory in Chile. (Image: Voggel et al via ESO)

Supermassive black holes lurk at the center of massive galaxies and when two such galaxies merge, the black holes end up on a collision course. The pair in NGC 7727 beat the record for the smallest separation between two supermassive black holes, as they are observed to be just 1600 light-years apart in the sky. Karina Voggel, an astronomer at the Strasbourg Observatory in France and lead author of the study published in Astronomy & Astrophysics, said:

“It is the first time we find two supermassive black holes that are this close to each other, less than half the separation of the previous record holder.”

Supermassive black holes formed by merging of smaller black holes

Co-author Holger Baumgardt, a professor at the University of Queensland, Australia, said the merging of black holes like these could explain how the most massive black holes in the Universe come to be, adding:

“The small separation and velocity of the two black holes indicate that they will merge into one monster black hole, probably within the next 250 million years.”

Voggel and her team were able to determine the masses of the two objects by looking at how the gravitational pull of the black holes influences the motion of the stars around them. The bigger black hole, located right at the core of NGC 7727, was found to have a mass almost 154 million times that of the Sun, while its companion is 6.3 million solar masses. It is the first time the masses have been measured in this way for a supermassive black hole pair.

Just as people at a busy crossroad may accidentally bump into each other, so too can galaxies in the Universe! But in this case, the outcome is more dramatic than a small nudge. When two galaxies clash, they merge into each other, giving birth to a new, bigger one. One example is the NGC 7727 galaxy, shown in this image from ESO’s VLT Survey Telescope (VST) in Chile. Located 89 million light-years away from Earth in the constellation Aquarius, NGC 7727 is believed to be the result of a clash between two galaxies that occurred about one billion years ago. The consequences of this tremendous cosmic bump are still evident in the peculiar, irregular shape of NGC 7727 and the streams of stars in its outer regions. The image was taken in visible light as part of the VST-ATLAS survey. The goal of the survey is to map a vast region of the Southern Sky — so large you could fit about 19,000 full moons in it! By studying the galaxies in this region, astronomers aim to shed new light on the nature of dark energy, the mysterious force permeating the Universe and causing its accelerating expansion. (Image: via ESO / VST ATLAS team. Acknowledgment: Durham University / CASU / WFAU)

This feat was made possible thanks to the close proximity of the system to Earth and the detailed observations the team obtained at the Paranal Observatory in Chile using the Multi-Unit Spectroscopic Explorer (MUSE) on ESO’s VLT, an instrument Voggel learned to work with during her time as a student at ESO. Measuring the masses with MUSE, and using additional data from the NASA/ESA Hubble Space Telescope, allowed the team to confirm that the objects in NGC 7727 were indeed supermassive black holes.

Astronomers suspected that the galaxy hosted the two black holes, but they had not been able to confirm their presence until now since we do not see large amounts of high-energy radiation coming from their immediate surroundings, which would otherwise give them away, Voggel said:

“Our finding implies that there might be many more of these relics of galaxy mergers out there and they may contain many hidden massive black holes that still wait to be foundIt could increase the total number of supermassive black holes known in the local Universe by 30 percent.”

The search for similarly hidden supermassive black hole pairs is expected to make a great leap forward with ESO’s Extremely Large Telescope (ELT), set to start operating later this decade in Chile’s Atacama Desert. Co-author Steffen Mieske, an astronomer at ESO in Chile and Head of ESO Paranal Science Operations, concluded:

“This detection of a supermassive black hole pair is just the beginningWith the HARMONI instrument on the ELT we will be able to make detections like this considerably further than currently possible. ESO’s ELT will be integral to understanding these objects.”

Provided by: European Southern Observatory [Note: Materials may be edited for content and length.]

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Troy Oakes
Troy was born and raised in Australia and has always wanted to know why and how things work, which led him to his love for science. He is a professional photographer and enjoys taking pictures of Australia's beautiful landscapes. He is also a professional storm chaser where he currently lives in Hervey Bay, Australia.
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