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Brightest space explosion reveals possible evidence of dark matter

Brightest space explosion reveals possible evidence of dark matter
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ONm Sunday, October 9th, Judith Racusin was 35,000 feet in the air, en route to a high-energy astrophysics conference, when the largest cosmic explosion in history took place. “I landed, looked at my phone, and had dozens of messages,” said Racusin, an astrophysicist at NASA’s Goddard Space Flight Center in Maryland. “It was really extraordinary.”

The explosion was a long gamma-ray burst, a cosmic event in which a massive dying star releases powerful beams of energy as it collapses into a black hole or neutron star. This particular flare was so bright that it saturated the Fermi Gamma-ray Space Telescope, an orbiting NASA telescope designed in part to observe such events. “There were so many photons per second they couldn’t keep up,” they said Andrew Levan, astrophysicist at Radboud University in the Netherlands. The eruption even appears to have caused Earth’s ionosphere, the upper layer of Earth’s atmosphere swell in size for several hours. “The fact that you can change the Earth’s ionosphere from an object halfway across the universe is pretty incredible,” he said Doug Welchan astronomer at McMaster University in Canada.

Astronomers cheekily dubbed it the BOOT – “the brightest ever” – and started squeezing it to get information about gamma-ray bursts and the cosmos in general. “Even 10 years from now, there will be new insights from this dataset,” he said Eric Burns, an astrophysicist at Louisiana State University. “It’s still not entirely clear to me that that actually happened.”

The first analysis suggests that there are two reasons why the BOOT was so bright. First, it happened about 2.4 billion light-years from Earth — pretty close for gamma-ray bursts (although far outside our galaxy). It is also likely that the BOAT’s powerful beam was aimed at us. The combination of these two factors makes this an event that only occurs once every few hundred years.

Perhaps the most momentous observation happened in China. There, in Sichuan province, the Large High Altitude Air Shower Observatory (LHAASO) tracks high-energy particles from space. In the history of gamma-ray burst astronomy, researchers have only seen a few hundred high-energy photons emanating from these objects. LHAASO 5,000 views from this one event. “The gamma-ray burst basically started right above them in the sky,” he said Sylvia ZhuAstrophysicist at the German Electron Synchrotron (DESY) in Hamburg.

Among those detections was a suspected high-energy photon at 18 teraelectronvolts (TeV) — four times higher than anything previously observed from a gamma-ray burst and more energetic than the highest energies achievable with the Large Hadron Collider. Such a high-energy photon should have been lost en route to Earth, absorbed by interactions with the universe’s background light.

So how did it get here? she probability is that after the gamma-ray burst, a high-energy photon was converted into an axion-like particle. axions are hypothetical light particles that could explain dark matter; Axion-like particles are considered slightly heavier. High energy photons could be transformed into such particles by strong magnetic fields, such as those created around an imploding star. The axion-like particle would then move unhindered through the vast expanse of space. Upon its arrival in our galaxy, magnetic fields would convert it back into a photon, which would then find its way to Earth.

In the week after the first discovery, several teams of astrophysicists proposed this mechanism in articles uploaded to the scholarly preprint site arxiv.org. “It would be a very incredible discovery,” said Giorgio Galanti, an astrophysicist at the National Institute for Astrophysics (INAF) in Italy, who was one of the co-authors first of these papers.

Still other researchers wonder if the discovery of LHAASO could be a case of mistaken identity. Perhaps the high-energy photon came from somewhere else, and its exact arrival time was just a coincidence. “I’m very skeptical,” he said Milena Crnogorcevic, an astrophysicist at the University of Maryland. “I’m currently leaning towards it being a background event.” (To complicate matters further, a Russian observatory reported a hit by an even more energetic 251 TeV photon originating from the burst. But “no verdict has been made on that yet,” said Racusin, deputy project scientist at the Fermi telescope. “I’m a bit skeptical.”)

So far, the LHAASO team has not published detailed results of their observations. Burns, who is coordinating a global collaboration to explore the BOAT, hopes that’s the case. “I’m very excited to see what they have,” he said. But he understands why a degree of caution may be warranted. “If I was sitting on data that had even a ten percent chance of being conclusive evidence of dark matter, I would be extraordinarily cautious right now,” Burns said. If the photon can be linked to the BOOT, “it would very likely be evidence of new physics and possibly dark matter,” Crnogorčević said. The LHAASO team did not respond to a request for comment.

Even without LHAASO’s data, the sheer amount of light seen from the event could allow scientists to answer some of the biggest questions about gamma-ray bursts, including important mysteries about the jet itself. “How is the jet launched? What is going on inside the jet as it expands into space?” said Tyler Parsotan, an astrophysicist at Goddard. “Those are really big questions.”

Other astrophysicists hope to use the BOOT to figure out why only some stars produce gamma-ray bursts when they go supernova. “That’s one of the big mysteries,” he said Yvette Cendes, an astronomer at the Harvard-Smithsonian Center for Astrophysics. “It must be a very massive star. A galaxy like ours produces a gamma-ray burst every million years. Why is such a rare population producing gamma-ray bursts?

Whether gamma-ray bursts at the core of the collapsed star will lead to a black hole or a neutron star is also an open question. Preliminary analysis of the BOAT suggests that in this case the former happened. “There’s so much energy in the jet that it’s basically a black hole,” Burns said.

What is certain is that this is a cosmic event that will not be eclipsed for many, many lifetimes. “We’ll all be long dead before we get a chance to do that again,” Burns said.

Lead image: The rings around the outburst, seen here in colorized data from NASA’s Swift Observatory, formed as X-rays were scattered from buried dust in our Milky Way. Photo credit: NASA Swift Observatory; Editing: Jon Miller.

This article was originally published on the quantum abstractions to blog.



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