Mars, Saturn, and Regulus

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The heart of the lion is pretty strong all on its own. But it looks even stronger the next few nights because it's flanked by two strong companions.

The lion's heart is Regulus, the brightest star of the constellation Leo. And its companions are the planets Mars and Saturn. The threesome forms a short line in the west as darkness falls. Saturn is at the top of the line, with Regulus and then Mars to its lower right. Saturn is about twice as bright as the other two.

The lineup is possible because all three bodies lie along the ecliptic -- the Sun's path across the sky.

Regulus is one of a handful of bright stars on the ecliptic. Because the Sun passed close to each of them during the year, they held special significance in the ancient world. In Persia, Regulus and three others were considered the "guardians of heaven." Each one ruled over a quadrant of the night sky.

The planets all orbit the Sun in roughly the same plane, which is outlined by the ecliptic. But they move along the ecliptic during the year -- they don't keep the same spot as the true stars do. So over time, they pass by each of the ecliptic's bright stars.

Mars completes one circle through the ecliptic in about two years, so it'll come back to Regulus in the spring and summer of 2010. But Saturn takes almost three decades to complete the circle. It won't return to bolster the heart of the lion until 2036.

More about this bright lineup tomorrow.

Script by Damond Benningfield, Copyright 2008

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