A giant observatory buried in Antarctic ice helps scientists catch ghostly neutrinos and trace their source back The center of a galaxy about 47 million light-years from Earth offers a new way to study the supermassive black holes lurking within.
Neutrinos are heading toward Earth from the center of a spiral galaxy called Messier 77 (M77), according to a new study published Nov. 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 orbiting it,” said Ignacio Taboada, a spokesman for the international study and a professor of 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 spooky property gives scientists an unprecedented way to probe what’s happening around a black hole, including how it accelerates nearby superheated charged gas and matter.
“Neutrinos are another way of looking at the universe. Every time you look at the universe in a new way, you learn something you couldn’t learn the old way,” Taboada said.
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 studying them to better understand the interactions that create and accelerate these neutrinos within M77, as well as the behavior and properties of the black hole itself, Niedhausen said.
They also plan to tease out 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 detection 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 Earth, they occasionally 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, largely funded 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 Earth’s atmosphere, but the observatory also detects about hundreds of neutrinos from beyond the solar system each year — called “astrophysical neutrinos.”
Because neutrinos can penetrate matter without being affected, they travel in exactly 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 International IceCube 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 Information Sources.”
Taboada said he thinks 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 future detections could not only help unravel more details about M77’s supermassive black hole, but also help answer “astronomical questions”. the oldest question in the world”.
Scientists have known for more than a century the existence of cosmic rays—streams of high-energy protons and atomic nuclei that travel near the speed of light and produce electromagnetic radiation and showers of subatomic particles as they strike Earth’s atmosphere. But where do these rays come from? What mechanism accelerates and sends it in the direction of 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 interacting with matter and radiation around high-energy objects such as supermassive black holes, so, Halzen and Taboada say, tracing ghost particles back to their source could help resolve the origin of cosmic rays question. ◇
Responsible editor: Li Qiong#