Tuesday 20 March 2018

Stellar display ahead if comet survives brush with sun

Adam Withnall

FOR the past year, scientists have been tracking Ison's movement as it hurtles towards the inner solar system and, on Thursday, it is set to pass through the sun's corona.

The comet is around 4.6 billion years old – forming at the very beginning of the solar system, and has been sitting quietly in the outer reaches of the sun's gravitational field for almost all that time.

Relatively recently, Ison was knocked out of the distant Oort cloud and began its journey towards the sun. That light-year-long trip is nearly over, and astronomers still don't know if it will survive it.

Speaking to a BBC 'Horizon' special on the comet last night, Dr Matthew Knight said there were three possible scenarios for what could happen on November 28.

Scenario one is for the comet to be pulled apart by the gravitational force of the sun, stretching it beyond breaking point and forcing it to explode as it leaves the corona. Ison is an average-to-small sized comet, making this scenario a real risk.

Scenario two is for Ison to succumb to the heat of the sun. Comets are largely made up of ice and other frozen gases, and while this one is a "star-grazer", expected to only pass the sun once, it could experience heat of up to 2,000C.

The third and final scenario is the one Dr Knight, who has studied Ison for a year and recently became the first scientist to ever capture it on camera, is hoping for.

As the comet flies through the corona, the gases could be heated up and ignited just enough to produce a tail burning off, but not enough to destroy it entirely.

If this happens, millions of people in Earth's northern hemisphere will be able to witness an extraordinary display in the night sky.

Irish Independent

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