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Scientists Find Previous Outbursts of Neutrinos in the Galaxy

15 Juillet 2018

To begin unravelling a century-long mystery in cosmology, astronomers first had to catch a ghost.

Neutrinos are called ghost particles because they are incredibly small and hard to detect.

In a paper published this week in the journal Science, scientists have, for the first time, provided evidence for a known blazar, designated TXS 0506+056, as a source of high-energy neutrinos.

Neutrinos, sometimes called ghost particles, are electrically neutral and almost massless, allowing them to travel through the cosmos for billions of light-years, passing unhindered through galaxies, stars, planets and dust. Not only do they permeate space all around us, but every second tens of thousands of neutrinos pass through your body.

"We had this neutrino alert in September 2017", says Olga Botner, a particle physicist at Uppsala University in Sweden and a member of the National Science Foundation-funded IceCube scientific team. They present their own challenges, though.

An worldwide team of scientists has found the first evidence of a source of high-energy cosmic neutrinos - ghostly subatomic particles that can travel unhindered for billions of light-years from the most extreme environments in the universe to Earth. Fittingly, it's called IceCube. This will allow us to study neutrinos with lower energies than we can now, and also to more accurately measure the optical properties of the Antarctic ice. The impact exploded the nucleus, blasting out a cone of rippling radiation, mostly in the form of light waves. Within a minute, they had relayed a message to telescopes around and orbiting the globe to train their sights on a small patch of sky within the Orion constellation. Presumably it is some kind of supermassive black hole rumbling in the heart of that distant galaxy.

A key feature of blazars is twin jets of light and elementary particles that shoot from the poles of the swirling whirlwind of material surrounding the black hole.

Experts say it is nearly impossible to trace the path of these rays to their origin, since most are charged particles that do not travel in a straight line.

Later research showed them to be made up of protons, electrons or atomic nuclei accelerated to speeds approaching that of light. A parallel global and intergalactic project, largely based in Western Australia, to set up the biggest, most powerful radio telescope ever built, called the Square Kilometre Array, involves more than a million antennas. Yet these qualities make them invaluable for conveying information across time and space, scientists say.

But how they are created and where they come from has been an enduring mystery.

NASA's Fermi Gamma-ray Space Telescope and the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) Telescope in the Canary Islands, both of them recognized the same source of unpredictable particle which is very powerful: a blaze of cosmic rays with high energy level, shooting into space from a faraway enormous black hole, this powerful phenomenon is also called as blazer. This is why the teams rely on neutrinos to sniff out the origin of the other particles.

"This result really highlights the importance of taking a multimessenger approach to these searches", said Erik Blaufuss, a research scientist in the UMD Department of Physics who led the effort over the past several years to create and deploy IceCube's high-energy event alert system. NPR puts it similarly: "It's an achievement that opens a whole new way of looking at the universe". We would also like to see which subtypes of AGN produce neutrinos.

Scientists Find Previous Outbursts of Neutrinos in the Galaxy