This week on Looking Up we learn that even an old workhorse star like Polaris needs a little time off now and then. We also learn which star will be filling in for Polaris as the "north star".
Have you ever looked up at the stars and wondered which of those thousands upon thousands of visual stars might have planets going around them?
Well, if you’ve looked up at Gamma Cephei, better knows as Alrai, you have. Alrai is a really cool star, high in the Colorado night sky all year round, in the far northern sky, and it’s one of the few stars with planets we can see naked eye. And that positioning is important, because Alrai is interesting for other reasons. But about that planet – it was first detected in 1988 but wasn’t confirmed until 2002, making it one of the first suspected exoplanets. And here’s where it gets weird – Alrai is a double star system. That means that the planet has two suns and a really weird orbit.
And speaking of planets, did you know the Earth wobbles on its axis like a top slowing down? It does, in a roughly 26,000 year cycle. And that’s where Alrai comes back in. From roughly the year 3500 AD and for a few thousand years more, Alrai will replace Polaris as the “north star.” In fact, there are several stars that act as the North Star over that cycle. That’s why, for example, the pyramids in Egypt don’t line up due north any more – they used a different north star back then. So modern pyramid builders, heads up!
If you’d like to take a closer look Alrai, or any of the other wonderful and amazing things in the sky, please visit csastro.org for a link to information on our monthly meetings and our free public star parties.