Scientists may have found the cosmic birthplace of an ultra-high energy neutrino. They point the finger at a blazar — a brilliantly luminous galaxy that shoots a jet of radiation in the direction of Earth — 9 billion light years away.
If the link between the blazar and neutrino is real, scientists would be closer to long-sought answers about where such power-packing particles come from. Violent astronomical accelerators boost some neutrinos to high energies, but scientists have never been able to convincingly identify their sources.
Neutrinos are aloof elementary particles that rarely interact with other matter — they can sail straight through the Earth, and trillions of them zip through your body every second without a trace. On December 4, 2012, the neutrino in question (which scientists have affectionately nicknamed Big Bird) slammed into the Antarctic ice with an energy of around 2 million billion electron volts. The neutrino observatory IceCube glimpsed the aftermath of the collision and measured its energy with sensitive detectors embedded deep in the ice (SN Online: 04/07/14), leaving scientists hustling to pinpoint its source.
The blazar flared up at just the right time and place to be a prime suspect, researchers report in a paper accepted for publication in a peer-reviewed journal. The result, now available online at arXiv.org, strengthens the case that blazars are the source of such high-energy neutrinos, but it is no smoking gun.
After the neutrino was detected, a team of astrophysicists scoured the heavens for energetic galaxies with TANAMI, short for Tracking Active Galactic Nuclei with Austral Milliarcsecond Interferometry, a network of telescopes peering into space at a variety of wavelengths. That team reported one likely candidate blazar.
But the candidate is not a surefire match…