Looking Up: Knee High To A Queen

Oct 21, 2019

This file is licensed under the Creative Commons Attribution-Share Alike 2.0 Generic license.
Credit chaouki / Flickr: cassiopeia / wikipedia.org

This week on Looking Up Hal kneels at the throne of Cassiopeia in order to pay homage to the star Ruchbah.

Today I’d like to tell you about an interesting star, high in the Colorado night sky right now, the star Ruchbah. Ruchbah is the 4th brightest star in the northern constellation of Cassiopeia. In Arabic, Ruchbah means “the knee” which makes sense, given that Cassiopeia is supposed to be a queen sitting on her throne.

I admit, to me Ruchbah sounds like someone yelling in Klingon, but the star behind the name is quite a bit hotter than our Sun and is about 63 time brighter. Ruchbah is located almost exactly 100 ly from Earth. Really good telescopes can just make Ruchbah, which is about 4 times bigger across than our Sun, out as a disk, as opposed to a single point of light, which is pretty amazing. Ruchbah is a giant star, or maybe a sub-giant star, but in either case, it’s in trouble.

It seems this star, only 600 million years old, is already dying. Our Sun is about 4.5 billion years old, meaning that Ruchbah is only about 13% as old as the Sun, but yet is already heading toward becoming a giant star in about 10 M years, followed by, well, things don’t end well for such stars. But for the moment, we have a knee to look at and a throne to admire, and so I urge you to take a look at Ruchbah before it is too late! 

This image is available from the United States Library of Congress's Prints and Photographs division under the digital ID cph.3g10052. "Cassiopeia", plate 3 in Urania's Mirror, a set of celestial cards accompanied by A familiar treatise on astronomy ... by Jehoshaphat Aspin
Credit Sidney Hall [Public domain]; Restoration by Adam Cuerden / wikimedia commons

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