For the first time ever, scientists have mysteriously received delayed signals from two supermassive black holes snacking on stars in their vicinity.
In the first case, a black hole weighing as much as 30 million suns in a galaxy about 750 million light-years away swallowed a star that passed too close to the edge. Light from the event was spotted in April 2019, but a telescope came in six months later Antarctica caught an extremely high-energy and ghostly particle – one neutrino – which was apparently quenched during the party.
A second incident involved a supermassive black hole about 1 million times the mass of the Sun in a galaxy about 700 million light years away. Observatories spied it on a star during a luncheon in August 2015, then went silent for a sudden burst of Radio waves appeared in February 2016 and then again, almost four years later, in July 2019.
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Both events involve what is known as a tidal disturbance (TDE), in which a supermassive black hole shreds a star to pieces using its massive gravity – essentially an extreme version of how the moon’s gravitational pull tides on the tides. SoilSuch cosmic events are still not well understood, and these two new findings should greatly help astronomers unlock their inner workings.
“Anytime we detect a new TDE, there can always be something exciting and unexpected associated with it,” Jane Dai, who studies high-energy astrophysics at the University of Hong Kong, told Live Science. “So there’s a lot of new physics that can be done,” added Dai, who was not involved in either of the findings.
Researchers classify tidal disturbances as “transient” phenomena, as they typically flare up and then fade over the course of a few days. What exactly creates the light in such cases is still not entirely clear, 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 tears its stellar meal, the star is “spagetted” into a long thin stream. This deluge of material wraps around the black hole and is believed to produce a beam of energy as it orbits like water flowing down a drain, although other models predict that part of the former star could explode outward and interact with surrounding gas and dust, causing the torch, Horesh said.
Given the extreme environment around the black hole, particles can be greatly accelerated in processes similar to nuclear destroyers such as the Large Hadron Collider in Geneva, Switzerland. Neutrinos are tiny dots that are about 500,000 times lighter than an electron and because they are neutral (have no charge), they don’t interact with many as they fly through the cosmos.
This allowed a single neutrino to travel to Earth from the first TDE and eventually appear in a one-square-mile instrument known as the IceCube Neutrino Observatory buried in the Antarctic ice. Researchers named the detection IC191001A and calculated that it had nearly 1 trillion electron volts of energy, making it one of the most powerful neutrinos IceCube has ever seen, according to one of the new articles.s, published in the magazine Feb. 22 Nature Astronomy
Although physicists have predicted neutrinos to be produced by tidal disturbances, astronomers have never fed a neutrino back to a particular TDE, making this a spectacular first. Why it arrived six months after the event itself: “I have no idea,” Horesh said.
A similar mystery surrounds the second study he conducted, inside too Nature astronomy In that case, optical light – the kind our eyes see – was seen flickering from a snacking black hole and then fading, as is common with these phenomena.
Horesh and his co-authors decided to conduct follow-up research with the Karl Jansky Very Large Array (VLA) telescope in New Mexico, which detects radio waves. They saw nothing coming out of the black hole for months and then, suddenly, six months after the first event, a bright radio flame. Stranger still, VLA data collected nearly four years later showed another curious burst of radio energy.
“Someone could make up a story about why we saw something six months later,” Horesh said. “There is nothing that explains why it should flare up, decay and then flare up again. It’s really interesting. ‘
He points to the need for new models that can explain these delayed signals. His team speculates that some of the energy beam comes out at an odd angle, creating a flashing pattern that is sometimes seen and sometimes not when the accretion disk spins. Another possibility is that the stellar remnants drive shock waves that move slowly through the material around the black hole and later produce energetic emissions, although no one really knows.
But as these incidents now seem to be taking longer than initially suspected, Horesh is looking forward to detecting more tidal disturbances that could provide insight into their nature.
Dai, too, is excited about the prospect of opening ways to study the mysteries of TDEs. “These events are ideal laboratories to learn about black holes,” she said, giving researchers important clues about how material collects around them and produces jets and flares.
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 emerging space tools from Europe and China should contribute to this bounty.
“The future for the field looks very bright,” she said.
Originally published on Live Science.