What is Ison?
Ison is a comet which was discovered on the 21st of September 2012 by two astronomers called Vitali Nevski and Artyom Novichonok from Russia.
Its been a long time since I was at school, remind me what a comet is again?
A comet is a large chunk of ice, dust and rock hurtling though space. Imagine making a snowball out of the slush you get at the side of the road during winter and you'll get the idea!
Why is Ison causing so much fuss?
Ison is what's called a "sungrazing comet" basically this means as it travels through our solar system it will pass close to the sun. As it gets close to the sun it will become heated by the sun and start to vaporize which creates the characteristic comet tail. The closer Ison gets the brighter and more dramatic the comet will become. Due to Ison's path and size, it is predicted to produce one of the most spectacular astronomical shows in living memory!
How big is Ison?
Judging the size of comets is tricky at best, but the current estimate is about 5km (3 miles) in diameter. This estimate comes from data obtained by NASA's Swift satellite, which has been watching the amount of debris (dust and ice) that is ejected from Ison as it travels through space. 5km sounds big but to put this in to perspective the Hale-Bopp comet of 1997 was 30km in diameter! The comet itself is not the main attraction for most people, its the tail which steals the show and this is currently 3700km (2300 miles) long and growing as it gets closer to the sun!
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