At the center of almost every galaxy lies a giant monster: a supermassive black hole that is ten of thousands or even millions of times the mass of the sun. But not all of these monsters are the same: some are sedate and quiet, while others are active and are rapidly gobbling up material around them. Now, astronomers are getting a close look at a black hole that is “waking up” and going from a dormant state to an active one as it starts chowing down on nearby matter.
The black hole at the heart of galaxy SDSS1335+0728, located 300 million light-years away, was quiet for decades as it consumed little matter and was in a dormant state. But recently it suddenly lit up and began spewing out X-rays as it woke up and started feeding.
Astronomers have been watching the black hole using a European Space Agency (ESA) telescope called XMM-Newton, as well as NASA’s NICER, Chandra and Swift telescopes.
“This rare event provides an opportunity for astronomers to observe a black hole’s behavior in real time, using X-ray space telescopes,” said lead researcher Lorena Hernández-García of Valparaiso University. “This phenomenon is known as a quasiperiodic eruption, or QPE. QPEs are short-lived flaring events. And this is the first time we have observed such an event in a black hole that seems to be waking up.”
The bright center of this galaxy has been nicknamed “Ansky,” and astronomers have been observing it since 2019. They still don’t know what causes a black hole to switch on like this, and it’s a rare opportunity to study a black hole coming out of its slumber — and this one is especially powerful.
“The bursts of X-rays from Ansky are ten times longer and ten times more luminous than what we see from a typical QPE,” said fellow researcher Joheen Chakraborty of the Massachusetts Institute of Technology. “Each of these eruptions is releasing a hundred times more energy than we have seen elsewhere. Ansky’s eruptions also show the longest cadence ever observed, of about 4.5 days. This pushes our models to their limits and challenges our existing ideas about how these X-ray flashes are being generated.”
Black holes typically give off X-rays because the matter swirling around them, in a region called the accretion disk, gets extremely hot. But these bursts of energy are so strong that they suggest something different is happening: perhaps an object like a star or a smaller black hole is being yanked into the accretion disk and causing a shock wave in the surrounding material, creating a burst of X-rays.
The researchers hope that by continuing to observe the way that Ansky evolves, they can get more information over time. “For QPEs, we’re still at the point where we have more models than data, and we need more observations to understand what’s happening,” said ESA Research Fellow and X-ray astronomer, Erwan Quintin.
“We thought that QPEs were the result of small celestial objects being captured by much larger ones and spiraling down towards them. Ansky’s eruptions seem to be telling us a different story.”
The research is published in the journal Nature Astronomy.