Ancient skywatchers gave the constellation Ophiuchus a delicate job. He's the serpent bearer -- a man whose healing powers reminded people of a snake, which "renews" itself every year when it sheds its skin. But those same skywatchers made sure he was well prepared for the job. His left hand is represented by not one star, but two.
Those stars are in good view in the eastern sky at nightfall, a couple of handwidths above the horizon. Neither one is all that bright on its own, but together they make a nice sight. The brighter of the two is known as Yed Prior. The other, Yed Posterior, is just below it.
The names are a bit of early multiculturalism. The word Yed is Arabic for "hand." Prior and Posterior come from Latin, and mean "in front" and "behind."
The two stars have something in common: Both are classified as giants. That means they're late in life. Their cores are undergoing dramatic changes, causing their outer layers to puff up to giant proportions. Both stars are bigger than the Sun. Yed Prior is the larger of the two. If it took the Sun's place, it would extend about two-thirds of the way out to Mercury, the innermost planet. That makes Yed Prior look brighter than Yed Posterior, even though it's more than 60 light-years farther.
Look for the hand of the serpent bearer beginning around nightfall. The rest of Ophiuchus stretches below and to the left of the hand, with the head of the snake to the upper left.
Script by Damond Benningfield, Copyright 2009
For more skywatching tips, astronomy news, and much more, read StarDate magazine.