Supernovae

I'm pretty sure most people have heard of supernovae at some point, even if they aren't educated on the topic. After all, it's such a cool name. Supernova. Sounds like some villain's name or some special attack of some sort!

Anyway, getting back on topic, a supernova is categorised as a transient astronomical event, which means that it is a phenomenon that takes a relatively minute timescale compared to the other processes that happen in outer space such as the formation of galaxies which take millions, if not billions, of years. Transient types only last on timescales of seconds to a few years.

Supernova uses the Latin word "nova"  which means new. This is because there is a sudden bright burst of light that appears which looks like a new star. But this is actually caused when a star reaches the end of its life (the last stellar evolutionary stages) and explodes. It uses the prefix of "super-" because it is much brighter than a nova, which is another phenomenon that is caused by an interaction between two stars which causes a flare-up that shows a much brighter light than both of the stars in the interaction.

The explosion of a supernova is known to be triggered by one of two mechanisms: the gravitational collapse of a massive star's core or the re-ignition of nuclear fusion in a degenerate star (one that is endpoint of a star's evolution and includes white dwarves and neutron stars). The re-ignition is called 'thermal runaway' and happens when he white dwarf accumulates enough material from another star by either colliding with another white dwarf or pulling away material with gravitational force. This material is then used to 'warm up' its core temperature enough to ignite carbon fusion and through this it achieves runaway nuclear fusion. This means that the reaction releases heat and in turn the heat will increase the rate of reaction. So this circular trend will start to release so much energy that the star burns bright enough for us to see it millions of light years away. The collapse of the massive star's core is normally due to the nuclear fusion of the star being unable to hold the core up against its own gravity, resulting in the star expelling its own outer layers at speeds of 30,000 m/s, which is a tenth of the speed of light. The subsequent stages of the star may be its transformation into a black hole.

But its not all destruction and violence. The main source of elements heavier than nitrogen are supernovae, mainly because normal stars cannot reach the core temperatures needed in order to fuse elements and make elements such as carbon, which most of the lifeforms on Earth are made of. They also eject waves of material and these materials are rich in different elements so they enrich the sites of star formation. The kinetic energy of supernova remnants also allow them to compress nearby dense molecular clouds in space and form new stars. So, you could also supernovae the 'creator of life'. And there is something incredibly poetic in 'breathing' life into the universe in your last moments, just before death. 

But then again, having a supernova occur nearby could also expose our atmosphere to powerful gamma rays which convert nitrogen to nitrogen oxides which deplete the ozone layer and leave us on the surface to be exposed to harmful UV solar radiation. This has been theorised to be the cause of the death of 60% of marine life on Earth 430 million years ago, so maybe not so friendly...