Sunday, August 30, 2009

Constellations, Sagittarius and Scorpius

Sagittarius, the Archer Sagittarius, the archer, whose brightest stars form the shape of a teapot slides low across the southern sky of summer. Sagittarius has drawn his bow, and his arrow is pointing at Antares, the bright red heart of Scorpius, the scorpion. The archer is avenging Orion, who was slain by the scorpion's sting.

The constellation Sagittarius is one of the most interesting regions of the sky. The center of our Milky Way galaxy lies inside Sagittarius, about 26,000 light years away. The constellation also contains several globular clusters tightly packed collections of hundreds of thousands of stars.

Antares is a yellow-orange supergiant star 600 light-years away in the constellation Scorpius.
The star Antares marks the "heart" of Scorpius, the scorpion. It is the brightest star in Scorpius. It's the most difficult to see in the early twilight, but as the sky gets darker, it stands out more. Antares also stands out because of its color. While most of the stars show little or no color, Antares is a vivid orange. That's the result of its surface temperature, which is thousands of degrees cooler than the Sun.

But Antares is a supergiant star, one of the biggest and most massive in our part of the galaxy, so its interior is millions of degrees hotter than the Sun's interior. Like most supergiants, Antares is likely to end its life with a bang, it'll explode as a supernova. That could happen anytime within the next few million years, or as early as tonight.

Scorpius, the Scorpion Three bright stars form the "head" of Scorpius, the celestial scorpion, while its tail curves away below it in the southern sky of summer.

The brightest star in Scorpius is Antares, which is in the middle of the scorpion's curving body. This brilliant red star is one of the behemoths of our stellar neighborhood. If you placed it at the center of our own solar system, it would swallow Mercury, Venus, Earth, and Mars, and almost reach Jupiter.