We close out 2010 with a look at the constellation Monoceros. This dim constellation, which represents a celestial unicorn, holds no bright stars and is often overlooked for brighter Orion and Gemini and Canis Major. But don’t pass this constellation by. It holds more interesting deep-sky objects than Orion, and gives you many pleasurable moments of stargazing in the waning days of the year.
Monoceros occupies the barren gulf of sky bordered by Orion to the west, Gemini to the north, Canis Major to the south and Hydra to the east. Since it lies on the celestial equator, it’s visible to observers in both hemispheres. Seeing the outline of a unicorn in this dim patch of stars is nearly as challenging as seeing a real unicorn. If you’re in the city, you’ll find it hard to spot any stars at all. The brightest star in Monoceros is magnitude 3.9, and only four stars come close to 4th magnitude.
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A map showing the constellation Monoceros, east of Orion. The massive object called Plaskett’s Star is highlighted by a circular marker at center-left.
You might think a constellation that sits near to Orion and takes its name from a unicorn has a long and rich history dating to classical times. But this is not so. Monoceros is a fairly new constellation, and the Greeks had no legends of unicorns. The constellation was first included on a star chart by Petrus Plancius in the early 1600’s, and formalized by Jakob Bartsch in his star charts later in the 17th century.
While Monoceros offers little for the unaided eye, it presents a number of fascinating sights for those armed with binoculars or a telescope. We’ve looked at the splendid multiple star beta Monocerotis already… a stirring sight in a small telescope.
Monoceros also holds Plaskett’s Star, one of the most massive binary stars in the sky, with a combined mass of more than 100x our own Sun (see image above). The star was named after the Canadian astronomer John Stanley Plaskett, who determined the binary nature of this monstrous star.
We leave this constellation’s most accessible sights for the next few installments.
For now, simply acquaint yourself with Monoceros. Wander outside to see if you can find its brighter stars, including the multiple star beta Mon. Next time, we’ll look a lovely star cluster in Monoceros that’s surrounded by a “Christmas wreath” of glowing gas and dust.
But for today, that’s it…