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A New Cycle

May 24, 2013

A new cycle of eclipses begins tonight. Unfortunately, though, this one barely qualifies as an eclipse at all. The full Moon basically just dips its toe in Earth’s faint outer shadow, the penumbra. That shadow will cover just about one percent of the lunar disk. And the shadow is so faint that no one will notice the difference.

Eclipses come in groups. Each group is known as a Saros. The circumstances for each eclipse in the group are similar — the Moon is about the same distance from Earth, for example, and they occur at the same time of year.

Each Saros begins with a bare penumbral eclipse, like the one tonight. With each succeeding eclipse, though, the Moon dips a little deeper into Earth’s shadow. By the middle of the cycle, the eclipses are total, with the Moon completely immersed in the shadow. After that, the Moon moves away from the center of the shadow, and the cycle ends with another grazing penumbral eclipse — but this time with the Moon at the opposite side of the shadow.

Tonight’s eclipse is the first of Saros 150. It will consist of 71 eclipses in all, with each one coming a little more than 18 years after the previous one. So Saros 150 will last 1262 years — with its final eclipse on June 30th, 3275.

While tonight’s eclipse isn’t much to look at, there is a consolation. The star Antares, the bright orange heart of the scorpion, rises just below the Moon, and stays close to the Moon throughout the night.


Script by Damond Benningfield, Copyright 2013

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