Rare sighting of a luminous jet from a star-eating supermassive black hole
Over 8 billion years ago, a star was torn apart as it got too close to a supermassive black hole. Jets of gas directed towards Earth recently made the fate of the star visible to a telescope looking for new sources of light in the night sky. The observation has led to two independent publications including researchers at Stockholm University in Nature and Nature Astronomy.
“We had to exclude all other possible explanations to understand what we were looking at. It looked neither like a supernova nor like more exotic phenomena such as gamma-ray bursts or kilonovae, so we concluded that it had to be a black hole tearing a star apart in an unusual way,” says Jesper Sollerman, professor at the Department of Astronomy and co-author of the article in Nature.
8 billion years away
On February 11 2022, a team of astronomers using the Zwicky Transient Facility (ZTF) in California discovered an unusual optical flare. ZTF finds dozens of exploding stars each night, but the new object changed in brightness too fast to be a regular supernova. The discovery caused several groups of astronomers to point all kinds of telescopes towards the new transient, dubbed AT2022cmc. A spectrum revealed that it was in fact very distant: the light from AT2022cmc had been traveling towards Earth for the past 8 billion years.
Star being torn apart
Now two teams of astronomers, both of which include researchers at Stockholm University, have simultaneously published their independent analyses of the distant flash. Both teams conclude that the flash is the result of a star being torn apart by a spinning supermassive black hole, launching jets pointing in the direction of the Earth.
The discovery team from ZTF, led by Andreoni and Coughlin, have published their result in Nature. They estimate that relativistic jets are launched in only 1% of such destructive events, making AT2022cmc an extremely rare occurrence.
“It has been more than 10 years since a similar event was found previously, and this is the first time it has been discovered in the optical regime. The fact that it was observed in the optical regime enabled the discovery at a very large distance. It may be the only way to identify and study otherwise dormant supermassive black holes in the early universe,” says Jesper Sollerman.
Almost the speed of light
Another team focused on the very bright X-ray counterpart, and estimated that the jet was launched at more than 95% of the speed of light. Their results appear in Nature Astronomy.
“Future telescopes like the Vera Rubin Observatory will probably find many more of these events now that we know what to look for. The trick is just to single these rare events out from the thousands of new flashes of light that this survey will unveil every night,” says Ana Sagués-Carracedo, PhD-student at the Department of Physics at Stockholm University and part of the ZTF team that discovered AT2022cmc.
This is an artist’s impression of how the material of a star fell towards the black hole at the centre of a distant galaxy, producing jets of matter and radiation. Because the jets are pointing almost towards us, the event, called AT2022cmc, could be discovered from Earth with an optical telescope for the first time. Credit: ESO/M.Kornmesser More information and download options
Nature: The paper, “A very luminous jet from the disruption of a star by a massive black hole,” by Andreoni, Coughlin et al. was published in Nature on November 30, 2022. The paper in Nature includes Ana Sagués-Carracedo and Steve Schulze from the Department of Physics at Stockholm University as well as Jesper Sollerman, Mattia Bulla and Erik Kool from the Department of Astronomy, all affiliated with the Oskar Klein Centre.
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Nature Astronomy: The paper "The birth of a relativistic jet following the disruption of a Star by a cosmological black hole" by Pasham et al. was published in Nature Astronomy on the same date. Co-authors from Stockholm University on the paper in Nature Astronomy includes Oskar Klein Centre-affiliated researchers Janet Chen, Sheng Yang, Sean Brennan from the Department of Astronomy and Steve Schulze from the Department of Physics.
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Facts - the research on supernovae, stars and black holes
Research into supernovae, stars and black holes takes place, at the Department of Astronomy at Stockholm University. The supernova group studies the structure, dynamics and element formation in supernovae via models and observations. Much of the research in the area takes place in collaboration with the Physics department at Stockholm University within the framework of the joint Oskar Klein Centre.
Funding and resources
The Swedish participation in ZTF is supported by the Swedish Research Council (Vetenskapsrådet) and by the Knut and Alice Wallenberg Foundation.
The publication in Nature was done using telescope resources from the European Southern Observatory.
Last updated: December 7, 2022
Source: Communications Office