In the 1960s, astronomers began theorizing that there might be black holes in the Universe that are so massive – supermassive black holes (SMBHs) – they could power the nuclei of active galaxies (aka. quasars). A decade later, astronomers discovered that an SMBH existed at the center of the Milky Way (Sagitarrius A*); and by the 1990s, it became clear that most large galaxies in the Universe are likely to have one.
Since that time, astronomers have been hunting for the largest SMBH they can find, in the hopes that can see just how massive these things get! And thanks to new research led by astronomers from the Australian National University, the latest undisputed heavy-weight contender has been found! With roughly 34 billion times the mass of our Sun, this SMBH (J2157) is the fastest-growing black hole and largest quasar observed to date.
The team’s study, which recently appeared in The Monthly Notices of the Royal Astronomical Society, was led by Dr. Christopher A. Onken – the operations manager of the SkyMapper telescope. He was joined by researchers from the Research School of Astronomy and Astrophysics (RSAA) and the Center for Gravitational Astrophysics (CGA) at ANU, as well as the European Southern Observatory (ESO) and Steward Observatory.
The same team was responsible for discovering J2157, which they did back in 2018, using data from the Gaia observatory, the Wide-field Infrared Survey Explorer (WISE) space telescope, and the SkyMapper Southern Sky Survey. That particular study was led by Christian Wolf, a member of the Australian Research Council’s Centre of Excellence in All-sky Astrophysics (CAASTRO), who also participated in this latest study.
As they indicated at the time, J2157 is the brightest quasar observed in the known Universe to date, which they attributed to the presence of an SMBH at its center. What’s more, they were able to rule out the possibility that its luminosity was the result of gravitational lensing, where the presence of intervening galaxies and other massive objects were responsible for magnifying J2157’s brightness.
This was a strong possibility, given that light J2157 is visible 12.5 billion light-years from Earth, and therefor has to traverse a huge distance in space and time to reach us. For this latest study, Dr. Onken and the team relied on data from the ESO’s Very Large Telescope (VLT) in Chile to constrain the distance and mass of this SMBH at the core of J2157. As Dr. Onken said in a recent ANU press release, what they found was rather surprising:
“The black hole’s mass is also about 8,000 times bigger than the black hole in the center of the Milky Way. If the Milky Way’s black hole wanted to grow that fat, it would have to swallow two-thirds of all the stars in our Galaxy. We’re seeing it at a time when the universe was only 1.2 billion years old, less than 10 percent of its current age. It’s the biggest black hole that’s been weighed in this early period of the Universe.”
Already, the team had inklings that J2157 contained a rapidly-growing SMBH that consumed stars in the central region of its galaxy on a regular basis. But the fact that it was the fastest-growing SMBH in the Universe just 1.2 billion years after the Big Bang was nothing short of astounding. As Dr Fuyan Bian, a staff astronomer at the European Southern Observatory (ESO), said:
“We knew we were onto a very massive black hole when we realized its fast growth rate. How much black holes can swallow depends on how much mass they already have. So, for this one to be devouring matter at such a high rate, we thought it could become a new record holder. And now we know.”
But equally significant is what J2157 can teach us about the early Universe and its subsequent evolution. For some time, astronomers have been looking for more examples of SMBHs in the early Universe to see how they affected the evolution of galaxies and the cosmos as a whole. At the same time, they have been looking for answers as to how SMBHs could have grown so large in such a short space of time.
While these questions remain unresolved, the discovery of this ancient and most-massive of supermassive black holes could provide some very helpful clues. Already, the team behind this discovery is searching for more black holes that existed at the center of galaxies shortly after the Big Bang, in the hopes that they might find some additional clues.
Said team member Dr. Fuyan Bian, a staff astronomer at the European Southern Observatory (ESO):
“With such an enormous black hole, we’re also excited to see what we can learn about the galaxy in which it’s growing. Is this galaxy one of the behemoths of the early Universe, or did the black hole just swallow up an extraordinary amount of its surroundings? We’ll have to keep digging to figure that out.”
One of the most important developments in the fields of astronomy and astrophysics in the past few decades has been the ability to see farther and with greater clarity. By looking deeper into the cosmos, they have also been able to look farther back in time and see what the Universe looked like at a very young age. This has allowed scientists to test cosmological theories about how the Universe has grown and evolved ever since.
With all the new developments that expected in the ensuing years and decades – which include the deployment of next-generation telescopes, AI and machine learning, and increased data-sharing – scientists anticipate that the most enduring cosmological questions will soon be answered!