More Moon, Regulus, and Saturn

StarDate: June 26, 2009

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The Moon has a couple of bright companions this evening: Regulus, the star that marks the "heart" of Leo, the lion, and the planet Saturn. They're all in the west as darkness falls. Regulus is a bit to the right of the Moon, with brighter Saturn a little farther to the Moon's upper left.

As early as six millennia ago, the people of ancient Persia saw Regulus and three other bright stars as a celestial ruling class -- the Four Guardians of Heaven. Regulus was the most important of the bunch.

The stars were significant because they first appeared just before sunrise at important times of the year. Regulus, for example, popped into view at the time of the summer solstice.

But summer arrived just a few days ago, and Regulus is nowhere near the Sun. In fact, the Sun won't get close to Regulus for another couple of months.

That's because of an effect called precession, which causes the seasons to move with respect to the stars.

Earth wobbles on its axis like a spinning top. As a result, the axis points to different positions on the sky over time, so the stars appear near the Sun at different times of the year. It takes 26,000 years for Earth to make one full "wobble" and the axis to complete a full cycle through the stars. So Regulus will once again mark the summer solstice in another 20,000 years.

For now, though, look for Regulus in the evening skies of summer -- tonight, near the Moon and the planet Saturn.

Script by Damond Benningfield, Copyright 2009

For more skywatching tips, astronomy news, and much more, read StarDate magazine.

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