Moon and Companions

StarDate: April 4, 2009

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A couple of bright lights trail the waxing gibbous Moon across the sky tonight. One of them is a star, while the other is a planet.

As darkness falls, Regulus and Saturn line up to the lower left of the Moon. Regulus is closer to the Moon, while Saturn is a little brighter.

Regulus is the brightest star of Leo, the lion. Saturn is a planet -- the second-largest in the solar system.

Like all the planets, as Saturn orbits the Sun it loops through the background of stars as seen from Earth. It takes about 30 years to complete a single loop, so it spends anywhere from a few weeks to a few years inside the borders of each of the 13 constellations along its path.

Leo is one of the widest of these constellations, so Saturn lingers inside its borders for a long time. This time, for example, it entered Leo in late summer of 2006, and won't leave the lion behind until late summer of this year. After that, it'll head into the neighboring constellation Virgo for another long visit.

Saturn's path through the stars isn't a steady one, though. The planet periodically stops its normal eastward motion and moves backwards for a while -- in fact, it's doing that right now. It doesn't really double back on itself, though. It only appears to change direction as Earth passes by the planet each year.

Keep an eye on Saturn as it completes its sojourn across Leo over the next few months. It won't return to the lion for more than a quarter of a century.

Script by Damond Benningfield, Copyright 2009

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