what is supernova

A supernova is a powerful and luminous 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 basic mechanisms that can trigger a supernova: the sudden re-ignition of nuclear fusion in a white dwarf, or the sudden gravitational collapse of a massive stars core. When a massive star runs out of fuel, it cools off, causing the pressure to drop. Gravity then takes over, and the star suddenly collapses, creating enormous shock waves that cause the outer part of the star to explode. The resulting explosion is a supernova, which can briefly outshine entire galaxies and radiate more energy than our sun. Supernovae are considered one of the original sources of the elements heavier than iron in the Universe, and they create new atomic nuclei in a process called nucleosynthesis. Scientists have identified several types of supernova, and they use them to measure distances in space. Supernovae are difficult to see in our own Milky Way galaxy because dust blocks our view, but they can be seen across the universe.