A pair of black holes, closest to Earth’s ‘just before impact’, have been discovered

▲ This image shows two bright galactic nuclei in the galaxy NGC 7727, located 89 million light-years from Earth, in close-up (left) and wide (right) images. At the center of each nucleus is a supermassive black hole. Photo=ESO/Voggel et al., ESO/VST ATLAS

Among the black holes discovered so far, a pair of black holes closest to Earth have been discovered. What’s more, the pair of black holes, which will soon become one just before the collision, turns out to be supermassive black holes lurking in a nearby galaxy.

The two black holes are gravitationally dancing with each other at the center of galaxy NGC 7727, about 89 million light-years from Earth in the constellation of Aquarius. Scientists have never seen such a pair of black holes so close on our planet, but it is also the first time seeing two black holes so close to each other.

The black hole couple, which will merge into one massive black hole in about 250 million years from now, has not been detected for a long time because it doesn’t emit much X-ray radiation, the usual evidence of black hole existence. The discovery of the black hole was aided by a collaboration between a powerful pair of telescopes, the European Southern Observatory’s (ESO) extra-large telescope in Chile and the Hubble Space Telescope.

“This is the first time that two supermassive black holes have been found so close to each other at less than half the distance from previous records,” said Karina Vogel, the study’s lead author and astronomer at the Strasbourg Observatory in France.

Previous records of the closest known black hole couple are 470 million light-years from Earth, making them more than five times more distant than the newly discovered pair of black holes.

▲ As a result of the analysis, the large black hole has a mass close to about 154 million times that of the Sun, and its companion black hole has a mass of about 6.3 million times that of the Sun. (Photo=ESO)

Thanks to the close proximity of the pair of NGC 7727 black holes, for the first time astronomers were able to determine the masses of the two black holes by measuring the effect of each other’s gravitational pull on a nearby star. Among them, the large black hole has a mass close to about 154 million times that of the Sun, and its companion black hole has a mass of about 6.3 million times that of the Sun.

Supermassive black holes are usually located at the centers of large galaxies, and when two galaxies collide and merge, so do black holes.

Scientists believe the findings not only provide a glimpse into the formation of supermassive supermassive black holes, but also suggest that more black holes and merging pairs may be lurking in other nearby galaxies.

“Our findings suggest that there may be many more of these artifacts of galactic mergers, and that there may still be many hidden giant black holes,” Vogel said. We can increase it,” he added.

Scientists now expect the completion of ESO’s ELT (Supergiant Telescope) in northern Chile, expected in 2024, will further spur the search for supermassive black holes and black hole pairs in the next few years.

ESO astronomer Steffen Mieske, co-author of the discovery, said: “Using ELT’s HARMONI (high-angle resolution monolithic optics and near-infrared field spectroscopy) will allow us to detect much further away than we have today.” The discovery was published on November 30 (local time) in the journal Astronomy and Astrophysics.

Columnist Lee Kwang-sik [email protected]


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