Looking Up: Right Where You Belong

Dec 10, 2018

"Aries and Musca Borealis", plate 16 in Urania's Mirror, a set of celestial cards accompanied by A familiar treatise on astronomy ... by Jehoshaphat Aspin. London.
Credit Sidney Hall. Restoration by Adam Cuerden / Wikimedia Commons

This week on Looking Up Hal invites us to 'check out' a star by the name of Sheratan, conveniently located in the Colorado night sky near you.

If you are ever wondering where to spend a night looking at the Colorado night sky, may I suggest stopping by the Sheratan? And by Sheratan, I mean the very cool star Sheratan, high in our night sky right now.

Scientifically known as Beta Arietis, the second brightest star in Aries, Sheratan looks very ordinary, until you dig a bit deeper. First off, it’s name, Sheratan, means, well we don’t really know. Originally, this name referred to two stars in Aries, but now just the one.

Sheratan is very special because of what it hides – a tiny companion star only 5% as bright. But that alone isn’t too special, as there are lots and lots of double stars out there. But what makes Sheratan really freaky is that this companion star has one of the most elliptical – or squished – orbits we’ve found, with an eccentricity of .88. That means that when the companion star is closest to Sheratan, it’s only a bit over 7 million miles from Sheratan. But at it’s farthest away point in the orbit, the companion is over 111 million miles away. Pretty strange, eh? But it gets weirder – in a few billion years, the stars will switch brightness, as Sheratan uses up its fuel, and the baby companion starts to outshine its big brother. I’ve seen that in Earth families. 

Arrow points to Sheratan (Beta Arietis)
Credit Torsten Bronger / wikimedia - This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

If you’d like to take a closer look Sheratan, 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.