The Great Orion Nebula
The waning crescent moon reaches new phase Monday, leaving our night skies free of its overpowering glow. As darkness settles and the stars come into view, the familiar outline of Orion is appears above the southeast horizon.
Easily the most recognizable constellation, Orion has marched through the heavens and played a role in the mythology of every civilization and culture on earth.
Each of the constellation’s stars is magnitude 2 or brighter, and it holds the seventh-brightest star, Rigel, at the hunter’s right foot, and the 10th-brightest, Betelgeuse, juxtaposed at the figure’s left shoulder.
Perhaps even more prominent than this bright pair are the three aligned belt stars, Mintaka, Alnilam, and Alnitak, dissecting Orion’s hourglass shape. Dangling from the hunter’s belt is a fainter trio of stars that forms his sword. To the unaided eye, the middle of these three stars, at magnitude 4, appears a bit fuzzy, belying its true identity.
The Great Orion Nebula, dubbed M42, is in fact a massive stellar incubator, a vast cloud of gas and nascent stars spanning 20 light years — 15,000 times the size of our solar system — and more massive than 10,000 of our own suns.
In binoculars or a small telescope, the nebula appears as a grey blob. Observed with a larger scope, it is a great glowing cloud, one of the most beautiful sights in the heavens, alive with red and green.
What you’re seeing is no single star’s light, nor even starlight. Instead, it is the heat and radiation from myriad young stars charging the surrounding gas and illuminating it in much in the same way as a fluorescent light bulb or as the setting sun changes the color of the clouds.