These neutrinos have significantly more energy than any other type of neutrino we’ve seen on Earth, and far more than any of our experiments could hope to produce. They’re particularly significant since they point to dramatic cosmic occurrences. The precise source (or sources) is unknown, but it could include black holes, pulsars, supernova remnants, intense explosions known as gamma-ray bursts, and active galactic nuclei (the bright, compact region at the center of a galaxy). It could even be a completely new form of source that no one has ever seen before.
Cosmic neutrinos recorded by the IceCube experiment, a neutrino telescope composed of a cubic kilometer of Antarctic ice, were the most energetic neutrinos yet seen. Neutrinos with petaelectronvolts of energy, or one thousand trillion electronvolts, were observed by researchers. This is a massive quantity of energy in the particle world. A typical atmospheric neutrino (produced in our own atmosphere by a cosmic ray interaction) has roughly 1 to 10 trillion electronvolts. Even the world’s most powerful particle accelerator, the Large Hadron Collider, smashes particles together at only roughly 13 trillion electronvolts.
For the first time in 2018, IceCube was able to track a high-energy cosmic neutrino back to its source. A blazar, an active galaxy fueled by a supermassive black hole, was the culprit. This launched neutrinos into the age of multi-messenger astronomy, which studies cosmic processes using signals from various types of messengers (such as neutrinos, cosmic rays, gravitational waves, and electromagnetic radiation, or light).