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For the first time ever, scientists have received mysteriously delayed signals from two supermassive black holes nibbling at nearby stars.
In the first case, a black hole weighing up to 30 million suns located in a galaxy about 750 million light years away engulfed a star that passed too close to its edge. Light from the event was spotted in April 2019, but six months later a telescope Antarctic captured a very high-energy ghostly particle – a neutrino – who apparently burped during the party.
A second incident involved a supermassive black hole with about 1 million times the mass of the sun in a galaxy about 700 million light years away. Observatories saw him having lunch on a star in August 2015, then falling silent before a sudden explosion of radio waves appeared in February 2016 and then again, almost four years later, in July 2019.
Related: 10 huge black hole discoveries from 2020
Both events involve what’s called a Tidal Disturbance Event (TDE), where a supermassive black hole tears a star to pieces using its colossal gravitational pull – essentially an extreme version of how the gravitational pull of the moon raises the tides on the Earth. Such cosmic events are still not well understood, and these two new findings should go a long way to helping astronomers unlock their inner workings.
“Anytime we detect a new TDE, there can always be something exciting and unexpected associated with it,” said Jane Dai, who studies high energy astrophysics at the University of Hong Kong. , at Live Science. “So there is a lot of physical news that can be made,” added Dai, who was not involved in either of the two discoveries.
Researchers classify tidal disturbance events as “transient” phenomena because they typically erupt over the course of a few days and then subside again. It is still not entirely clear what exactly creates the light in such cases, Assaf Horesh, an astronomer at the Hebrew University of Jerusalem in Israel and co-author of two articles on the new events, told Live Science.
As the supermassive black hole rips through its stellar meal, the star becomes “spaghetti” in a long, thin stream. This torrent of matter wraps around the black hole and is believed to produce a jet of energy as it spins like water flowing down a drain, although other models predict that some of the ancient stars could explode outward and interact with surrounding gas and dust, generating the flare, Horesh said.
Given the extreme environment surrounding the black hole, particles can become dramatically accelerated in processes similar to atom breakers like the Large Hadron Collider in Geneva, Switzerland. Neutrinos are tiny dots about 500,000 times lighter than an electron and, being neutral (not having a charge), they don’t interact with much as they fly through the cosmos.
This allowed a single neutrino to travel outward from the first TDE and head towards Earth, eventually appearing in a square kilometer-sized instrument known as the IceCube Neutrino Observatory, buried in the Antarctic ice. The researchers labeled the detection IC191001A and calculated that it had nearly 1 quadrillion electron volts of energy, making it one of the most powerful neutrinos IceCube has ever seen, according to one of the newcomers. articles.s, which was published on February 22 in the newspaper Nature astronomy.
While physicists have predicted that neutrinos are produced during tidal disturbance events, astronomers have never linked a neutrino to a particular TDE, making it a spectacular first. As to why it happened six months after the event itself, “I have no idea,” Horesh said.
A similar mystery surrounds the second study he conducted, also Nature astronomy . In this case, optical light – the one our eyes see – was seen to escape from a nibbling black hole and then fade away, as usual for these phenomena.
Horesh and his co-authors decided to conduct follow-up studies using the Karl Jansky Very Large Array (VLA) telescope in New Mexico, which detects radio waves. They didn’t see anything coming from the black hole for months, then suddenly, six months after the initial event, a radio light flare. Even stranger, VLA data collected almost four years later showed another curious explosion of radio energy.
“Someone can make up a story to explain why we saw something six months later,” Horesh said. “There’s nothing to explain why it should catch fire, decompose and then catch fire again. It’s really interesting.”
It highlights the need for new models that can explain these delayed signals. His team speculates that part of the energy jet comes out at an odd angle, producing a flared pattern that is sometimes seen and sometimes not as the accretion disc spins. Another possibility is that the stellar remnants cause shock waves that move slowly through the material surrounding the black hole, which produces energetic emissions at later times, although no one really knows.
But given that these incidents now appear to be going on for longer than initially thought, Horesh is eager to be able to detect more tidal disturbance events that could provide insight into their nature.
Dai, too, is excited about the prospect of opening up avenues for studying the mysteries of TDE. “These events are ideal laboratories for learning more about black holes,” she said, giving researchers important clues as to how materials grow around them and produce jets and rockets. illuminating.
The Vera C. Rubin Observatory in Chile, which is expected to start collecting data this year, could theoretically see hundreds of new TDEs, she added; and other upcoming space instruments from Europe and China are expected to add to this premium.
“The future of the field is very bright,” she said.
Originally posted on Live Science.
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