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Looking Up: Happy Halloween!

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Blue Straggler Stars in Globular Cluster M53
Credit ESA/Hubble, NASA
Blue Straggler Stars in Globular Cluster M53

On this Halloween edition of Looking Up we hear about a vampire star.  

The leaves are mostly off the trees, pumpkins abound, and the spooky holiday of Halloween has arrived. Tonight the streets will be filled with all manner of ghosts and goblins, and probably quite a few Harry Potter’s. But if Count Dracula arrives at your door, you might let the little one know about a far bigger vampire -- the vampire star SS Leporis! 

The constellation Lepus, the hare, lies below Orion, and to the east of Canis Major, forever running across the sky, being chased by Orion’s hunting dog. I’m serious. Sorry, star pun. But hidden within Lepus is a star that appears to be staying young by sucking the life force of another star. Cue the spooky Halloween music!

Like a cosmic Dorian Gray, SS Leporis is a member of class of stars known as Blue Stragglers. These are stars that are far older than their spectral evidence would suggest. They seem to be staying young somehow. Astronomers believe that Blue Stragglers are cosmic vampires. They stay young by sucking matter from a nearby star. These binary star systems are freaky and scary places. If you could observe SS Leporis up close, you would see a smaller star slowly and relentlessly, sucking material from its larger neighbor, and onto its own surface.

These two stars orbit each other in roughly 260 days, and are separated from each other by only a little more distance than the Earth is from the Sun, but the cooler, victim star is so big that it surface extends a quarter of the way across the gap. The smaller, hotter, vampire star pulls material onto itself. Astronomers estimate it is already sucked the blood, I mean pulled off up to one half of the big star’s mass. We don’t know exactly how this works. It’s possible that the vampire star is simply absorbing the material blown off of the larger star. But some astronomers think it may be actively sucking material. You might say the debate is neck and neck!

If you’d like to take a closer look at Lepus, 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! 

This is Hal Bidlack for the Colorado Springs Astronomical Society, telling you to keep looking up, Southern Colorado!