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You might think that astronomers would know just about all there is to know about one of the biggest, brightest stars in our region of the galaxy. That's not quite the case, though. The star still presents a lot of mysteries.
Deneb is the brightest star of Cygnus, the swan. It's high in the eastern sky at nightfall, at the northernmost point of the wide Summer Triangle.
Astronomers do know quite a bit about Deneb. They know that it's around 15 times as massive as the Sun, and more than a hundred times wider. They know that it's hotter than the Sun, and that it pulses in and out a bit, but in an odd way -- like a heart in which each chamber beats to its own rhythm. And they know that's it's a good distance off, although the exact distance is uncertain.
But there are a lot of things that astronomers don't know about Deneb.
They don't know exactly what's happening in its core, for example. They're pretty sure that it's converted its original hydrogen fuel to helium, but they don't know if it's started to burn the helium yet.
They also aren't sure what's around the core. It could be a thin layer in which a gas made of iron atoms rises and falls like the boiling water in a tea kettle.
And they're not even sure how fast Deneb turns. Most stars of its class rotate slowly, but there's some evidence that Deneb spins a lot faster.
In a way, the questions highlight how modern astronomy works; we'll explain how on our next program.
Script by Damond Benningfield, Copyright 2011