Moon and Company

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The crescent Moon, the planet Venus, and the star Antares stage a beautiful encounter before dawn tomorrow. Look toward the southeast beginning a couple of hours before sunrise. Venus is the "morning star" to the left of the Moon, with orange Antares to the Moon's lower left.

In the late 19th century, a Czech astronomer became famous for an observation of Venus -- not because it was correct, but because it was so wrong.

Venus sometimes appears to us as a bright crescent, just as the Moon does. Carl Zenger observed Venus as a crescent in 1876. He was surprised to find that the inner curve of the crescent seemed jagged and irregular.

In the case of the Moon, this effect is caused by mountains projecting from the dark side of the lunar disk into sunlight. So Zenger concluded that Venus must have mountains, too. In fact, they'd have to be enormously tall to be visible from Earth. To Zenger, tall, bright mountaintops equaled cold mountaintops. In other words, they must be snow-capped!

Modern space probes reveal mountains on Venus -- and some of them are pretty big. But Zenger's lofty peaks were an illusion. Venus is completely encircled by clouds, so we can't actually see the surface at all. Moreover, we now know that Venus is the hottest planet in the solar system, so it's far from icy -- not a place to find snow-capped mountains. Zenger was as wrong as he could be -- famously wrong.

More about this morning lineup tomorrow.

Script by Tom Hockey, Copyright 2007

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