One of the most eagerly awaited comets of all time, Comet ISON, has been captured by Hubble as it races through the Solar System for a rendezvous with the Sun.
Astronomers around the world are hoping for a spectacular display at the end of the year – but the NASA/ESA space telescope has been studying the cosmic visitor already.
The Hubble team have just released a movie made up from images taken by the orbiting telescope on 8 May as the comet was still travelling between the orbits of Jupiter and Mars and 650 million km (403 million miles) from Earth.
Despite the distance, the comet, which is already sporting a tail, can be seen moving across the starry background in the 43 minutes over which exposures were taken. It travelled 55,000 km (34,000 miles) in that time.
The movie of the comet taken by Hubble. Credit: Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)
The tail is produced by a warming of the comet’s icy head, or nucleus, which releases gases into space. These are swept away from the nucleus by the pressure of the solar wind.
The comet, discovered from Russia by the International Scientific Optical Network (ISON) on 21 September. It is officially labelled C/2012 S1 (ISON).
Calculations show that Comet ISON will pass less than two million km from the Sun at perihelion on 28 November. Its brightness then has been predicted to reach anything between -11 and -16 which could make it brighter than the Full Moon.
But comet behaviour is notoriously difficult to predict and there is also the danger that its close pass by the Sun could cause the comet to break up.
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