Puppis

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Sailors head for the water on gusty spring days -- ready to unfurl the canvas and glide across the waves. And after dark, the sailing continues in the night sky. The Argo sails low across the south -- the fabled ship that carried Jason and the Argonauts.

Originally, the Argo was a single giant constellation. But in 1763, astronomer Nicolas Louis de Lacaille split the ship into three smaller pieces: Carina, the keel; Vela, the sail, and Puppis, the poop deck or stern. Carina is below the horizon from most of the U.S., but Vela and Puppis are in the south at nightfall, and cruise westward during the evening.

Puppis is the bigger of the two. It stretches about a third of the way up the southern sky. It includes several modestly bright stars, although none of them are all that impressive to look at.

But when you learn more about them, a few of its stars are quite impressive. One of them spans about 250 million miles; if it were in our own solar system, it would extend almost all the way out to Mars.

Puppis also is home to the hottest star that's visible to the unaided eye -- a blue supergiant known as Zeta Puppis. Its surface is more than 60,000 degrees hotter than the Sun. We'll have more about the star tomorrow.

To find Puppis, look to the left and lower left of Sirius, the brightest star in the night sky, which is in the southwest in early evening. The poop deck forms a tall, skinny wedge rising from the southern horizon.

Script by Damond Benningfield, Copyright 2008

For more skywatching tips, astronomy news, and much more, read StarDate magazine.