Weekly astronomy blog for the week ending May 26, 2012
The Crow
A small constellation in the southern skies on May evenings is either a crow or a raven. Corvus has a few named stars and sits near Hydra (a water snake or sea monster) and Crater (a bowl). All three are part of the legend of Corvus.
To the Greeks, Corvus was a bird that served Apollo. Apollo sent him to fetch some spring water. Along the way, the bird saw a luscious fig. He wanted to eat the fig but it wasn’t ripe yet. So he sat by it to wait for it. Finally, the bird got the fig but he would have to explain to Apollo what took him so long. He returned to his master with the cup of water and the water snake in his claws. The bird said the snake had attacked him and caused him to be so late. Apollo knew better and punished the bird by putting him in the night sky with the water cup nearby but the snake nearby too. The bird can’t get to the water for fear of the snake. The Greeks used this story to explain why the crow doesn’t carry water to its own young.
Another story is that Apollo had an affair with Coronis, the daughter of a king. Apollo became suspicious that Coronis was having an affair with someone else and sent a bird with silver feathers to spy on her. When the bird returned and reported to Apollo that Coronis was indeed with someone else, he took his anger out on his feathered messenger. Apollo sent the bird to Hades and turned his feathers black. One may wonder if the Greeks used the story to explain bosses who get mad when their employees do exactly what they were told to do.
One of the stars in Corvus is named Alchiba, which is Arabic for tent. In some lore, the Arabs saw the whole 
constellation as a tent. But the raven link wasn’t unknown to them. Gienah is Arabic for wing. And Algorbab is specifically the raven’s wing in Arabic. Another star is called Minkar. The origin of that name isn’t known.
Alchiba is 48 light years away. Despite being the alpha star of Corvus, it’s not the brightest in the constellation. It’s at fourth magnitude and is not visible to the naked eye in heavily light polluted skies.
The brightest star in Corvus is actually Gienah. It’s third magnitude and is 165 light years away.
Algorab is 88 light years away and is actually two stars. Look at them in a telescope and you’ll see a yellow-orange dot and a purplish one. The purplish dot is Algorab-A. The other one, Algorab-B, is smaller. Algorab-B orbits Algorab-A in some 9,400 years.
Corvus crosses the southern sky for northern hemisphere observers. On May evenings, it’s in the south when the sun sets. From about 20° south, the constellation goes overhead. It’s to the north from places farther in the southern hemisphere. If you need pointers to find it, look for Spica, the brightest star in Virgo. Saturn is somewhat close to it right now. Look a little southwest of them. If you’re not sure you’ve found Corvus, a slightly gibbous moon will be north of it on May 30th. The moon will be just south of Spica the next night.
Enjoy the view of Corvus. ¡SkyCaramba!
http://stars.astro.illinois.edu/sow/alchiba.html