A huge observatory buried in Antarctic ice is helping scientists catch ghost neutrinos and trace their origins The center of a galaxy about 47 million light-years from Earth offers a new way to study supermassive black holes that lurks in it.
Neutrinos are going to Earth from the center of a spiral galaxy called Messier 77 (M77), according to a new study published November 3 in the journal Science. There, a dense region of matter and radiation surrounds a black hole millions of times the mass of the Sun.
The location of M77 is so obscured by the dust and gas surrounding the black hole that it cannot be seen from Earth with an optical telescope,
“We looked at the galaxy from the side and found the black hole hidden behind the matter rotating it,” said Ignacio Taboada, spokesman for the international study and professor physics at Georgia Tech.
Neutrinos – the most abundant and energetic particles in the universe – travel through such gas and dust unaffected, the researchers say, because they interact less with other things, including magnetic fields, matter or gravity . This surprising property gives scientists an unprecedented way to investigate what happens around a black hole, including how it accelerates gas and superheated charged matter nearby.
“Neutrinos are another way of looking at the universe. Every time you look at the universe in a new way, you learn something that you couldn’t learn the old way,” said Taboada.
Neutrinos retain the information they left behind when they were created, including their energy, said Hans Niederhausen, a postdoctoral associate at Michigan State University who worked on the study. The same energy is carried to Earth along with neutrinos.
Now that we know where these neutrinos come from, researchers have begun to study them to better understand the interactions that create and accelerate these neutrinos within M77, as well as their behavior and properties the black hole itself, said Niedhausen.
They also plan to pick up neutrinos from other galaxies in the universe that have active supermassive black holes similar to M77. The galaxy “gives us a very good idea of where to look next,” he added.
The neutrino-detecting telescope used in the study, also known as the IceCube Neutrino Observatory, is buried in a billion-ton ice sheet around the Amundsen-Scott South Pole Station in the United States. As neutrinos pass through the Earth, they sometimes collide with atoms in the ice. The observatory’s more than 5,000 basketball-sized sensors can detect the byproducts of these rare collisions and send that data to computers on the surface.
The $279 million observatory, funded primarily by the National Science Foundation and completed in 2011, can detect about 100,000 neutrinos a year.
Almost all of these neutrinos detected by the observatory are produced in the Earth’s atmosphere, but the observatory also detects around hundreds of neutrinos from beyond the solar system each year – known as “astrophysical neutrinos.”
Because neutrinos can penetrate matter unaffected, they travel in straight lines from where they were created. So by mapping the direction in which astrophysical neutrinos travel through the ice, researchers can reconstruct their path through the universe back to their source.
Nearly 400 scientists from more than 50 institutions formed the IceCube International Collaboration to analyze data collected by the observatory between 2011 and 2020 to identify 79 neutrinos from the M77 galaxy.
Dr Yoshi Uchida, professor of physics at Imperial College London, who was not involved in the study, said: “The one-day observation, after running for 10 years, turned the neutrino observation into another Source of Information.”
Taboada said he believes research will continue to get more neutrinos from the galaxy. Francis Halzen, a physicist at the University of Wisconsin-Madison and the project’s principal investigator, said that future discoveries could not only help unravel more details about the supermassive black hole M77, but also help answer the “astronomical questions” of the oldest question in the world ” .
Scientists have known for over a century about the existence of cosmic rays – streams of high-energy protons and atomic nuclei that travel at close to the speed of light and produce electromagnetic radiation and showers of subatomic particles as they hit the Earth’s atmosphere. But where do these rays come from? What mechanism accelerates and sends it towards Earth remains a mystery.
“Something in the universe kicked them and made them run fast,” Niederhausen said of cosmic rays.
Neutrinos are by-products of cosmic rays that interact with matter and radiation around high-energy objects such as supermassive black holes, so, according to Halzen and Taboada, tracing ghost particles back to their source could help solve the question of the origin of rays cosmic. ◇
Responsible editor: Li Qiong#