On September 21st last year two Russian astronomers, Vitali Nevski and Artyom Novichonok discovered a new comet that's creating a buzz of anticipation around the world. It may turn out to be the most spectacular comet to grace our skies in centuries. Nevertheless, astronomers are pulling in the reins on the world’s excitement, as Comet ISON may also break apart before putting on an amazing show. Luckily we don't have to wait too long to find out, as we should be able to see it with the naked eye by October.
There are a couple of things that make this particular comet unique the first being its name. Most comets are named after the person/s that discovered it, like Halley's Comet and Comet Hale-Bopp. Instead of being named Comet Nevski-Novichonok after its discoverers, the world's media has latched onto ISON - the acronym for the International Scientific Optical Network - which is the organisation that Nevski and Novichonok were working for when they made the discovery. Unfortunately for the Russian astronomers, the name has stuck. The other somewhat unique feature of ISON is that, according to NASA, it is likely a new comet, meaning that this will be its first time passing through our solar system.
You may be wondering why this particular comet has the potential to be especially bright. Firstly, ISON is considered to be a “sungrazing” comet, which means it will pass very close to the sun's surface. Because of the close proximity to the sun, the comet will become extremely hot. This allows more of the materials within it to explode burn and evaporate out and off of it, therefore potentially producing a very long and bright tail. Since ISON will be approaching the sun for the first time, it will also be fully loaded with ice and dust, adding to the possibility that we'll be treated to a wonderful display. However, NASA astronomers warn it may all amount to very little. The gravitational forces acting on the comet as it approaches perihelion (its closest approach to the sun) will be so intense, that they could cause it to break apart and fizzle out. If ISON manages to remain intact, predictions are that around perihelion in late November, the comet could become brighter than the full moon and will be visible near the sun in broad daylight. NASA also suggests a third, and exciting outcome: a partial break-up of the comet that might give it a “string-of-pearls” appearance, especially when viewed through telescopes.
After perihelion, ISON will gradually dim but will continue to be visible until mid-January 2014; and at the same time, the Earth will pass through the comet's orbit, increasing meteors in our evening skies. Here is a video by NASA showing the comet's expected path through our solar system and comparing ISON to other comets recently visible from earth:
As excited as sky-watchers are about the potential brilliance of this celestial encounter, comets are notoriously fickle and many before have not lived-up to expectations, hence astronomers the world over seem to be cautiously optimistic about ISON's potential for dazzling us in late 2013. For the rest of us, holding thumbs and hoping for the best is all we can do and if we're lucky enough, we’ll be witness to a once-in-a-lifetime cosmic event.