You are here

Vanishing Lights

April 25, 2012

Some of the brightest lights in the night sky line up to the left and lower left of the crescent Moon this evening. They’re all known as denizens of the winter sky. Now that we’re deep into spring, they’re all getting ready to vanish from view.

The constellation Orion is fairly close to the lower left of the Moon. Look for the hunter’s “belt” -- three fairly bright stars that line up parallel to the horizon.

Orion’s brightest stars are above and below the belt -- orange Betelgeuse above, and blue-white Rigel below.

To the left of Orion is the brightest star of the night sky, Sirius. It’s also known as the “Dog Star” because it’s the leading light of Canis Major, the big dog. And the brightest star of the little dog, Procyon, is high above Sirius.

As Earth goes around the Sun, the viewing angle to the stars changes a little bit from night to night. As a result, the stars all rise and set four minutes earlier each night. So over the coming weeks, all of these stars will be a little lower in the sky as night falls. By a month from now, all but Procyon will have vanished in the twilight.

And they’ll stay out of sight for a while, too. The stars of Orion will peek into view in the dawn sky in July, with Sirius following in early August. From most of the United States, Procyon, which disappears from the evening sky long after Sirius does, will actually return to view before Sirius does -- once again leading the Dog Star into the night sky.


Script by Damond Benningfield, Copyright 2012


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.