There is a scientific instrument called the IceCube Neutrino Observatory spanning a cubic kilometer of Antarctic ice more than 1.4 kilometers below the surface. This observatory is designed to detect neutrinos that pass through the instrument and interact with matter nearby. This is extremely rare because, although neutrinos are extremely common, they have a very low chance of interacting with matter.
The observatory was built by boring holes more than 2.5 kilometers deep and dangling a chain of highly sensitive optical detectors down the hole. It’s really fascinating. See here, for example.
This week it was announced that last fall IceCube detected a neutrino. This event led to numerous other observatories looking in the direction from which the neutrino was known to have come. It’s now known that the neutrino very likely came from a blazar – a quasar that has one of its jets of matter that travels at near relativistic speeds pointing at us. This is the third object that we have managed to trace a neutrino back to. Check out “The IceCube Neutrino Detector at the South Pole Hits Paydirt” for more details.