Altair

Altair is a close neighbor – just 16.7 light-years away. Only about 50 star systems are closer. And it’s bigger and brighter than the Sun, so it’s easy to study. Even so, not even the largest individual telescopes can see it as more than a bright dot. Yet astronomers have managed to take a fairly detailed picture of it.

They’ve done so with a technique known as interferometry. It combines the views from several fairly small telescopes that are linked together. That reveals as much detail as a single giant telescope. Just how much detail depends on the number and size of the telescopes, and how far apart they’re spaced. The setup doesn’t necessarily see fainter stars and galaxies, but it does see the universe with greater clarity.

With conventional telescopes, astronomers had found that Altair spins in a hurry – once every eight hours, versus about 25 days for the Sun. That suggested the star was flattened. They measured that flattening with an interferometer; the star is about 25 percent wider through the equator than through the poles.

A few years later, they confirmed that it’s cooler and darker around the equator. And in 2006, they even took a picture of Altair – the first detailed image of any Sun-like star.

Altair is high in the southeast at nightfall, at the lower right corner of the bright Summer Triangle. We’ll talk about another member of the triangle tomorrow.

Script by Damond Benningfield