Astronomers have discovered the biggest explosion seen in the universe, a gargantuan event originating from a super-massive black hole in a cluster of galaxies 390 million light-years away, blasted a crater in the hot gas that could hold 15 Milky Ways. The event in the Ophiuchus galaxy cluster was five times bigger than the previous record-holder.
“In some ways, this blast is similar to how the eruption of Mt. St. Helens in 1980 ripped off the top of the mountain,” said Simona Giacintucci of the Naval Research Laboratory in Washington, DC, and lead author of the study. “A key difference is that you could fit fifteen Milky Way galaxies in a row into the crater this eruption punched into the cluster’s hot gas.”
Astronomers used NASA’s Chandra X-Ray Observatory, the XMM-Newton,Murchison Widefield Array and Giant Metrewave Telescope,, to make the discovery from images of the Ophiuchus galaxy cluster revealed an unusual curved edge. The scientists at first ruled out an eruption given the implausible amount of energy that would have been needed to carve out such an immense cavity in the gas cloud, says lead author Giacintucci. But the two space observatories, along with radio data from telescopes in Australia and India, confirmed that the curvature was, indeed, part of a cavity.
Chandra observations reported in 2016 first revealed hints of the giant explosion in the Ophiuchus galaxy cluster. Astrophysicist Norbert Werner and colleagues reported the discovery of an unusual curved edge in the Chandra image of the cluster. They considered whether this represented part of the wall of a cavity in the hot gas created by jets from the supermassive black hole. However, they discounted this possibility, in part because a huge amount of energy would have been required for the black hole to create a cavity this large.
The latest study by Giacintucci and her colleagues show that an enormous explosion did, in fact, occur. First, they showed that the curved edge is also detected by XMM-Newton, thus confirming the Chandra observation. Their crucial advance was the use of new radio data from the MWA and data from the GMRT archives to show the curved edge is indeed part of the wall of a cavity, because it borders a region filled with radio emission. This emission is from electrons accelerated to nearly the speed of light. The acceleration likely originated from the supermassive black hole.
“The radio data fit inside the X-rays like a hand in a glove,” co-author Maxim Markevitch of NASA’s Goddard Space Flight Center in Maryland, said in a statement. “This is the clincher that tells us an eruption of unprecedented size occurred here.” More observations are needed in other wavelengths to better understand what occurred, according to the team.
The black hole eruption must have finished because the researchers do not see any evidence for current jets in the radio data. This shutdown can be explained by the Chandra data, which show that the densest and coolest gas seen in X-rays is currently located at a different position from the central galaxy. If this gas shifted away from the galaxy it will have deprived the black hole of fuel for its growth, turning off the jets.
This gas displacement is likely caused by “sloshing” of the gas around the middle of the cluster, like wine sloshing around in a glass. Usually the merger of two galaxy clusters triggers such sloshing, but here it could have been set off by the eruption.
One puzzle is that only one giant region of radio emission is seen, as these systems usually contain two on opposite sides of the black hole. It is possible that the gas on the other side of the cluster from the cavity is less dense so the radio emission there faded more quickly.
In the labeled image above of the center of the Ophiuchus cluster shows the supermassive black hole. Researchers have traced the source of this gigantic eruption to jets that blasted away from the black hole and carved out a large cavity in the hot gas. Radio emission from electrons accelerated to almost the speed of light fills this cavity, providing evidence that an eruption of unprecedented size took place.
A cross in this labeled image gives the location of the central galaxy. The publicly-available infrared data, which show the stars and galaxies in the field of view, are not sensitive enough to reveal the galaxy. Even with higher quality data the galaxy would still not be visible in this composite image because it overlaps with bright X-ray and radio emission surrounding it.
“As is often the case in astrophysics we really need multiwavelength observations to truly understand the physical processes at work,” said Melanie Johnston-Hollitt, a co-author from International Center for Radio Astronomy in Australia. “Having the combined information from X-ray and radio telescopes has revealed this extraordinary source, but more data will be needed to answer the many remaining questions this object poses.”
The Daily Galaxy, Max Goldberg via NASA
Image credits: Chandra: NASA/CXC/NRL/S. Giacintucci, et al., XMM-Newton: ESA/XMM-Newton; Radio: NCRA/TIFR/GMRT; Infrared: 2MASS/UMass/IPAC-Caltech/NASA/NSF