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The ghost particles that chopped up stars reveal cosmic particle accelerators

The ghost particles that chopped up stars reveal cosmic particle accelerators

Smoking gun: After the supermassive black hole tears apart the star, about half of the stellar fragments are thrown back into space, while the rest form a luminous accretion disk around the black hole. The system emits bright light at many wavelengths and is thought to produce a vibrant jet-like outflow perpendicular to the accretion disk. The central powerful engine near the accretion disk ejected these fast subatomic particles.Image source: DESY, Science Communication Laboratory

Scientists tracked a ghostly particle to a shredded star and discovered a huge cosmic particle accelerator. After the doomed star is too close to the supermassive black hole in the center of its parent galaxy and torn apart by the black hole’s huge gravitational force, subatomic particles called neutrinos are thrown towards the earth.This is the first particle that can be traced back to this “tidal destruction event” (TDE) and provides evidence that these little-known cosmic disasters can be powerful natural particle accelerators, as described by DESY scientist Robert Stein ( The research team led by Robert Stein reported in the journal Natural astronomy. These observations also prove the power of exploring the universe by combining different “messengers” (such as photons (particles of light) and neutrinos), also known as multi-messenger astronomy.

The neutrino started its journey about 700 million years ago, around the time when the first animals appeared on Earth. That is the travel time required for particles to reach Earth from the distant, unnamed galaxy (catalog number 2MASX J20570298 + 1412165) in the constellation of Delphi (Dolphin). Scientists estimate that huge black holes have as many as 30 million suns. Stein said: “The closer you get to something, the stronger the gravity. This means that the gravitational force of the black hole pulls the near side of the star stronger than the far side force of the star, thereby producing a stretching effect.” Stein explained. “This difference is called tidal force. As the star gets closer, this stretching becomes more extreme. Eventually it tears the star apart, and then we call it a tidal destruction event. This is what caused the ocean to occur on Earth. The same process as the tides. But fortunately for us, the pull of the moon is not enough to crush the earth.”

About half of the star debris was thrown into space, while the other half fell on the vortex disk surrounding the black hole. The accretion tray is somewhat similar to the water vortex above the bathtub drain. Before falling into oblivion, the material from the accretion disk gets hotter and shiny. The glow was first detected at the Zwicky Transient Facility (ZTF) in Palomar Mountain, California on April 9, 2019.

Half a year later, on October 1, 2019, the IceCube neutrino detector in Antarctica discovered an extremely high-energy neutrino from the direction of the tidal destruction event. DESY co-author Anna Franckowiak said: “It plunged into the Antarctic ice with an amazing energy of 100 trillion teravolts, and is now a professor at Bochum University. “By comparison, this is at least the most powerful particle in the world. Accelerator-Ten times the maximum particle energy that can be achieved by the Large Hadron Collider at CERN near Geneva. “

When the star approaches the black hole, the huge tidal force stretches it until it is finally shredded. Half of the stellar debris is thrown back into space, while the rest forms a rotating accretion disk from which two strong material outflows shoot up and down. The system acts as a powerful natural particle accelerator.Image source: DESY, Science Communication Laboratory

Extremely lightweight

Very lightweight neutrinos hardly interact with any object. They can not only pass through walls, but also through entire planets or stars without being noticed, so they are often called phantom particles. Therefore, even capturing only one type of high-energy neutrino is already a remarkable discovery. Analysis shows that the coincidence of this particular neutrino with TDE is only a fraction of 500. This detection prompted people to use many instruments on the electromagnetic spectrum (from radio waves to X-rays) to further observe events.

Stein said: “This is the first neutrino related to the tidal destruction event, and it brings us valuable evidence.” “The tidal destruction event is not yet known. The detection of neutrinos shows that it is absorbing There is a powerful central engine near the accumulation disk that ejects fast particles. Moreover, the comprehensive analysis of data from radio, optical and ultraviolet telescopes provides us with more opportunities to prove that TDE can act as a huge particle accelerator.”

The ghost particles that chopped up stars reveal cosmic particle accelerators

Heart of Darkness: View of the accretion disk surrounding the supermassive black hole, with jet-like structures flowing away from the disk. The extreme mass of the black hole will bend space-time, so that the far side of the accretion disk can be seen as the image above and below the black hole.Image source: DESY, Science Communication Laboratory

The best explanation is that the rapid injection of material produced by the central engine that lasts for hundreds of days flows out of the system. This is also needed to explain the observational data, as Walter Winter, the head of the DESY theoretical astrophysics group, and his colleague theorist Cecilia Lunardini (Cecilia Lunardini) from Arizona State University in the same issue Natural astronomy. Winter said: “Neutrinos appeared relatively late, half a year after the start of the stellar feast. Our model naturally explains this timing.”

Cosmic accelerators eject different types of particles, but apart from neutrinos and photons, these particles are charged and are therefore deflected by the interstellar magnetic field during the journey. Only electrically neutral neutrinos can travel straight from the source toward the earth like light, and therefore become valuable messengers of such systems.

Co-author, head of DESY neutrino astronomy and professor Marek Kowalski at Humboldt University in Berlin said: “These comprehensive observations prove the power of multi-messenger astronomy.” “If tidal destruction events are not detected, neutrinos will be just one of many events. 1. Without neutrinos, the observed tidal destruction event would be just one of many events. Only through the combination can we find accelerators and learn something new about internal processes.” High-energy neutrinos and tidal destruction events The connection was discovered through a complex software package called AMPEL, which was developed specifically at DESY to search for correlations between IceCube neutrinos and celestial objects detected by the Zwicky Transient Facility.

tip of the iceberg?

The Zwicky transient facility is designed to capture hundreds of thousands of stars and galaxies at once, and can observe the night sky extremely quickly. At its core is the Samuel Oschin telescope with a diameter of 1.3 m. With its wide field of view, ZTF can scan the entire sky within three nights and find more variable and transient objects than other previous optical measurements. The co-author of the study, Joseph Van Welzen of the Leiden Observatory, said: “Since the beginning of 2018, we have so far detected more than 30 tidal damage events, more than twice the number of known such objects.” When we realized that the second brightest space-time yaw source we observed was the source of high-energy neutrinos recorded by IceCube, we were very excited.”

Francis Halzen, a professor at the University of Wisconsin-Madison and a principal investigator at the University of Francisco, said: “We may only see the tip of the iceberg here. In the future, we expect to find between high-energy neutrinos and their sources. More connections.” IceCube, who was not directly involved in this research. “The new generation of telescopes under construction will provide higher sensitivity to TDE and other potential neutrino sources. The expansion of the planned IceCube neutrino detector is even more necessary, which will increase the number of neutrino detections in the universe. At least ten times.” This TDE marks the second time that high-energy cosmic neutrinos can be traced back to its source. In 2018, a multi-messenger movement proposed an active galaxy, blazar TXS 0506 + 056, which was the first identified source of high-energy neutrinos in history, and IceCube recorded this in 2017.

Researchers have discovered a galactic source of gamma rays that may produce very high-energy cosmic rays

More information:
Accompanying the tidal destruction of high-energy neutrinos, Natural astronomy (2021). DOI: 10.1038 / s41550-020-01295-8, www.nature.com / articles / 10.1038 / s41550-020-01295-8

Courtesy of Deutsches Elektronen-Synchrotron

Citation: Ghost particles in shredded stars reveal the cosmic particle accelerator (2021, February 22), from February 22, 2021 from https://phys.org/news/2021-02-ghost-particle- shredded-star-reveals.html retrieved

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