What is a supernova? A supernova is “a star that suddenly increases in brightness because of an explosion ejecting most of its mass.” Definition taken from the Canadian Oxford dictionary (1998).
The life of a star of one solar mass (the size of our sun) goes through nine stages in all.
Stage 1- A star is born in a place of high density Nebula (cluster of stars) and is made of gas and dust, and forms a sphere under its own gravity.
Stage 2 – The gas and dust will begin to heat up and start to glow forming Protostars. If a protostar contains enough matter, it can reach a temperature of 15 million °C.
Stage 3 – When it reaches this temperature, hydrogen can fuse to form helium.
Stage 4 – Next the star starts to release energy and starts to shine. Now it can be called a Main Sequence star.
Stage 5 – The star will stay in Main Sequence for about 10 billion years, until all of its hydrogen has been transformed to helium.
Stage 6 – The star’s helium core starts to shrink even more and reactions start to take place in a shell around the star’s core.
Stage 7 - The core is so hot that the helium starts to fuse to make carbon. The outer layers start to grow, cool down and the star doesn’t shine as brightly. The star can now be called a Red Giant.
Stage 8 – The star’s helium core runs out, and the outer layers slip away from the core as a shell of gas, the gas that envelopes the core is called a Planetary Nebula.
Stage 9 - The core that’s left (that’s 80% of the original star) is now in its last stages. The star’s core now becomes a White Dwarf. The star eventually cools down and dims. When the star stops shining, it is referred to as a Black Dwarf.
(These nine stages are adapted from http://www.astro.keele.ac.uk/workx/starlife/)
The picture below shows the process in which a star goes Supernova.
(image taken from http://astrosun2.astro.cornell.edu/academics/courses/astro201/images)
When the stars nuclear fuel has been depleted and it is no longer maintained by the release of nuclear energy, the star goes Supernova. When a star goes Supernova it can be billions of times brighter than the Sun. When a star is in supernova it can release more thermal energy in 10 seconds than the sun will produce in its entire lifetime.
Sometimes a larger star that has gone supernova will turn into a black hole. A Black hole has so much gravity that it will suck up almost anything that comes close to it. If are sun goes supernova and turnes into a black hole, we would all most likely die.
In Latin the word "nova" means "new". Some people think that a supernova is a new star that has just been formed because it is shining so bright. But it really represents the death of a star.
It is not thought that our Sun will go Supernova, but if it did it would shoot out a cloud of dust and gas. It would also give off radiation and in the end destroy our entire solar system. As you can see this would be a great reason to start terraforming, so we could slowly move outwards in the solar system. If we did it in time we could maybe be able to reach the closest galaxy.
There have been many supernovas. A few of the more famous ones are:
1006 - an extremely bright supernova, historical accounts found all over the world - Egypt, Iraq, China, Italy as well as many other places- 1054 - a large supernova resulting in the formation of the Crab Nebula
1181 - supernova in Cassiopeia, noted in Asia
1572 - another supernova in Cassiopeia
1604 - supernova in Ophiuchs, last supernova oberved in the Milky Way
1885 - supernova in the Andromeda Galaxy
1987 - supernova in the Large Magellanic Cloud
