[Science Report]:Comet LINEAR


This is the VOA SpecialEnglish Science Report.

A space object of frozen gas and rock broke into many pieces oneyear ago. The Hubble Space Telescope and telescopes on Earthrecorded the death of the comet named LINEAR. Now scientists havereported what they learned from the information provided by thetelescopes.

Hal Weaver is an astronomer at the Johns Hopkins University inBaltimore, Maryland. His study of LINEAR was published in themagazine Science. Mister Weaver says the break up of LINEAR hastaught scientists about the period when Earth and the solar systemformed. LINEAR began forming at that same time -- aboutfour-and-one-half-thousand-million years ago.

Mister Weaver says watching the death of the comet was likelooking back in time. He says as LINEAR's pieces fell awayscientists 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. Hesays the comet was not close to any large object. This means LINEARwas not torn apart by a gravitational force.

Mister Weaver says frozen carbon monoxide gas probably was notinvolved. This gas can cause a sudden pressure increase in thecenter of a comet. But Mister Weaver says LINEAR had fifty timesless carbon monoxide than comets Hale-Bopp and Hyakutake.

Mister Weaver says there is another mystery connected withLINEAR. He says the comet's estimated mass was aboutthree-hundred-thousand-million kilograms. After LINEAR broke upscientists measured the mass of the sixteen large pieces thatremained. They also measured the mass of a huge area of dust left bythe comet.

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

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

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

This VOA Special English Science Report was written by CatyWeaver.

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