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Comet Lulin…. not as deadly as portrayed

Space scientists from the University of Leicester are keeping a close eye on a ‘green comet’ fast approaching the Earth – reaching its nearest point to us on February 24

Comet Lulin will streak by the earth within 38 million miles – 160 times farther than the moon -and is expected to be visible to the naked eye. Discovered only a year ago, the comet gains its green colour from poisonous cyanogen and diatomic carbon gases in its atmosphere.

This will be the comet’s first visit to the Earth’s inner solar system- and will enable the team from the University of Leicester to gain valuable insights into the comet.

They are using NASA’s Swift satellite to monitor Comet Lulin as it closes on Earth. The spacecraft has recorded simultaneous ultraviolet and X-ray images of a comet.

“Swift is the ideal spacecraft with which to observe this comet”, said Jenny Carter, a scientist working with Dr Andrew Read at the University of Leicester, UK. “We alerted the Swift team that the comet might be visible” said Dr Read “and they quickly responded to take images using both the X-ray (XRT) and Ultraviolet/Optical Telescopes (UVOT) on-board.”

Dr Julian Osborne, leader of the Swift project at Leicester, said ‘The wonderful ease of scheduling of Swift and its joint UV and X-ray capability make Swift the observatory of choice for observations like these.’

Carter added: “It is important to carry out these observations as they give us clues about the origin of comets and the solar system”.

As the University of Leicester has played a major role in developing Swift’s X-Ray Telescope and is an important centre for the study of high-energy emission from objects within our Solar System, it is an ideal place for this study to be carried out.

A comet is a clump of frozen gases mixed with dust. These “dirty snowballs” cast off gas and dust whenever they venture near the sun. Comet Lulin, which is formally known as C/2007 N3, was discovered last year by astronomers at Taiwan’s Lulin Observatory.

On Jan. 28, Swift trained its Ultraviolet/Optical Telescope and X-Ray Telescope on Comet Lulin. “The comet is quite active,” said team member Dennis Bodewits, a NASA Postdoctoral Fellow at the Goddard Space Flight Center in Greenbelt, Maryland, USA. “The UVOT data show that Lulin was shedding nearly 800 gallons of water each second.” That’s enough to fill an Olympic-size swimming pool in less than 15 minutes.

Swift can’t see water directly. But ultraviolet light from the sun quickly breaks apart water molecules into hydrogen atoms and hydroxyl (OH) molecules. Swift’s UVOT detects the hydroxyl molecules, and its images of Lulin reveal a hydroxyl cloud spanning nearly 250,000 miles, or slightly greater than the distance between Earth and the moon.

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