Hunt for the sterile neutrino

Nature News : Neutrinos like to keep to themselves. These ghostly particles are so reluctant to interact with ordinary matter that billions zip harmlessly through each person every day, and it takes giant, specialized detectors to capture even a handful of them. Now astronomers are finding hints of an even more elusive type of neutrino, one so shy that it could never be detected directly: the sterile neutrino ."The question of sterile neutrinos is absolutely crucial for nuclear particle physics and astrophysics."For more than a decade, this subatomic spectre has intrigued theorists and experimenters, but experimental efforts have had trouble catching them. Now, two observations in space—one in microwaves and the other in x rays—are raising hopes again.