James Webb discovers oldest collision of giant black holes: Why is this finding important?

Science and culture 18 May, 2024 11:17

In a paper published on Thursday in The Monthly Notices of the Royal Astronomical Society, a group of astronomers reported that they had discovered the earliest known collision of supermassive black holes. This merger of colossal objects occurred 740 million years after the Big Bang. This finding proves that black holes have played a significant role in the evolution of galaxies from the very beginning and explains their rapid growth in ancient times.

With the advent of the incredibly sensitive James Webb Space Telescope, which operates in the infrared range, astronomers have been able to observe phenomena in the early Universe that previous instruments could not detect. This period is when the Universe had not yet reached its first billion years out of its current approximate age of 13.8 billion years, Space.com reports.

One of the mysteries of the early Universe is the discovery of numerous supermassive black holes before it reached its first billion years. According to our theories, these objects should not have had enough time to develop detectable masses ranging from tens of millions to billions of solar masses. These processes should take billions of years, not hundreds of millions, as the Webb data suggests. The new observation explains how black holes could quickly gain mass in ancient times, through mergers that should not have been so numerous back then to influence the subsequent evolution of galaxies and the Universe itself. It seems earthly science was mistaken in this regard.

"Our results show that merging is an important way for black holes to grow rapidly even at the dawn of the cosmos," said Hannah Übler, the study leader and a scientist at the University of Cambridge, in a statement. "Along with other Webb discoveries of active massive black holes in the distant Universe, our results also show that massive black holes shaped the evolution of galaxies from the very beginning."

In fact, the researchers detected signs of activity from an ancient quasar—the active center of galaxy ZS7, where a supermassive black hole resides and feeds rapidly. The Webb's spectral sensitivity was sufficient to see two components in the object's radiation. Both turned out to be supermassive black holes on the brink of merging. This was indicated by the intense radiation from the heated gas in the black holes' accretion disks and the analysis of the density of ionized gas.

The mass of one of the objects was determined with sufficient accuracy—it was 50 million solar masses. The mass of the second black hole is estimated to be about the same, but scientists could not determine it precisely due to the dense gas cluster in the path of the radiation.

"The stellar mass of the system [galaxy ZS7] we studied is similar to the mass of our neighbor, the Large Magellanic Cloud," the scientists explain. "We can try to imagine how the evolution of merging galaxies would be affected if each galaxy had one supermassive black hole as large as the one in our Milky Way." Thus, astronomers hint that our models of galaxy evolution clearly do not account for many aspects of their behavior at the dawn of their existence, and this needs further investigation.