For the first time in history, a team of astronomers has found the origin of a high-energy cosmic neutrino from outside our galaxy. The so-called ‘ghost particles’ detected in Antarctica on September 22, 2017, reveal that it traveled 4,000 million light years to reach us and that this particle came from a blazar , a spiral galaxy with a massive black hole in its rapidly rotating center: an extremely energetic object. So, apparently, apart from neutrinos, gamma rays are partially produced by high-energy protons in jets from supermassive black holes like this blazar.
It is a surprising discovery , which not only confirms blazars as a source of high-energy neutrinos, but also establishes a new field of study: multi-messenger neutrino astrophysics : the use of different types of detectors put together to study the same. phenomenon. This same technique was used in the incredible research that confirmed and photographed colliding neutron stars.
Neutrinos from outside the galaxy
High-energy extragalactic neutrinos have been an enigmatic puzzle since their first detection in 2012, identified with the specialized IceCube neutrino detector at the South Pole, taking advantage of Antarctic ice. Subatomic particles are rare, but they are not much rarer than neutrinos. Their mass is almost zero, they travel almost at the speed of light, and they don’t really interact with normal matter; for them, the universe would be almost incorporeal. Hence the name ‘ghost particle’.
However, that doesn’t mean they can’t interact with matter, and this is where the IceCube Observatory in Antarctica comes in, because from time to time, a neutrino can interact with ice and create a flash of light.
Scientists detected neutrinos from a 1987 supernova in the Milky Way’s galactic halo (sn1987a) with energy up to 36 megaelectronvolts. The 2012 neutrinos also far exceeded any close comparison : the neutrino’s energy was 300 teraelectronvolts, more than 100 million times more energetic or about 20 times more than the LHC, the world’s most powerful particle accelerator.
Considering that for neutrinos, the rest of the universe doesn’t really exist, they always travel in a straight line. And that’s how experts found out where this little subatomic particle came from.
The origin, a blazar 4 billion light-years away called TXS 0506 + 056, right next to Orion , a finding that illustrates that the associated high-energy cosmic rays consisting mainly of protons and atomic nuclei also come from the same place. .
There are several thousand of these known highly energetic objects in the sky; but they had been quite low on the list as possible sources of high-energy neutrinos.
“It’s interesting to see how there was a general consensus in the astrophysics community that blazars were probably not cosmic ray sources, and here we are, ” said University of Wisconsin-Madison physicist Francis Halzen and lead scientist at the IceCube Neutrino Observatory.
The finding was supported by observations from two gamma-ray telescopes: NASA’s orbiting Fermi Gamma-ray Space Telescope and the Cherenkov Telescope (MAGIC) in the Canary Islands. They both detected a flash of high-energy gamma ray activity coming from TXS 0506 + 056.
“All the pieces fit together,” concluded UW-Madison physicist Albrecht Karle and co-author of the Science paper. “The neutrino flare in our archival data became independent confirmation. Together with observations from other observatories, it is compelling evidence that this blazar is a source of extremely energetic neutrinos and therefore high-energy cosmic rays. Energy”.
Referencia: Multimessenger observations of a flaring blazar coincident with high-energy neutrino IceCube-170922A. Science 13 Jul 2018: Vol. 361, Issue 6398, eaat1378 DOI: 10.1126/science.aat1378 // Neutrino emission from the direction of the blazar TXS 0506+056 prior to the IceCube-170922A alert Science 13 Jul 2018:Vol. 361, Issue 6398, pp. 147-151 DOI: 10.1126/science.aat2890
Crédito imagen: DESY, Science Communication Lab
