The most distant supermassive black hole ever found holds secrets to the early Universe
We’re seeing how it looked when the Universe was a toddler
Astronomers have spotted the most distant supermassive black hole ever seen in our Universe — a behemoth that’s nearly a billion times more massive than our Sun. This is no ordinary black hole either, but an active one known as a quasar that’s surrounded by a super bright, highly energetic disk of swirling gas and dust. And its discovery could help scientists learn more about what conditions were like when the Universe was still quite young.
The object — detailed in studies published today in Nature and the Astrophysical Journal Letters — gives us a great snapshot of the past. It’s so far away that its light has taken around 13.1 billion years to reach us. And since the Big Bang is thought to have occurred 13.8 billion years ago, astronomers are seeing this black hole as it looked when the Universe was just 690 million years old. On the cosmological timescale, that’s basically when the Universe was a mere toddler.
Scientists aren’t quite sure when the first stars formed after the Big Bang, but studying the gases in this quasar can tell us a bit about how the Universe was evolving at that time. And the search is still on to find more distant quasars, possibly ones that existed at an even earlier time. The more quasars we find, the better portrait astronomers can paint of the early Universe.
“Already we can learn a lot about the early Universe with this one, but of course you want more,” Bram Venemans, a black hole researcher at the Max Planck Institute for Astronomy who was part of the quasar’s discovery, tells The Verge.
Quasars make up the centers of massive galaxies and they’re thought to be some of the most luminous objects in the Universe. The black holes within them don’t actually emit any light, but the surrounding gas and dust churn so fast and create so much friction that they give off a ton of light and heat. However, it’s basically impossible to see the visible light from these objects, since quasars are super far away from Earth.
That’s why astronomers look for quasars in the infrared or near-infrared — light with wavelengths much longer than that of visible light that can be picked up with specialized telescopes. By studying this light, scientists can figure out just how far away a quasar is. Since the Universe is expanding, distant quasars are moving away from Earth, causing their light to stretch into even longer wavelengths and get “redder.” It’s a concept known as redshift, and it can tell us which quasars are farther out than others. The more distant an object is, the faster it appears to be moving away from us and the more its light has shifted toward the red end of the spectrum.
Finding the most far out quasars has been a multi-year process for Venemans and his team, including Eduardo Bañados of the Carnegie Institution for Science. They estimate that there are just 20 to 100 quasars at these incredibly extreme distances across the entire sky. Given the sheer amount of bright objects in the Universe, it makes the search long and tedious: the researchers spent many years combing through data from telescopes that have surveyed the stars, looking for candidates that might be super-distant quasars. Complicating matters is that sometimes, stars known as brown dwarfs can actually look pretty similar to quasars — but many of these objects reside in our own galaxy.
Ultimately, Bañados found a number of candidates he thought could be distant quasars and then analyzed them further with the Magellan telescopes in Chile to find this latest object. Up until this point, the farthest quasar that had ever been found was observed 13 billion light-years away, so it looked as it did when the Universe was 750 million years old. That’s only a 60-million-year difference gap between this newly discovered quasar. But at that time, 60 million years was just 10 percent of the age of the Universe. “Things were changing very rapidly,” Bañados tells The Verge.
In fact, astronomers believe this latest quasar was around when the Universe was going through a pivotal transition period. For hundreds of millions of years after the Big Bang, the Universe was a fairly boring place, a time often referred to as the Dark Ages. There weren’t any stars or black holes, but instead a bunch of dark matter, as well as hydrogen and helium spread throughout. Eventually these basic elements would collapse in on themselves and come together to form the first stars. And those stars would generate a bunch of radiation, stripping the electrons off the surrounding hydrogen in the Universe. It was a key moment in the Universe’s history known as the Epoch of Reionization, in which the hydrogen shifted from being neutral to ionized — and brought the Dark Ages to an end.
However, scientists aren’t quite sure when this shift happened. They think it started around 500 million years after the Big Bang and finished up when the Universe was 1 billion years old — but it’s been difficult to narrow down the exact timeline. Now this quasar is providing some answers. By studying the light from this object, the astronomers found that much of the hydrogen around the quasar was still neutral. So they believe that this quasar existed right in the middle of the Epoch of Reionization.
There are still some aspects of this quasar that puzzle astronomers, though. For instance, it’s curious how a quasar this massive could have even existed back then. It takes quite a long time for black holes to acquire enough material to grow so big, and astronomers originally thought the process would have taken longer than 690 million years. That’s why the astronomers plan to keep searching for distant quasars like this one to better understand what was around back then. “The expectation is they shouldn’t be there but now we know that there’s at least one,” says Bañados, adding, “that’s really difficult for black hole models to explain.”