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In the Balance

June 29, 2012

The Moon just slips past the claws of the scorpion tonight. They’re represented by two fairly bright stars that are above the Moon at nightfall.

Today, the stars are part of Libra, the balance scales. The name dates to a time when the Sun appeared against those stars at the autumnal equinox, when day and night are of equal length — a time of “balance” in the heavens.

Yet the stars bear names that pre-date Libra by thousands of years: Zubenelgenubi and Zubeneschamali — the southern and northern claws. They were originally part of Scorpius, the scorpion, which is next door to Libra.

Zubenelgenubi stands a little to the upper right of the Moon this evening. Look carefully and you’ll see two stars, not one. The stars probably are bound together by their mutual gravitational pull, even though they’re a long way apart — about 200 times the distance from the Sun to the solar system’s most distant planet.

Zubeneschamali is farther to the upper left of the Moon. It shows only one star, but it’s an impressive one. It’s bigger and brighter than the Sun, and thousands of degrees hotter. Such hot stars shine white or blue-white. But many skywatchers say the star looks green. There’s no way for a star to shine that color, though, so it’s probably just an optical illusion — a trick played by the stars.

The Moon will slide down close to the heart of the modern-day scorpion tomorrow night — and we’ll have more about that on our next program.


Script by Damond Benningfield, Copyright 2012


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