Looking Up: Mira Mira In The Night, Now You See Me, Now You Might...

Oct 30, 2017

The Tail of a 'Wonderful' Star
Credit NASA, JPL-Caltech, GALEX, C. Martin (Caltech), M. Seibert(OCIW) / nasa.org

This week on Looking Up Hal has a Halloween themed story in mind.

Well, it’s almost Halloween – a night for strange and spooky stuff and maybe a good ghost story. So how about I tell you the tale of the strange and ghostly star, Mira?

Mira is located in the constellation Cetus, high in the southern Colorado sky on cool Fall nights. And Mira is a sneaky star that seems to be doing an impression of a ghost, because it seems to disappear completely and then reappear – spooky, right?

Mira is what’s known as a long period pulsating variable star. When it was first recorded in 1597 it was a relatively bright star, with a magnitude of 3. Over the next few months, Mira faded from view, causing the astronomers of the day to assume it had been a nova that had burned out. Imagine their surprise when in 1609 a new star seemed to show up in the same place.

With a temperature of only a bit over 3000 F, Mira is one of the coolest stars in the sky. And it varies dramatically in brightness over a roughly 332 day cycle. But even in that cycle, Mira is very strange, in that sometimes it brightens dramatically, over 500 times brighter than it was before, and other times in only brightens a little bit. Mira is very likely a cool Red Giant star, 700 times bigger than our Sun, pulsating as it lives out its final few centuries of life before it collapse into a burned out white dwarf, far small than the Earth. So Happy Halloween and watch out for witches and really strange stars above.

If you’d like to take a closer look at Mira or any of the 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.