The comet's closest approach to the sun (684,000 miles or 1.1 million kilometers), called the perihelion, will take place at 1844 GMT (around 12.15 am in India on Friday).
Comet ISON was discovered in September last year by two amateur astronomers of Russia, Vitali Nevski and Artyom Novichonok. Scientists from across the world have tracked the comet's progress ever since to see whether it would survive its tryst with the blazing sun and emerge as the comet of the century.
The comet comes from the Oort cloud, a vast cloud made of icy objects
But can the comet, a 1-kilometre wide lump of rock and ice, survive the heat of the sun that will roast it to an incredible 3000-degree Celsius? The comet may either be blown up in dust and gases or break up into smaller pieces of rocks or still may survive and reappear on the other side in December.
On Wednesday, Ison's speed was 115 kmph and by the time it approaches the sun on Thursday, it will be travelling at 370 kmph.
Another big attraction of ISON besides its brave tryst with the sun is its background. It originates from the Oort cloud, a vast cloud made of icy objects that surround the solar system. It is a remnant from the original particles that formed the solar system 4.5 billion years ago.