By Andrew Grant
Ghostly high-energy particles from beyond the solar system have been snagged for the first time by a giant experiment buried under Antarctic ice. The sightings of the particles, called neutrinos, represent a major step toward identifying mysterious astrophysical phenomena that hurl subatomic particles across the universe at extraordinary speeds.
Neutrinos are an intriguing tool for exploring the cosmos. The wispy particles have no charge and rarely interact with matter, allowing astronomers to trace a straight path back to their source. However, neutrinos’ inertness also makes them hard to detect. Scientists are confident that alien neutrinos packing more energy than particles from any human-made accelerator are constantly pelting Earth, perhaps pointing to some of the universe’s most violent objects. But until now researchers had managed to detect only relatively puny neutrinos streaming from the atmosphere, the sun and a 1987 supernova.