Ten interesting facts about Comet ISON

As astronomers speculate the fate of Comet ISON, here are a few fun facts about the much anticipated comet also called the `Comet of the century`.

By Liji Varghese | Last Updated: Dec 02, 2013, 14:44 PM IST

Liji Varghese

As astronomers speculate the fate of Comet ISON, here are a few fun facts about the much anticipated comet also called the `Comet of the century`.

When and who discovered the comet?

Comet ISON was discovered by on 21 September 2012 by two amateur Russian astronomers Vitali Nevski and Artyom Novichonok.

Why the name ISON?

The comet was discovered using a 0.4-meter (16 in) reflector of the International Scientific Optical Network (ISON) near Kislovodsk, Russia, and so is popularly known as Comet ISON.

However officially it is named C/2012 S1 where the "C" indicates that it is non-periodic, followed by the year of discovery. The "S" represents the half-month of discovery—in the case of C/2012 S1, the second half of September—and the number "1" shows that this was the first comet found in that half month.

Why is it called a ‘sungrazer’?

A ‘sungrazing’ comet is a comet that passes extremely close to the Sun at perihelion.

ISON is among the very few comets to go through the corona of the sun. It will pass the Sun at a distance of just 1.2 million kilometres. If the comet survives the close encounter, it may emerge as an easily spotted early December sky. Alternatively the comet’s nucleus may disintegrate into a cloud or fizzle out.

Where has it come from?

ISON comes from an Oort cloud, a loose nebulous sphere containing billions of icy, rocky objects on the very edge of the solar system, where it has been for the last 4.6 billion years. ISON was quiet recently knocked out of the Oort cloud and began its trip towards the sun, which is nearing its end.

Is this ISON`s first trip to the solar system?

Yes, this is indeed ISON`s first trip to the inner solar system. The trajectory appears to be hyperbolic, which suggests that it is a dynamically new comet coming freshly from the Oort cloud. Once it swings back out, it isn’t going to come back either.

How big is the comet?

According to the observations made by NASA`s Hubble Space Telescope in April this year suggested that ISON had a nucleus not bigger than 3 to 4 miles despite being a bright and active comet. The head of the comet, also called a coma, was found to be 3,100 miles across and the tail to be more than 57,000 miles long.

What will be the fate of the comet?

So far, there is no clarity on the fate of the comet as it prepares for the showdown with the sun on Thanksgiving, November 28. However, scientists are looking at three possible scenarios.

First, it can be pulled apart by the Sun`s gravitation forcing it to explode.

The second possible scenario is that it simply fizzles as the gases and the ice may vaporise due to the extreme heat of the sun.

The third scenario that the scientists are expecting is that the comet flies through the corona, which would eventually heat up the gases just enough to produce a huge tail.

Will the comet have any impact on Earth?

No, whatever the fate of the comet it would not impact Earth. According to NASA, the closest approach to Earth will be approximately 40 million miles on December 26, 2013.

What happens if it survives the solar flare?

If the comet survives the fury of the Sun, the comet will help unlock the mysteries of the solar system as scientists hope to analyse the chemical composition of the ices in ISON. They are also hoping to study water signature and observe the chemical precursors of amino acids - the molecules that form the building blocks of life.

Will it be visible post encounter with the Sun?

The comet will reach the perihelion (closest approach to the sun) approximately around 1835 GMT on Thursday, November 28.

If it survives, it will be visible to the naked eye early December to people in the northern hemisphere.