Comet ISON is speeding toward the sun. Ison, the comet of the century, is brightening, but not throwing off fireworks. Skywatchers say the comet's path is like riding a "bucking bronco" in space. Astronomers are waiting to see if Comet ISON survives its passage past with the Sun. Comet Ison will reach its closest approach to the sun today.

Comet Ison was discovered on September 21, 2012 by Vitali Nevski and Artyom Novichonok. It is classified as a "sungrazer."

Comet ISON, the "comet of the century," may be destroyed by Sun's heat and gravitational tug before it has a chance to light up the skies. Some scientists say Comet ISON is already beginning to buckle.

Associate director of the Britain's Jodrell Bank Observatory, Prof Tim O'Brien, said: "It's like throwing a snowball into fire. It's going to be tough for it to survive. But luckily, it's a big object and it moves fast, so it won't spend too much time close to the Sun. There is a lot of uncertainty."

Comet Ison originated at the Oort Cloud, which is in the icy region at the furthest reaches of our Solar System. The comet of the century has been speeding toward the Sun at over a million kilometres an hour. Ison could break up completely. If it doesn't break up it will light the sky during December.

Prof Mark Bailey, from Armagh Observatory in Northern Ireland, said: "It's going to be exposed to the worst that the Sun can throw at it.  It will be getting exposed to more and more intense solar heat, and that will start to sublimate the ices (turning them into gas) at an increasing rate."

Scientists are concerned that ISON could go out the same way as Comet Lovejoy. That comet broke apart after it passed near the Sun in 2011. Comet ISON may be large enough to survive the solar pass.

Dr Robert Massey from the Royal Astronomical Society said "If it survives, the best chance of seeing it will be in early December. I very much doubt Ison is going to be the sort of object where you go out in the morning, just before sunrise, and see this amazingly spectacular thing across the night sky. It's much more likely, at the optimistic end, that it's visible with the naked eye, and with binoculars - you could see the comet's head and a nice long tail coming from that."