You are here

Moon and Companions

June 10, 2011

The Moon and a couple of prominent companions form a bright triangle this evening. Spica, the brightest star of the constellation Virgo, is to the left or upper left of the Moon as night falls, with the planet Saturn farther to the upper right of the Moon.

If you look closely, you'll see that Saturn looks like a double point of light. That's not a case of double vision -- there really are two objects there. Saturn is the brighter one. The other is another star of Virgo, known as Gamma Virginis or Porrima -- the name of a Roman goddess of the future.

And Porrima itself is also two points of light, although lately it's been hard to separate them.

The star is a binary -- two stars locked in a mutual orbit around each other. They're so far away, though, that you need a telescope to see them as individual stars.

The distance between the stars varies by billions of miles. They were closest together about six years ago -- so close that it was hard to see them as two separate stars. They're starting to move away from each other again, but it's a slow process -- they won't reach their greatest separation for decades. But as they move apart, it'll get easier to see Porrima as two stars, not one.

For now, look for Porrima huddling about a degree from the planet Saturn. In fact, they're at their point of closest approach right now. After tonight, Saturn will start to move eastward -- leaving Porrima to face its future alone.


Script by Damond Benningfield, Copyright 2011


Get Premium Audio

Listen to today's episode of StarDate on the web the same day it airs in high-quality streaming audio without any extra ads or announcements. Choose a $8 one-month pass, or listen every day for a year for just $30.