The three stars marking Orion’s Belt, Alnilam, Alnitak and Mintaka, are visible high in the southern sky at about 9 p.m. in January. Look at the middle star in Orion’s sword, just below his belt, to find the Great Orion Nebula.
Wednesday, January 12, 2011
Jimmy Westlake's Celestial News column appears Tuesdays in the Steamboat Today.
Find more columns by Westlake here.
Steamboat Springs Anyone who ever has looked up at the starry, winter sky has seen it, though they might not have realized what they were looking at. The three bright stars in a neat little row stand out among the other stars like a neon sign. Some folks mistake this asterism for the Big Dipper. Some call them the Three Marys, and still others refer to them as the Three Wise Men. But officially these three stars mark the belt of Orion, the Hunter. Their ancient names are, from left to right, Alnitak, meaning “the girdle,” Alnilam, meaning the “string of pearls,” and Mintaka, meaning “the belt.”
Three fainter stars below the belt represent Orion’s sword, hanging at his side. When the 18th century French astronomer and comet-hunter Charles Messier aimed his telescope at the middle star in the sword of Orion, he thought he might have discovered a new comet. The object certainly had the fuzzy, cloud-like appearance of a comet. To Messier’s dismay, however, the object turned out not to be a comet. He had, instead, made an independent discovery of what now is known as the Great Orion Nebula. It became the 42nd entry in Messier’s now-famous catalogue of comet look-alikes and is therefore known as Messier 42, or just M42.
M42 has become one of the most photographed and carefully studied deep sky objects in the heavens. It is the closest and best example of an ionized cloud of hydrogen gas in space called a diffuse nebula. Any small telescope or even ordinary binoculars will reveal the fuzzy appearance of M42. It resembles a cluster of streetlights seen through a thick fog. The source of the light illuminating the nebula is a quartet of four very hot, luminous stars collectively called the Trapezium. NASA’s Hubble Space Telescope and Spitzer Space Telescope have helped unravel the mysteries of this colorful cloud of gas. The Great Orion Nebula is a stellar nursery where thousands of new stars and planetary systems are condensing from the interstellar gas. A few million years from now, a cluster of new stars will there.
No optical aid is required to spot the Great Orion Nebula, although binoculars will enhance the view. Look just south of the three familiar stars that form Orion’s Belt. Don’t expect to see the vibrant reds and blues shown in long-exposure photographs of M42. At night, the human eye’s color receptors are not activated, so even the colorful Orion Nebula appears a pale gray.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College’s Alpine Campus. He is an avid astronomer whose photographs and articles have been published around the world. Check out his website at www.jwestlake.com.