Thick clouds of interstellar dust hide some supernovas, but astronomers can detect those by the radio waves that the supernova emits. Supernovas occur in all galaxies, not just the Milky Way. Supernovas that occur outside the Milky Way are bright enough to stand out against the other stars in the galaxy. However, they are usually not bright enough to pick out without a telescope . A typical supernova can produce as much light and other forms of electromagnetic radiation as billions of stars.
Electromagnetic radiation is energy carried through space by electric and magnetic waves.
The length of these waves determines the properties of the radiation. In addition to the radiation energy a supernova produces, the force of the explosion releases ten times more energy into the motion of the particles that the explosion blows outward. These tiny particles, called neutrinos, carry away a hundred times more energy than the electromagnetic radiation. Astronomers discover about ten supernovas in distant galaxies each year. The mass of a star determines whether it will end its life in a supernova explosion.