Comet ISON: The Comet of the Century?

Comet ISON is coming!This newly-discovered comet may by November 2013 be an unforgettable spectacle, dominating the night sky.The comet may be even brighter than the fondly-remembered Hale-Bopp of 1997!

Comet ISON is revealed.(Image credit:E.Guido, G.Sostero and N.Howes/RAS Observatory)

C/2012 S1 (ISON) was announced on 24 September 2012.It was spotted by Vitali Nevski and Artyom Novichonok on CCD images made with a 0.4-m telescope of the International Scientific Optical Network(ISON) near Kislovodsk, Russia.The comet is currently still beyond Jupiter (6.6 Astronomical Units or AU distant)  and was a very dim Magnitude 18.8 when discovered.

Comet ISON.'s orbit and position on 25 September 2012.(Image credit:NASA)

Why are astronomers starting to get excited?

• Comet ISON’s orbit is almost perfectly parabolic.This may mean the comet originated from very far out from the Sun, in fact it may be coming straight from the Oort cloud.The Oort cloud is the vast swarm of potential comet nuclei  extending up to almost a light year from the Sun.Therefore the comet is diving sunward  into the inner Solar System for the first time and is in pristine condition.Not only is this scientifically interesting, it means it is fully loaded with frozen water, carbon monoxide, carbon dioxide, methane and ammonia which may sublimate, releasing megatonnes of dust, to form spectacular tails as the Sun’s warmth gets to work on the comet’s surface.
• The comet  will reach its closest point to the Sun, perihelion in late November 2013.Then it is expected to whizz around the Sun a mere 1.1 million km above its surface making Comet ISON one of that class of comets called  Sungrazers.
• Assuming it survives perihelion, in January 2014, Comet ISON will be at its closest to Earth, passing our planet by just 0.4 AU ( about 60 million km).Just to get it out of the way, it is not going to collide with Earth, trigger earthquakes or otherwise endanger our planet!(If this sort of thing worries you, just remember all the failed doomsday predictions for Comet Elenin.)
• Comet ISON might become a naked-eye object during November 2013 – January 2014.In fact it may even reach a negative magnitude by the end of November 2013.Some calculations suggest its brightness could eventually rival that of the full Moon.Bolder still astronomers claim it may even be visible in the daytime sky!

Comet ISON may be a once in a lifetime sight in our skies.Fingers crossed it won’t be another  Kohoutek!

(Article by Colin Johnston, Science Communicator)