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Spacecraft passes through 350-million-mile comet tail

Hubble Space Telescope image of comet Hyakutake  

April 6, 2000
Web posted at: 9:54 AM EDT (1354 GMT)

LONDON (Reuters) -- A chance encounter between the spacecraft Ulysses and the wake of a speeding comet has helped scientists to identify the longest comet tail every recorded.

The discovery by two independent teams of scientists, reported in the science journal Nature on Wednesday, could open up a new way of studying the heavenly bodies that astronomers believe may hold the secrets of our solar system.

"This tail extends more than half a billion kilometers (300 million miles). That's more than three times the distance from the Earth to the sun. It's just unbelievable," Nathan Schwadron, of the University of Michigan's College of Engineering, said in a statement.


The scientists knew something strange had occurred on May 2, 1996, when Ulysses, the spacecraft launched in 1990 by NASA and the European Space Agency to study solar winds, radioed data back to Earth.

Everything went haywire for a few hours.

The solar winds, a stream of particles flowing from the sun, went calm. The spacecraft was then bombarded by charged particles from what turned out to be the wake, or ionized vapor tail, of what scientists calculated could only be Comet Hyakutake, which was in another part of the solar system.

The encounter was amazing because the tail of the comet turned out to be much bigger than astronomers expected. It was also only the fourth time a spacecraft had crossed paths with a comet tail, giving scientists an opportunity to identify chemicals in the wake.

"It brings up a whole new way to study comets, and I think opens up a whole new area of science," Schwadron said.

Artist's concept of the Ulysses spacecraft shortly after deployment from the space shuttle payload bay  

If scientists had better data for instruments designed to intercept long tails of comet dust, Schwadron and his colleagues in Michigan and researchers at the International Space Science Institute in Switzerland believe it would be possible to learn how stars have processed material over time.

It could also help to answer cosmic questions such as the age of the universe and how it was formed.

"Finding and identifying the comet's tail is only the beginning. Now we can learn a great deal more about what conditions are like in comet tails by studying data from instruments that have actually been there," said Geraint Jones, of Imperial College in London, who reported the finding of the comet tail in a separate study in Nature.

Jones and researchers at Queen Mary and Westfield College in London said the tail is 570 million kilometers (350 million miles) long. It is also only the fourth comet tail encountered by a spacecraft and the one furthest from the sun.

Comet Hyakutake was discovered in 1996 and named for the Japanese amateur astronomer who located it.

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