Competent astrophysicists universally agree that at the core of the vast majority of large galaxies, there exist compact objects containing at least one million, and sometimes several billion, solar masses that behave in accordance with the theory of black holes. While some uncertainties still persist, the existence of supermassive black holes has become a firmly established concept in astrophysics, even though surprises may emerge with the advent of gravitational waves or future images from the Event Horizon Telescope.
However, the formation of supermassive black holes remains a puzzle, although it is now believed that their growth primarily occurred through the accretion of matter from cold filaments.
Several hypotheses have been considered over the decades, with some gaining prominence due to recent observations. These hypotheses include the existence of primordial stars with very high masses and the production of giant black holes during the Big Bang.
One of these hypotheses has gained more credibility following joint observations in the infrared by the James-Webb Space Telescope and in the X-ray domain by the venerable Chandra space telescope, which has been in orbit since 1999.
This discovery has been published in Nature Astronomy and consists of three articles that are freely accessible on arXiv.
Abell 2744, a Gravitational Magnifying Glass for Discovering Distant Galaxies
The journey began with Chandra’s detection of an X-ray source in a galaxy called UHZ1, located in the direction of the Abell 2744 galaxy cluster, which is situated 3.5 billion light-years away from the Milky Way. Abell 2744 is also known as the Pandora Cluster, resulting from the merger of four smaller galaxy clusters and rich in dark matter. This leads to a gravitational lensing effect that astronomers have been using to magnify images of distant galaxies in both visible and near-infrared light.
Abell 2744 has previously been utilized in this manner with the Hubble telescope and more recently with the James-Webb. This time, it was revealed that UHZ1 was observed as it existed only 470 million years after the Big Bang. Data from Chandra show that the X-ray source associated with the galaxy exhibits all the characteristics of a supermassive black hole in active growth, marking it as the most distant X-ray-detected black hole ever.
The analysis of the data collected with James-Webb and Chandra indicates an unusual scenario. While there is typically a factor of 1,000 between the mass of a supermassive black hole and the mass of stellar matter in its host galaxy, it appears that the giant black hole in UHZ1, with its 10 to 100 million solar masses, contains as much matter as all the stars in the galaxy it inhabited during the distant past, as revealed by photons that have traveled for over 13 billion years.
A Direct Collapse of Clouds of Matter Into Giant Black Holes
The black hole was in an early growth stage never observed before, where its mass was similar to that of its host galaxy. More importantly, the observations now support the theory that supermassive black holes could form directly from the gravitational collapse of a massive cloud of matter.
One of the co-authors, Priyamvada Natarajan of Yale University, made theoretical predictions in 2017 that the black hole would have a large mass at a young age, as well as its X-ray emissions and the brightness of the galaxy that Webb detected. In summary, this discovery provides the first evidence of an “Outsize Black Hole” and the strongest proof to date that some black holes form from massive gas clouds. For the first time, we are witnessing a brief stage during which a supermassive black hole weighs approximately as much as the stars in its galaxy before ultimately surpassing them in mass.