"Phenomenal discovery": A black hole older than its galaxy
For the first time, mass of a supermassive black hole in the early cosmos could be determined thanks to a fortunate coincidence. Consequences are far-reaching.
Abell2744-QSO1 can be observed three times thanks to a gravitational lens
(Image: NASA, ESA, CSA, Lukas Furtak (Ben-Gurion University); Bildbearbeitung: Alyssa Pagan (STScI))
A research group has found a supermassive black hole in the early universe using the James Webb Space Telescope, which must have formed before its galaxy. The “remarkable finding,” as research lead Roberto Maiolino from the University of Cambridge calls it, “completely turns on its head the classical theories about how black holes form and grow.” Until now, it was generally assumed that galaxies must have formed first, and their massive stars provided the material for the formation of gigantic black holes. However, the analysis of the galaxy designated Abell2744-QSO1 (QSO1) now suggests that the opposite may have happened.
Visible three times
QSO1 is a truly prototypical “little red dot” galaxy, explains the research group; these unusual objects have been puzzling astronomers for some time. They are tiny, brightly shining, and strikingly red points of light from the early universe, and it was unclear whether they were galaxies or active black holes with dense gas shells. The James Webb Space Telescope sees QSO1 approximately 700 million years after the Big Bang; the object has a diameter of just 1300 light-years. However, thanks to a foreground gravitational lens, we see the “little red dot” three times in the night sky, making it an enormous stroke of luck for research.
To investigate the nature of the object and its composition, two doctoral students from the University of Florence used the James Webb Space Telescope's Near-Infrared Spectrometer (NIRSpec) to determine how the gas moves there. They found that it performs Keplerian motion, meaning it orbits a central point like the planets in the solar system. If the mass were more evenly distributed, this would not be the case, explains the team. With a total of 50 million solar masses, the supermassive black hole at the center of QSO1 accounts for two-thirds of its mass. A thousand times more than in comparable galaxies in the vicinity.
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Furthermore, the researchers found that the gas in QSO1 consists almost exclusively of hydrogen and helium. Heavier elements such as oxygen, which would be expected in galaxies with many stars and stellar remnants, were found only in very small amounts. Overall, it is one of the most primordial galaxies ever measured. Together, both results suggest that the black hole did not form slowly from stellar remnants that collapsed into stellar black holes. While it is still unclear exactly how it formed instead, it is almost certain that the black hole was “born large” and did not rely on a galaxy for its formation.
“This is a phenomenal result,” says Maiolino. Not only because the discovery could provide an answer to the nature of “little red dots” and the formation of the first supermassive black holes. It is also “the first direct measurement of a black hole mass within the first billion years after the Big Bang, and it is consistent with previous measurements.” This confirms previous methods and means that black hole masses in the early universe were not overestimated. The work is presented in two articles in the research journals Nature and in the Monthly Notices of the Royal Astronomical Society.
(mho)
