A supernova is a star that ends its life with a “massive cosmic explosion” known as supernovae, hence the name supernova. Supernovas are “rare in our own galaxy”, though many have been seen in other galaxies. The last to be seen in the Milky Way was Kepler’s star back in 1604, though remnants of the Crab Nebula, which exploded in 1054 can still be seen.
The explosion of a supernova can explode matter at a rate of anywhere between 9,000 miles per second to 25,000 miles per second. The explosions produce many of the common materials that humans encounter in their everyday lives, iron for example. In fact, “heavy elements are only produced in supernovae”.
In addition to flinging materials across space, supernovae also assist in the formation of new stars. Their explosion “produce[s] a shock wave that compresses clouds of gas” that helps to create new stars.
Not all stars can become supernovae, many cool as they age and end as white dwarfs and then black dwarfs. Massive stars, ones that are larger than the sun, can become supernova, and they have been classified into two types.
In type 1, supernovas are formed by two separate stars interacting. One of these stars must be a white dwarf, and when “the mass from the companion stars falls onto the white dwarf”, the mass of the white dwarf rises above its limit and the star collapses. Here, the carbon and oxygen of the white dwarf fuse and destroy the star, leaving no evidence behind that it had ever existed.
In type 2, supernovas are formed when “their core’s fusion process runs out of fuel”, and the core collapses. Star fusion causes constant outward pressure, balanced with the star’s inward gravitational pull. When fusion begins to slow, this outward pressure drops, and the core of the star begins to condense and becomes both denser and hotter.
On the outside, these stars appear to be growing, becoming what is known as a supergiant. But on the inside, the core continues to shrink. The condensing continues until the core “is composed largely of iron, which can no longer sustain star fusion”. In a microsecond the core temperature rockets up to billions of degrees Celsius. The iron atoms are slammed together and their nuclei respond by recoiling, causing an explosion.
This explosion “can light up the sky for weeks” and leaves behind a neutron star, “a tiny core of neutrons”, as the only evidence that there had ever been a giant celestial body there. In rare occasions, if the mass is large enough, the explosion of a supernova can leave behind a black hole.
A supernova, here, is a beautiful stage in a star’s life. When this massive star explodes, it contributes to life in space by projecting elements such as iron that sustain life on Earth, as well as providing the impetus necessary for the creation of new stars. And not all supernova explosions lead to the complete death of the star. In type 2 explosions, a neutron star or black hole is left behind, yet another stage in the evolution of the star.