Constellation

Constellations

 

Aquila shines on the front wings through the glowing band of the Milky Way. Look at it high in the south in late summer.Aquila, EagleAquila's brightest star is Altair, the "eagle", a white star about 17 light years from Earth. Altair is the southernmost point of the pattern of three bright stars known as the Summer Triangle. (Deneb, in the planetarium Cygnus, forms the northeastern point of the triangle. Vega is in Lyra, northwest. Altair is nice and bright and easy to find right until the beginning of winter.)Altair is nearly twice that of the Sun, so it would only equal 10 billion of the Sun versus two billion years. Despite its size, Altair appears to turn its axis once every 10 hours, compared to about four weeks for the Sun. One of the effects of Altair's high-speed rotation is that its gas moves outward from the equator, making the star appear flattened - it is about 14 percent wider through the equator than the poles. If Altair rotates about twice as fast, it will now split.The medium bright star Taraz is quite close to Altair. The star is only 100 million years old, compared to 4.6 billion years for the Sun. But it has passed the end of its "normal" lifespan, causing its outer layers to flow in vast proportions.

It is about 100 times the diameter of the Sun, so it is about 2,500 times brighter than the Sun. This makes it easy to see, even if it is about 400 light years away.Aquila's two "tailed" stars are Zeta and Epsilon Aquile. Together, they also have an old Arabic name: Deneb al Okab, "Eagle's Tail." The northern star in the tail is actually a system of three or more stars. Only one of them is enough to see without eyes. It is a type of star known as the red giant. This means that it is in the final stages of life. Its core is getting warmer and denser, while its outer layers are cooling out. The southern star is also a multi-star system. Its brightest star is very early in life. It is larger, heavier and warmer than the Sun, and it rotates about 200 times faster than the Sun, so, like Altair, it moves out at the equator, making it look like a squash beach.The Pioneer 11 spacecraft, which was launched in 1973, is heading to one of the eagle's stars, the Lambda Aquile, which is 125 light years away. Pioneer would pass the star in about four million years. Although the spacecraft is already finished, it carries a message from home: a small plaque with information about the craft and its makers - a greeting to the galaxy from the people who were making Pioneer 11.