Moon and Companions III

StarDate: December 2, 2010

You are missing some Flash content that should appear here! Perhaps your browser cannot display it, or maybe it did not initialize correctly.

You are missing some Flash content that should appear here! Perhaps your browser cannot display it, or maybe it did not initialize correctly.



Venus is always a brilliant beacon in Earth's sky. But the planet is especially bright right now -- about 10 times brighter than any other point of light in the night sky. Only the Moon outshines it.

These two bodies are fairly close to each other early tomorrow. They're in the southeast about 45 minutes before sunrise. Venus is the "morning star," above the Moon. A couple of other bright pinpoints are above them: the star Spica and the planet Saturn.

Venus's brightness depends on two things: its phase and its distance from Earth. It's only a crescent right now -- a little thicker than the Moon. But it's also quite close to Earth. That means it looks bigger in our sky than at other times, and it reflects more sunlight in our direction.

Venus shows phases because it's an "inferior" planet -- its orbit is closer to the Sun than Earth's orbit. As a result, the planet passes between Earth and the Sun. When it crosses the line between them, it's "new" -- just as the Moon is new when it crosses between Earth and the Sun.

As Venus moves away from that line, it slowly waxes. Over a period of several months, it moves to the opposite side of the Sun, so sunlight illuminates almost the entire disk. By then, though, Venus is tens of millions of miles farther away, so while it's bright, it's not as bright as it is during its crescent phase.

For now, though, watch the planet at its most brilliant, dominating the pre-dawn sky.

 

Script by Damond Benningfield, Copyright 2010

 

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

The one constant in the Universe: StarDate magazine

FacebookTwitterYouTube

©2014 The University of Texas McDonald Observatory