Jimmy Westlake: Stalking the unicorn
February 14, 2012
Steamboat Springs — The late-winter sky is sparkling with bright stars. Wintertime's showpiece, Orion the Hunter, boasts two luminaries, Betelgeuse at his shoulder and Rigel at his foot. His two canine companions each show off a bright star, Sirius and Procyon. The Gemini Twins have Castor and Pollux; Auriga the Charioteer holds the golden star Capella in his arms; ruddy Aldebaran marks the glaring eye of Taurus the Bull; and icy-blue Regulus marks the heart of Leo the Lion.
If you were a constellation made of very faint stars and didn't want to draw attention to yourself, there couldn't be a better spot for you to hide than among the brilliant stars of winter.
That's exactly where we look to find the faint constellation of Monoceros, representing the shy, reclusive creature of legend known as the unicorn. Modern depictions of this unusual beast resemble a beautiful white horse, except for the single prominent horn that protrudes from its forehead. Originally, however, the Unicorn was a hybrid animal with the body of a horse, the cleft hooves of a stag, the tail of a lion and, again, the single horn. Unicorns were considered magical creatures. The lucky person who could capture a unicorn and cut off its horn would be protected from harm.
The celestial unicorn is a relative newcomer to the sky. It doesn't date back to the time of the Babylonians or ancient Greeks, as many of our constellations do, but it seems to have appeared from out of nowhere on a star chart published in 1624 by Jakob Bartsch, the son-in-law of famed astronomer Johannes Kepler.
Monoceros is corralled in the triangular patch of sky staked out by the three bright winter stars Sirius, Betelgeuse and Procyon, an asterism known as the Winter Triangle. At first glance, you might think that there is nothing at all visible within this triangle, but look more closely. The faint stars forming the head and body of the unicorn are just at the limit of visibility. Even Orion, the great hunter lurking nearby, seems oblivious to the mythical beast sneaking up behind him.
If you own a pair of binoculars, you can spot the famous Rosette Nebula and its associated star cluster NGC 2244 about one-third of the way between Betelgeuse and Procyon. This vast cloud of hydrogen gas is forced to glow by the ultraviolet light emitted from the hot stars in its center. It is somewhat fainter and more difficult to see than its more famous neighbor to the west, the Great Orion Nebula, but well worth the effort.
Look for Monoceros the Unicorn on a clear moonless night because the slightest amount of moonlight provides perfect camouflage for this elusive creature.
Jimmy Westlake teaches astronomy and physics at Colorado Mountain College's Alpine Campus. Check out Jimmy's astrophotography website at http://www.jwestlake.com.