These bodies form when stars reach the end of their life cycle, their outer layers explode, and they are so strong in gravity that nothing (not even light) can escape their surfaces.
It is also important because it allows astronomers to observe the laws of physics under the most extreme conditions. Periodically, this giant gravity will devour the stars and other objects in their vicinity, releasing huge amounts of light and radiation.
In October 2018, astronomers witnessed such an event when observing a Black hole In a galaxy 665 million light years from Earth.
While astronomers have witnessed events like this before, another team of Harvard and Smithsonian Center for Astrophysics I noticed something unprecedented when they examined the same black hole three years later.
As explained in a recent study, the black hole was shining so badly because it was ejecting (or “belching”) the remaining material from the star at half the speed of light. Their findings could provide new clues about how black holes feed and grow over time.
He was leading the team Yvette Sindiswho is a CfA Research Associate, was joined by an international team of researchers from Commonwealth Scientific and Industrial Research Organization (CSIRO), and Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), and Space Telescope Science Institute (STScI), and Columbia Astrophysics LaboratoryThe Flatiron Institute Center for Computational Astrophysicsand the University of California at Berkeley, Radboud University (Netherlands), and York University in Toronto.
The paper describing their findings recently appeared in Astrophysical Journal.
As they report in their paper, the team noted the rush while reviewing data on tidal disturbance events (TDEs) that have occurred over the past few years.
These occur when stars pass close to black holes and are broken up during multiple passes, a process known as “spaghettitation” because of how stars are torn apart into filaments.
In 2018, astronomers at Ohio State University noted that the TDE in question (dubbed AT2018hyz) as part of Automated scanning of the entire sky for supernovae (ASAS-SN).
Shortly thereafter, an international team examined the AT2018hyz at both visible and ultraviolet wavelengths using Automated scanning of the entire sky for supernovaeThe Fred Lawrence Whipple Observatoryand the UV Optical Telescope (UVOT) on Neil Geirels Swift Observatory.
This team was led by Sebastian Gomez, a postdoctoral fellow at the Space Telescope Science Institute and co-author of the new paper. As he explained, TDE was “unremarkable” at the time.
In June of 2021, Cendes and her colleagues examined it again using radio data from the Very Large Array (VLA) in New Mexico. To their surprise, they noticed that the black hole had mysteriously resurrected. As explained by Cendes in CfA press release:
“This totally surprised us – no one had ever seen anything like this before.
We applied for the principal’s estimated time on multiple telescopes, which is when you find something quite unexpected, you can’t wait for the regular cycle of telescope proposals to observe it. All requests were immediately accepted.”
The team then made follow-up observations of AT2018hyz using multiple telescopes and at multiple wavelengths. This included radio observations made with the VLA, and Atacama Large Millimeter Matrix (ALMA) in Chile meerkat In South Africa, the Australian Compact Telescope Group in Australia.
Combined with X-ray and gamma ray data obtained by space Chandra X-ray Observatory and Neil Geirels Swift Observatory (respectively).
according to Edo Burgera Harvard professor of astronomy and CfA and co-author of the new study, radio observations of TDE proved most striking:
“We’ve been studying TDE with radio telescopes for more than a decade, and we sometimes find that it shines in radio waves as it spews material out as a black hole first consumes the star.
But at AT2018hyz, there was radio silence for the first three years, and it’s now massively lit to become one of the brightest wireless TDEs ever.”
The team concluded that this was caused by the black hole ejecting the remaining material from the star at relativistic velocities (a fraction of the speed of light).
This is the first time astronomers have observed such a phenomenon, and the team is unsure why the outflow was delayed by several years.
TDEs are notorious for emitting light as they occur as the squiggly material from the star becomes elongated around the black hole and heats up, creating a flash that astronomers can see millions of light-years away.
In some cases, spaghetti will be sent back into space, which astronomers have likened to black holes as “chaotic eaters.” However, outflow emissions usually develop rapidly after a TDE occurs rather than years later.
In short, it’s as if this black hole suddenly started burping out a bunch of stellar material that it ate years ago, said Sendez.
Moreover, these “burps” were very energetic, with the ejected material speeding up to 50 percent of the speed of light — about five times what astronomers have observed with other TDEs. Happy Burger:
“This is the first time we’ve seen such a long delay between feeding and outflow. The next step is to explore whether this really occurs more regularly and we haven’t been looking at TDE late enough in its development.”
These findings, along with observations of similar events, will help astronomers better understand the feeding behavior of black holes. This, in turn, could provide insight into how they grew and evolved over time and their role in the evolution of the galaxy.