Astronomy on Ice

Jonathan Strickland


In the Antarctic, there's a cubic kilometer of ice that could reveal secrets of the universe. It might sound like I'm referring to some sort of mystical guru who has chosen the most remote location on Earth to make his or her home. The real explanation is even more amazing -- it's a neutrino detector called IceCube.

Neutrinos are neutrally-charged sub-atomic particles. They have almost no mass and they are the products of some of the more spectacular cosmological events we know about, such as stars exploding. While the pathways of charged particles are impossible to determine due to deviations caused by interactions with other charged particles, neutrinos can zip through space unaffected. By detecting neutrinos and observing how much energy they have, we can determine where the neutrinos originated and learn more about our universe.

The IceCube neutrino telescope isn't just examining how neutrinos form and their behavior. It's also searching for evidence of dark matter -- the stuff that comprises the majority of matter in the universe and yet has remained undetectable.

So why build a detector at the South Pole? The ice is key. Within the ice are detectors that are the size of basketballs. They're called digital optical modules or DOMs and there are more than 5,000 of them in that cubic kilometer of ice. On top of the ice are an additional 344 detectors -- collectively they're known as IceTop.

The detectors in IceCube aren't just beneath the surface -- they're in deep, between 1,500 and 2,000 meters (or more than a mile). At that depth, the ice is under tremendous pressure, which forces out any air bubbles and makes the ice incredibly clear. It's also extremely dark. When a neutrino interacts with molecules in the ice, it creates a subatomic particle called a muon. The muons give off a blue glow, which the DOMs detect. The intensity of the light and its direction give clues about the neutrino's origins.

According to this amazing Scientific American piece (go read it - Michael Moyer makes the search of neutrinos sound poetic), the detector has found 28 neutrinos that must have originated from outside our solar system. They possessed far more energy than anything the Large Hadron Collider has produced.

I'm impressed with the ingenuity scientists have shown in their efforts to design a detector that can find something that practically has no mass, no electric charge and can pass through a planet as if nothing is there. Just imagine the things we'll learn!