A newbies guide to Ison part 3

How fast is Ison?

Ison is moving fast! As of September she is traveling at approximately 107826 kph (67,000 mph), at this speed it would take Ison just 10 seconds to travel the entire length of the M1 motorway! 

But that's not the whole story, Ison is accelerating. As the comet gets closer to the sun, the effect of the suns gravity is stronger and will cause Ison to speed up. In December when Ison reaches the sun, the sun will "slingshot" her back out into the solar system at tremendous speed. Remember when you were a kid running up to a lamp post, grabbing hold of it and being swung round? Remember how you suddenly speed up, well swap the lamppost for the sun and you for Ison! (If you don't remember doing it, go and have a go now!)

When Ison goes through this slingshot around the sun we expect her to reach speeds of up to 1,359,895 kph (845,000 mph)! At this speed the M1 would take just 0.8 seconds, it is rumoured that Jeremy Clarkson has been seen building a giant harpoon to try and capture Ison.......

Where did Ison come from?

We believe Ison came from the Oort cloud. Our solar system sits inside a large ball shaped cloud of ice and rocks. This is the Oort cloud and is generally considered to be the boundary of the solar system and the birth place of most comets. 

You may notice on the picture above that the cloud has two parts, the inner cloud and the outer cloud. Imagine a football with a dinner plate inside. The outer cloud is where we think Ison came from. The Oort cloud contains trillions of frozen objects, mainly water, ammonia and methane.

The edge of the Oort cloud is about one light year away from the sun, around 22,5000,000,000,000 km (13,950,000,000,000 miles) and at this distance the effect of the suns gravity is very weak. It’s thought that the gravitational effect from our neighbouring stars dislodge chunks of ice and push them in to our solar system where they become comets, like Ison. Very little is known about the Oort cloud in fact most of it is theory, we have yet to send a space probe there! 

What is Ison's mass?

Just like size, it's not easy to work out the mass of comets! Many astronomers are reluctant to even take a guess, but we will! We have estimated Ison to be 3,175,146,590 kg. This estimate was reached by a mean average of estimates from 11 BCRS members. All the estimates were within a 9% range, so we are quietly confident with its accuracy. That said, new data is coming in daily so we might revise this figure in the future, but we would be surprised if it was by much! 

How close to earth will Ison get?

At its closest point Ison will be 69,000,000 km (39,900,000 miles) from earth on the 26th of December.

A newbie's guide to Ison part 1

What is Ison?

Ison is a comet which was discovered on the 21st of September 2012 by two astronomers called Vitali Nevski and Artyom Novichonok from Russia.

Its been a long time since I was at school, remind me what a comet is again?

A comet is a large chunk of ice, dust and rock hurtling though space. Imagine making a snowball out of the slush you get at the side of the road during winter and you'll get the idea!

Why is Ison causing so much fuss?

Ison is what's called a "sungrazing comet" basically this means as it travels through our solar system it will pass close to the sun. As it gets close to the sun it will become heated by the sun and start to vaporize which creates the characteristic comet tail. The closer Ison gets the brighter and more dramatic the comet will become. Due to Ison's path and size, it is predicted to produce one of the most spectacular astronomical shows in living memory!

How big is Ison?

Judging the size of comets is tricky at best, but the current estimate is about 5km (3 miles) in diameter. This estimate comes from data obtained by NASA's Swift satellite, which has been watching the amount of debris (dust and ice) that is ejected from Ison as it travels through space. 5km sounds big but to put this in to perspective the Hale-Bopp comet of 1997 was 30km in diameter! The comet itself is not the main attraction for most people, its the tail which steals the show and this is currently 3700km (2300 miles) long and growing as it gets closer to the sun!