Orion Disappears

StarDate: April 24, 2009

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With winter more than a month behind us, one of the last reminders of the season is disappearing from the evening sky. It'll move into the morning sky this summer, beginning another year-long trek across the night.

Orion, the hunter, is low in the west as night begins to fall. Start looking for it about a half-hour after sunset, when its two brightest stars will just begin to shine through the twilight. Rigel is quite low in the sky, so you'll need a clear horizon to spot it. Betelgeuse is much higher, so it's a little easier to pick out.

Both of these stars are supergiants -- the largest and most massive of all stars. They're also the brightest, so each star is visible across hundreds of light-years of space -- even through the glow of twilight.

As the sky gets a little darker, several other stars will pop into view. That includes Orion's Belt -- a short line of three fairly bright stars that's parallel to the horizon. The stars that make up the belt are also giants or supergiants. In fact, one of them consists of two giant stars in a single system. These stars are also hundreds of light-years away. And the belt has another distinction: the celestial equator passes just above it. More about that tomorrow.

Within a week or two, Rigel will be so low in the sky that it'll be lost in the Sun's glare. The rest of the hunter will follow over the next few weeks -- taking a break before its return to the morning sky this summer.

Script by Damond Benningfield, Copyright 2009

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