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Moon and Regulus

December 15, 2011

The Moon has a bright companion as it rises late this evening: Regulus, the brightest star of Leo, the lion. It’s to the upper left of the Moon as they rise, and to the upper right at first light tomorrow.

Near the middle of the gibbous Moon, look for a small, bright dot amid the dark volcanic plains — the crater Copernicus. It’s visible to the unaided eye, although binoculars will enhance the view.

The crater formed a billion years ago, when a large asteroid slammed into the lunar surface. The impact blasted out billions of tons of rock. Some of the material splashed back onto the lunar surface, forming small craters and “rays” of bright-colored rocks around Copernicus. But some of the material was going so fast that it escaped the Moon entirely. In fact, some of it probably fell right here on Earth.

The impact also created a shockwave that pushed some of the rock to the sides, building a rim around the crater. Some of the shockwave’s energy rebounded, pushing up a mile-high mountain at the crater’s center.

When the fireworks were over, the Moon was left with a round scar that’s close to 60 miles across and two miles deep. Its flat floor is wide enough to hold a large city, and its rim consists of sculpted layers, like benches around an amphitheater built for giants.

Even though it’s ancient by human standards, Copernicus is quite young for a lunar crater, so its appearance is sharp and fresh — making it easy to see on the jumbled lunar surface.


Script by Damond Benningfield, Copyright 2011


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