The Antarctic Science Symposium in Madison, Wisconsin, started off with a few presentations about drilling technology. It’s definitely an important topic because one of the reasons scientists utilize Antarctica as a lab is the ice — either used as a detection material, or a record of climate change. However, Astronomy magazine doesn’t cover drilling technologies, so on to what you, the readers, really want to know.
For IceCube, scientists drill 8,040-foot (2,450 meters) holes into Antarctic ice and lower a string of 60 detectors into each hole. When a neutrino triggers a reaction with an atom in the ice, the newly created particle produces flashes of light, which detector modules record. // Mark Krasberg/NSF photo
Scientists are planning to install a lot of detectors in Antarctica. They’re utilizing the open skies, minimal TV and cellphone frequencies, dry air, and pristine ice. The IceCube project is an extension of a previous neutrino observatory near the South Pole called AMANDA. IceCube is on schedule for at least 3 years of operation, and after that, scientists want to build off this project by possibly creating an even larger neutrino detector. Such a plan is in the very early stages, however.
A project that is a bit further along is a radio-frequency detector in Antarctica. So, instead of detecting blue flashes of light (called Cerenkov radiation) from high-energy neutrinos — which is a simplified description of what IceCube does — this detector will look for lower-energy radio signals. Lower-energy photons have longer wavelengths, so the detectors can be spaced farther from each other. This project — the Askaryan Radio Array (ARA) — will be huge. How huge? Some 80 square kilometers — that’s 31 square miles. The ARA collaboration hopes to detect about 1,000 high-energy neutrino events each year. Right now, scientists expect to detect about two such events with IceCube. Making a bigger array means they can reach higher energies.
Why are these experiments important? Neutrinos originate in the same processes that generate cosmic rays — high-energy protons and other atomic nuclei. Scientists don’t yet know what methods create these particles. Because cosmic rays have an electromagnetic charge, they interact with galactic magnetic fields and thus change direction. Neutrinos, on the other hand, are chargeless and interact extremely weakly with matter. So, by detecting high-energy neutrinos, scientists can learn about the processes that generate cosmic rays. And bigger experiments will capture more particles.
It seems “bigger is better” isn’t just for optical telescopes, but all detectors.