Venus and Regulus

StarDate: September 19, 2009

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The lion will have a double heart tomorrow morning, as the planet Venus cozies up to his "regular" heart, the star Regulus. They're low in the east at first light. Venus is the brilliant "morning star," with fainter Regulus just to its right.

Based on their looks, you might guess that Venus is the more impressive member of the duo -- but you'd be wrong. Venus looks more impressive only because it's much closer to us than Regulus is.

Venus is around 140 million miles away right now. It's on the far side of the Sun, and will pass behind the Sun in a few months. The planet shines so brightly because even at that distance it's a fairly close neighbor, and because it's completely blanketed by bright clouds.

Regulus, on the other hand, is almost 80 light-years away -- more than three million times farther than Venus is. At that distance, the light we see from Regulus tonight left the star around the year 1930.

Since Regulus is so much farther than Venus is, it's also much brighter. Instead of reflecting light, as Venus does, Regulus produces its own light, through the same process that powers the Sun. Yet Regulus is brighter even than the Sun. So if it took Venus's place in our sky, it would look almost a hundred times brighter than the Sun -- and about a hundred billion times brighter than Venus.

So while Venus may out show Regulus in our sky, it's no match for the lion's strong heart.

Tomorrow: a ghostly morning glow.

Script by Damond Benningfield, Copyright 2009

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