Moon, Regulus, and Saturn

StarDate: January 13, 2009

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The Moon glides between the star Regulus and the planet Saturn tonight. All three are in good view in the east by around 11 o'clock, and climb high across the south later on.

The light from all three of these bodies strikes your eyes at the same time. But the light followed different paths to get there.

All the light came from stars.

Regulus is a star itself. Its surface is quite hot, so Regulus shines almost pure white. The light from Regulus takes more than three-quarters of a century to get here. So the light you see from Regulus tonight actually left the star near the start of the Great Depression.

The Moon and Saturn don't produce any light of their own. We see them only because they reflect the light from another star: the Sun.

Saturn's atmosphere absorbs blue wavelengths of light and reflects the yellows and reds, so the planet looks like a golden star. Right now, it takes about two and a half hours for light to leave the Sun, bounce off of Saturn, and reach Earth.

The Moon is dark gray. But it's so big in our sky that it's quite bright, so the unaided eye tends to see it as white with splotches of gray. Sunlight takes about eight minutes to reach the Moon, but only a bit more than a second to bounce over to Earth.

Regulus is just a little to the upper left of the Moon as they rise late this evening. Saturn is farther to the lower left of the Moon. We'll have more about Saturn and the Moon tomorrow.

Script by Damond Benningfield, Copyright 2005, 2008

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

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