詞匯?

1.????? confluence 匯合，交匯

2.????? occur 發(fā)生，出現(xiàn)

3.????? decade 十年

4.????? elapse 時(shí)間消逝

5.????? average 平均數(shù)，平均的，普通的

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Rare Blue Supermoon Appears in Night Sky

A rare blue supermoon appeared in the sky Wednesday night. A blue supermoon, or super blue moon, is the confluence of two events: A supermoon--when a full moon occurs within a day of the moon's closest point of orbit to Earth--and a blue moon, when it's the second full moon in a single month.

According to the National Aeronautics and Space Administration, as many as two decades can elapse between blue supermoons, but about 10 years is the average. The next blue supermoons are expected in 2037, in January and again in March of that year, NASA said.

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