Rare Blue Supermoon Appears in Wednesday Night Sk

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.

tips

confluence 汇合；合并(con- 一起；flu- 流)

elapse 逝去（时间）