Scientists can use the same technique to find exploding stars. The most common type of neutrino forms within the cores of stars like our sun. When the star “dies,” it can explode into a bright ball called a supernova. Like black holes, supernovas are difficult to observe. The sky is big and only two or three supernovas may occur in our galaxy every century. What’s more, their explosions may last only a few seconds. But like black holes, supernovas eject streams of neutrinos, which can serve as a sort of energy “fingerprint” by which the supernova can be traced.