Sky Watch: The unicorn after dark
Among the stars of the night sky lie constellations that derive from real and imaginary people, animals and objects, but rarely can anyone trace the images they represent. Take, for example, the flying steed known as Pegasus. I defy anyone to look skyward and outline its stars in such a way that they can see a flying horse. And if you can, well, I'm afraid you'll need more help than I can give you.
Years ago, during my internship at the Strasenburgh Planetarium in Rochester, our director was fond of saying that the constellations look no more like their namesakes than the George Washington Bridge looks like the Father of our Country. And, of course, he was absolutely correct.
Another fine example of such a star grouping that's tough to outline is the constellation Monoceros, the unicorn. Monoceros is composed of rather faint and obscure stars, and we often overlook it because it happens to lie within some of the most brilliant celestial real estate. Search for it this week after dark (before the bright moon rises), just to the east of dazzling Orion and between the bright stars Sirius and Procyon.
It's always tough to know where these constellations originate; often their roots are lost in antiquity, but we think that Monoceros may have a bit more modern origin. Some believe that it might have been the sixteenth Century Dutch theologian, cartographer and astronomer Petrus Plancius who invented this constellation, though some think it was actually named "Unicornu" by German astronomer Jakob Bartsch who published Plancius' star maps in 1624.
If you are able to find the constellation in a dark, moonless sky -- which is pretty much the only way this is possible -- you should also be able to see the Milky Way flowing gently southward through it.
Once you find Monoceros, you'll discover it takes quite an imagination to fashion a unicorn out of this star grouping. But it's not so much the constellation that's interesting as what's lurking within. Though they're rather faint, a number of celestial wonders are visible if you have a small telescope.
Monoceros is home to a beautiful triple star system -- three stars which orbit a common center of gravity -- known as Beta Monocerotis. It was the famous astronomer William Herschel who discovered it in 1781, the same year he found the planet Uranus. Herschel found the three stars of Beta Mon to form a triangle that, from our distance of nearly 700 light years, appears not to change over time, and he described it as one of the best triple star systems he'd ever seen.
Also lying within the boundaries of Monoceros is the famous interstellar cloud named the Rosette Nebula that engulfs a star cluster known as NGC 2244. With a backyard telescope, one can sometimes make out some diffuse nebulosity here, but it takes a pretty hefty scope to distinguish its ringed shape.
Even if you don't own a large enough telescope to see these celestial wonders, I hope you'll at least get out to search for the unicorn. It may be the only one you ever see!