Astronomers have detected and measured one of the largest black holes ever observed, using a new technique that should reveal more about the thousands of these cosmic giants expected to be discovered in the coming years.
This supermassive black hole has a mass equivalent to more than 30 billion times that of the Sun, according to the study published this week in a scientific journal of the British Royal Astronomical Society. It is the first whose characteristics are determined thanks to the gravitational lens detection technique.
This phenomenon is caused by the presence of an object so massive — a galaxy or a supermassive black hole — that it bends spacetime. Light coming from a distant source, therefore, appears distorted when passing close by. But while we can see a galaxy, we literally cannot see a black hole. This cosmic object has the particularity of being so dense that not even light can escape, which makes it invisible.
This time, the astronomers were “very lucky”, explained to the agency France-Presse (AFP) James Nightingale, astronomer at the University of Durham, in the United Kingdom, and first author of the study. These managed to observe the light of a galaxy located far behind the black hole, and whose path seemed to be deviated by the black hole, about two billion light years from Earth.
Most galaxies are said to have a black hole at their center, but until now, to detect their presence it was necessary to observe the energy emissions they produce when absorbing matter that ventured too close, or by observing their influence. in the trajectory of the stars that orbit around it. These techniques, however, only work for black holes close enough to Earth.
The gravitational lensing technique allows astronomers to “discover black holes in 99% of galaxies currently inaccessible” to traditional observation, because they are very distant, underlined the astronomer. There are around 500 gravitational lenses, but “this picture is about to change dramatically”, according to James Nightingale.
The European Space Agency’s Euclid mission, due to launch in July, will usher in “an era of ‘big data’ [megadados]” for black hole hunters, creating a high-resolution map of part of the Universe, added the scientist. According to Nightingale, in six years of observation, Euclid will be able to detect up to 100,000 gravitational lenses, including potentially several thousand black holes.
The discovery made by the astronomer and colleagues was based on computer simulations and images taken by the Hubble Space Telescope. These observations confirm and explain simulations carried out 18 years ago by an astronomer at the University of Durham and James Nightingale’s colleague, Alastair Edge, who suspected the presence of a black hole at the center of the galaxy Abell 1201.