Altair

We’ve seen details on the surfaces of only a few stars other than the Sun. Stars are just so far away that most of them look like nothing more than pinpoints of light, even to the biggest telescopes. And most of the ones where we have seen details are either giants or supergiants.

One exception is Altair, one of the members of the bright Summer Triangle. It’s high in the south as darkness falls, and drops down the western sky during the night.

Altair is in the prime of life. It’s a couple of times wider and heavier than the Sun, though, so it’s hotter and brighter than the Sun.

Altair is only 17 light-years away. By astronomical standards, that’s just down the block. That’s allowed astronomers to measure its size and shape, and to get a rough view of its surface.

They observed Altair with a set of small telescopes. They were linked through a technique known as interferometry. The combined telescopes see more detail than a single giant telescope could reveal.

The interferometer confirmed estimates of the star’s size made with other techniques. And they showed that the star is squished — it’s about 20 percent thicker through the equator than through the poles. That’s because the star rotates much faster than the Sun does, which pushes gas at the equator outward.

Finally, the technique produced rough images of Altair, showing big areas of light and dark on its surface — details that have been seen on few other stars.

Tomorrow: Stalking the full Moon.

Script by Damond Benningfield