A supernova is a powerful and luminous explosion of a star. It occurs during the last evolutionary stages of a massive star or when a white dwarf is triggered into runaway nuclear fusion. There are two basic mechanisms that trigger most supernovae: the sudden re-ignition of nuclear fusion in a white dwarf, or the sudden gravitational collapse of a massive stars core. The explosion of a supernova is so bright that it can briefly outshine an entire galaxy and radiate more energy than our sun.

There are two main types of supernovae: thermonuclear runaway or core-collapse. The first type happens in binary star systems where at least one star is a white dwarf, and theyre typically called Type Ia SNe. The second type happens when stars with masses greater than 8 times that of the sun run out of fuel and collapse under their own gravity.

Supernovae are considered one of the original sources of the elements heavier than iron in the Universe. They create new atomic nuclei in a process called nucleosynthesis. Even the iron in our blood can be traced back to supernovae or similar cosmic explosions from long before our Sun had formed.

Supernovae are not very common, and astronomers believe that about two or three supernovae occur each century in galaxies like our own Milky Way. Because the universe contains so many galaxies, astronomers observe a few hundred supernovae per year outside our galaxy.

Scientists study supernovae using different types of telescopes, such as the NuSTAR (Nuclear Spectroscopic Telescope Array) and the Hubble Space Telescope. They use supernovae to measure distances in space and learn about the universe.

In summary, a supernova is a powerful explosion of a star that occurs during the last evolutionary stages of a massive star or when a white dwarf is triggered into runaway nuclear fusion. There are two main types of supernovae, and they are considered one of the original sources of the elements heavier than iron in the Universe. Supernovae are not very common, and scientists study them to learn about the universe.