学位英语

Meteors and Comets

Sometimes in the month of November, a special event happens in the sky that observers may remember for a lifetime. (1) It is a meteor storm. Meteors are pieces of rock from space that burn up in our atmosphere. Meteor showers happen when the Earth passes through a large amount of space material during its orbit around the sun. However, thousands of meteors fall during a meteor storm. Some of them may briefly shine brighter than any star in the sky.

(2) In most years, it is not unusual. Leonid meteors fall at an average rate of only 15 each hour. However, every 33 years an object passes through our solar system that changes the Leonid meteor shower.

(3) Comets leave behind these materials as they orbit the sun. Each year around November 18, the Earth passes through material left behind by a comet called Tempel-Tuttle.

In February of 1998, the Tempel-Tuttle comet returned to the inner solar system. Astronomers have found that the Leonid meteor shower can become very active for about five years after the appearance of that comet.

Astronomers also have discovered that each appearance of the Tempel-Tuttle comet leaves behind a different path of material. (4) Some astronomers believe the Leonids this month may be a meteor storm.

This year, astronomers believe that there will be two periods of heavy meteor activity starting on November 18. At 10 Hours Universal Time, observers in North America should see a large number of meteors.

(5) Observers in East Asia and Western Australia will see it best. Astronomers who have researched the Leonids say the best chance to see a meteor storm may be this year and next year.

A.This discovery has permitted astronomers to know when the Leonid meteor shower may be most intense

B. Another period of meteor activity should happen at about 18 Hours Universal Time

C. Leonid meteors shower happens every year

D. The Leonid meteor shower happens every November

E. The event is more than a meteor shower

F. A comet is a large body of gas, ice and rock

正确答案:EDFAB

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