Scientists at the IceCube South Pole Neutrino Observatory have captured the highest energy neutrinos that have ever been seen. And to find them, they used faster-than-light particles and a hole drilled 1.5 miles under the Antarctic ice.
Neutrinos are those spooky massless subatomic particles that can pass through normal matter like a ghost. They can pull off this trick because they don’t carry an electric charge, thus making them immune to electromagnetic forces that influence charged particles like electrons and protons.
These particles come into existence in a number of ways, including the nuclear reactions of stars. And in fact, the sun is where most of the neutrinos that pass through the Earth come from. But the discovery of two ultra-high-density neutrinos in Antarctica (dubbed “Bert” and “Ernie”) indicates they may also originate from supernova gamma-ray bursts or active galactic nuclei (the jets that spew out from supermassive black holes) — and that they can reach Earth after traveling spectacularly long distances.
To make this discovery, the scientists used IceCube, the world’s largest neutrino detector — a facility that encompasses an entire cubic kilometer of ice. By drilling to a depth of 1 to 1.5 miles, it’s easier for the scientists to see the flash of light from a neutrino reaction.
Phil Plait explains:
This [detector] relies on the idea that a neutrino passing through ice can create a shower of subatomic particles, like shrapnel. These particles scream out from the collision and can actually travel faster than light through the ice. I know, this sounds impossible, but light speed is the Universal limit when it’s traveling through a vacuum. Light slows down when passing through air, or liquid, or matter. So a subatomic particle can travel faster than light through matter, while still traveling slower than light does in a vacuum.
When this happens, the particle creates a shock wave, just like a sonic boom is created when something travels faster than sound. In this case, though, it’s not a sonic boom, but a photonic boom, a shock wave of light. This creates a faint blue flash called Cherenkov radiation, and that can be seen using very sensitive detectors.
The scientists say they’re 99% certain that these neutrinos are not from some background source; ideally, they’d like to be at least 99.7% sure — so work continues.
Check out the entire paper, “First observation of PeV-energy neutrinos with IceCube.” Oh, and as you can see from this screen grab of the paper, several people collaborated on the project:
Images: IceCube Project.