Ghosts in the machine
Although to date they've managed to identify only two sources of neutrinos from beyond Earth, physicists continue to search for these elusive particles.
Every second, billions of neutrinos fly through your body as if it weren't there. Even planet Earth poses little barrier to these tiny particles. Neutrinos interact so rarely with normal matter that huge detectors are needed to trap just a few. Only two cosmic sources of neutrinos have been pinned down so far: the interior of the Sun, where nuclear fusion reactions produce prodigious quantities of neutrinos; and Supernova 1987A, in which the neutrinos formed during the collapse of a massive star...