Today’s evidence of cosmic neutrinos is described as possibly ushering in a new form of astronomy. Before I dive into the discovery of cosmic neutrinos, let’s touch on what exactly neutrinos are.
Neutrinos are nearly massless subatomic particles that travel throughout the universe. Because they aren’t disturbed by other matter, neutrinos point directly back to their origins. These origins are the universe’s most powerful phenomenons including black holes and exploding stars.
“Cosmic neutrinos are the key to yet unexplored parts of our universe and might be able to finally reveal the origins of the highest energy cosmic rays, including the rare ‘Oh-My-God’ particles,” says Botner. “The discovery of astrophysical neutrinos hints at the dawn of a new era in astronomy.”
How neutrinos were discovered in Antarctica
Because neutrinos are never directly observed, researchers used the IceCube Neutrino Observatory to spot the by-products of a neutrino interaction with the Antarctic ice. The specific by-product in question are known as high-energy muons.
Every year, IceCube records thousands of neutrinos. Most of them are created by the interaction of cosmic rays with the Earth’s atmosphere.
So how do researchers filter out the muons created when neutrinos interact with cosmic rays slamming into Earth’s atmosphere with the high-energy neutrinos (muons) they are seeking? By pointing the IceCube Neutrino Observatory at the ground. Yep, you read that right. IceCube observes the Northern Hemisphere sky from the south pole. Earth acts as a giant filter to help weed out all the muons researchers don’t care about.
“Looking for muon neutrinos reaching the detector through the Earth is the way IceCube was supposed to do neutrino astronomy and it has delivered,” says Francis Halzen, the principal investigator of IceCube. “It is not quite CMS and ATLAS, but this is as close to an independent confirmation as one can get with a single instrument.”
In a two-year span beginning in May 2010, IceCube recorded more than 35,000 neutrinos. Of these, only around 20 were observed at energy levels indicating a cosmic source.
One of the 21 highest-energy neutrinos detected. The probable neutrino energy from this event is 466 TeV. Credit: IceCube Collaboration
What kind of energy levels are we talking about? Take CERN’s Large Hadron Collider (LHC). It’s the world’s most powerful accelerator. When cosmic neutrinos are created, they are accelerated to energy levels that are a million times more than what the LHC can produce.
Cosmic neutrinos are such an enticing target because they haven’t changed since leaving their source. By studying them, astronomers and physicists could learn more about the secrets of our universe.
IceCube’s latest observations could, in theory, trace the cosmic neutrinos all the way back to their source. Armed with this information, scientists could learn more about the early universe, the ins and outs of black holes and more.
Besides possibly ushering in a new era of astronomy, it also opens “the doors to a new era in particle physics,” says Vladimir Papitashvili of the National Science Foundation.