What is a supernova?
Supernova or supernovas, abbreviated: SN and SNe) is a powerful and bright stellar explosion. Supernova is a transient astronomical event that occurs during the final evolutionary phases of a large star or when the nuclear fusion of a white dwarf is about to end.
In Latin, nova means “new”, which temporarily appears to be a new bright star. Adding the prefix “super-” distinguishes supernovae from ordinary nouveau, which are much less bright. The term supernova was coined in 1931 by Walter Baade and Fritz Zwicky.
Why does supernova happen?
A supernova is caused by nuclear fusion of a dying giant star. This happens when someone (the star is at least five times the mass of our sun) exits with a spectacular bang.
Large-scale stars burn huge amounts of nuclear fuel at their cores or centers. This creates tons of energy, so the center becomes very hot. Heat creates pressure, and the pressure created by the nuclear burning of a star also prevents that star from collapsing.
A star is in the balance between two opposite forces. The gravity of the star tries to squeeze the star into the smallest, hardest ball. But the nuclear fuel burning in the star’s core creates outward pressure. This external push opposes the inward gravity.
When a giant star runs out of fuel, it cools down. This causes a pressure drop. Gravity wins out, and Tara suddenly collapses. Imagine the mass of Earth is one million times larger in 15 seconds! The collapse occurs so quickly that it produces very large jerky waves that cause the outer part of the star to burst.
A very dense core is usually left behind, as well as an expanding cloud of hot gas called a nebula. A star supernova more than 10 times the size of our sun can overtake condensate objects in the universe — black holes.
The second type of supernova can occur in systems where two stars orbit each other and at least one of those stars is an Earth-sized white dwarf. A white dwarf that is released after a star, the size of our sun has run out of fuel. If one white dwarf collides with another or draws too much material from the star around it, the white dwarf may burst.
Astronomers believe that two or three supernovae happen in galaxies each century like our own Milky Way. Because there are many galaxies in the universe, astronomers observe a few hundred supernovas per year outside our galaxy. The dust of space blocks our view of most supernovas within the Milky Way.
How bright are Supernovas?
These spectacular events can be so bright that they brighten their entire galaxies even for a few days or months. They can be seen in the universe.
How do scientists study supernova?
Scientists have learned a lot about the universe by studying supernovas. They use the second type of supernova (which includes white dwarfs) like a ruler to measure distances in space.
They also know that stars are the factories of the universe. Stars produce the chemical elements necessary to make everything in our universe. At their core, stars convert simple elements into heavier elements such as hydrogen. These heavy elements, such as carbon and nitrogen, are essential elements for life.
Only massive stars can form heavy elements such as gold, silver, and uranium. When an explosive supernova occurs, the stars distribute the elements stored in space.
NASA scientists use several different types of telescopes and then study supernovas. An example is the NuSTAR (Nuclear Spectroscopic Telescope Array) mission, which uses X-ray vision to probe the universe. NuSTAR is helping scientists observe supernovae and young nebulae to find out what happens during and after these spectacular eruptions.