In this artistic rendering, a blazar is accelerating protons that produce pions, which produce neutrinos and gamma rays. Neutrinos are always the result of a hadronic reaction such as the one displayed here. Gamma rays can be produced in both hadronic and electromagnetic interactions. (ICECUBE/NASA)

A Cosmic First: Ultra-High Energy Neutrinos Found, From Blazing Galaxies Across The Universe

In 1987, we detected neutrinos from another galaxy in a supernova. After a 30 year wait, we’ve found something even better.

Ethan Siegel
8 min readJul 19, 2018

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One of the great mysteries in science is determining not only what’s out there, but what creates the signals we detect here on Earth. For over a century, we’ve known that zipping through the Universe are cosmic rays: high energy particles originating from far beyond our galaxy. While some sources for these particles have been identified, the overwhelming majority of them, including the ones that are most energetic, remain a mystery.

As of today, all of that has changed. The IceCube collaboration, on September 22, 2017, detected an ultra-high-energy neutrino that arrived at the South Pole, and was able to identify its source. When a series of gamma-ray telescopes looked at that same position, they not only saw a signal, they identified a blazar, which happened to be flaring at that very moment. At last, humanity has discovered at least one source that creates these ultra-energetic cosmic particles.

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Ethan Siegel
Starts With A Bang!

The Universe is: Expanding, cooling, and dark. It starts with a bang! #Cosmology Science writer, astrophysicist, science communicator & NASA columnist.