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SCIENCE REPORT - Comet LINEAR

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This is the VOA Special English Science Report.

A space object of frozen gas and rock broke into many pieces one year ago. The Hubble Space Telescope and telescopes on Earth recorded the death of the comet named LINEAR. Now scientists have reported what they learned from the information provided by the telescopes.

Hal Weaver is an astronomer at the Johns Hopkins University in Baltimore, Maryland. His study of LINEAR was published in the magazine Science. Mister Weaver says the break up of LINEAR has taught scientists about the period when Earth and the solar system formed. LINEAR began forming at that same time -- about four-and-one-half-thousand-million years ago.

Mister Weaver says watching the death of the comet was like looking back in time. He says as LINEAR's pieces fell away scientists could see how the comet may have developed.

Mister Weaver says scientists are not sure why LINEAR broke up. He says no other comet has fallen apart in the way LINEAR did. He says the comet was not close to any large object. This means LINEAR was not torn apart by a gravitational force.

Mister Weaver says frozen carbon monoxide gas probably was not involved. This gas can cause a sudden pressure increase in the center of a comet. But Mister Weaver says LINEAR had fifty times less carbon monoxide than comets Hale-Bopp and Hyakutake.

Mister Weaver says there is another mystery connected with LINEAR. He says the comet's estimated mass was about three-hundred-thousand-million kilograms. After LINEAR broke up scientists measured the mass of the sixteen large pieces that remained. They also measured the mass of a huge area of dust left by the comet.

The combined weight of the pieces and the dust was just over three-thousand-million kilograms. That is about one-hundred times less than the mass of the comet when it was whole.

Mister Weaver thinks the missing mass may be in pieces no bigger than fifty meters across. Hubble and other telescopes would not be able to see these pieces.

Comet pieces of such size are unusual. Scientists believe gravity pulls together much larger objects to form comets. Mister Weaver says the existence of medium-size pieces may change that theory.

This VOA Special English Science Report was written by Caty Weaver.

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