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A young eagle soars across the sky on summer nights. Right now, it’s low in the east at nightfall, due south in the wee hours of the morning, and high in the southwest at dawn. And it’s easy to spot — it’s the 12th-brightest star in the night sky.

Altair represents the breast of the constellation known as the eagle. The name “Altair,” in fact, means “the flying eagle.”

According to current understanding, it’s a young eagle — barely more than an eaglet. It’s about a hundred million years old, compared to four and a half billion years for the Sun. And it’s just entering stellar adulthood — what’s known as the “main sequence.” That means it’s fully formed, and it generates energy through nuclear fusion in its core — it “fuses” together hydrogen atoms to make helium.

One of the hallmarks of young stars is that they spin in a hurry — a result of the collapse of the cloud of gas and dust that gave them birth. And Altair is no exception. It turns on its axis once every eight hours, compared to almost a month for the Sun. That’s about 75 percent of the speed needed to make Altair fly apart.

The whirligig action also flattens the star, so it’s almost 25 percent fatter through the equator than through the poles — an effect clearly seen in images of Altair — a young, bright eagle flying through summer nights.

Altair has a close attendant, and we’ll talk about that star tomorrow.

Script by Damond Benningfield

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