[Epoch Times October 17, 2021]A new study shows that when a black hole swallows a star, it may not generate enough energy to emit high-energy neutrinos. Scientists are uncertain about the previous conclusion that this extremely drastic celestial change must be the source of high-energy neutrinos.
Neutrinos are one of the smallest particles known in physics. It is a subatomic particle, although it has mass, but the mass is extremely small. And it rarely interacts with other particles. Therefore, this ghostly particle is considered to be one of the main components of dark matter.
The IceCube Neutrino Observatory in Antarctica can detect neutrinos from the universe. In October 2019, a high-energy neutrino hit the IceCube Observatory. This rare high-energy neutrino immediately aroused the interest of astronomers: What celestial body can produce such a powerful neutrino?
The IceCube team traced the neutrino back to a supermassive black hole that had just swallowed a star. This astronomical event numbered AT2019dsg is a tidal destruction event, that is, an astronomical event in which stars are torn apart and destroyed under the action of the gravitational tide of a black hole.
This tidal destruction event came from the same area of the sky as the neutrino signal, but it happened a few months ago. Many astronomers believe that this extremely drastic celestial change must be the source of high-energy neutrinos.
But a new study questions this claim.
The research team of Northwestern University and the Harvard-Smithsonian Center for Astrophysics has provided a large number of new radio observations and data on AT2019dsg, enabling the team to calculate the energy emitted by the event.
The results of the study show that the energy produced by AT2019dsg is not enough to produce the observed high-energy neutrinos. In fact, the things spewed out by this tidal destruction event are very “ordinary,” the team concluded.
Although this may seem counterintuitive, black holes do not always swallow everything within reach.
“Black holes are not like vacuum cleaners.” Yvette Cendes, a postdoctoral fellow at the Harvard-Smithsonian Center for Astrophysics who led the research, said in a statement.
Sanders explained that when a star is too close to a black hole, the strong gravitational force of the black hole will tear the star into a spaghetti shape. Eventually, the slender stellar debris hovered around the black hole and heated up, creating a flash of light in the sky that astronomers could spot millions of light years away.
“However, when there is too much matter, the black hole cannot eat it all at once,” the research collaborator and Northwestern University postdoc Kate Alexander said in the statement. “During this process, some gas will be spit out, just like when a baby eats, some food will eventually fall on the floor or wall.”
These remnants are thrown back into space in the form of wind or jets. If the jet is strong enough, it can indeed produce high-energy neutrinos in theory.
Using the Very Large Array in New Mexico, USA and the Atacama Large Radio Telescope Array (ALMA) in Chile, the research team was able to observe the distance from us more than 500 days after the black hole began to swallow the star About 750 million light-years of AT2019dsg.
Excellent radio observations make AT2019dsg the most well-studied TDE so far, and it shows that the radio brightness reaches its peak about 200 days after the beginning of the event.
The data shows that the total amount of energy emitted is equivalent to the energy radiated by the sun over the course of 30 million years. Although this sounds impressive, the high-energy neutrinos discovered in October 2019 require a source 1,000 times higher in energy to produce.
Alexander explained in the statement: “We didn’t see the bright jets of matter needed for this, but the weaker radio current.”
“What we see is an outflow like a breeze, not a powerful jet like a high-pressure water gun.” Sundes added, “If this neutrino comes from AT2019dsg in some way, then it raises a question: why We have not found neutrinos associated with supernovae at this distance or closer? They are more common and have the same energy velocity.”
The team concluded that neutrinos are unlikely to come from this particular tidal destruction event. If this is the case, astronomers are far from understanding the dramatic changes in celestial bodies such as tidal destruction events and the true causes of high-energy neutrino signals. Perhaps this means that there are more violent celestial body disintegration and renewal processes in the distant universe that are still unknown.
“We may check this question again.” Sundance said, he thinks there is still a lot to learn. “This particular black hole is still eating.”
The paper for this new study was published in the Astrophysical Journal.
Editor in charge: Lin Yan#
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