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Magnificent Orion

The spectacular parade of planets that marched across the Fall skies has nearly disappeared. Venus and Jupiter set shortly after the Sun. Only that old slowpoke Saturn remains high in the sky. No great comets are visible. The Moon waxes and wanes. Does that mean that there is nothing in the sky worth a trip over to Frosty Drew Observatory? Far from it! Winter is the domain of that most glorious of constellations, the Great Hunter Orion. Orion is an entire wonderland of stars, stellar nurseries, dying super giants, and gaseous nebulae by itself.

Orion is located directly over the Equator. The black line you see across the middle is where the Earth's Equator would be projected on the sky. The three bright stars just below the equator (called the belt) are just above one of the sky's truly magnificent spectacles, the Great Nebula in Orion. This patch of gas is a huge stellar nursery.

Imbedded in this gas are new stars, scarcely more than babies as stars go. One of these stars (Theta Orionis) reveals itself as two in a pair of binoculars. In a moderate telescope one of these two stars again reveals itself as a grouping of four bright stars arranged in a trapezoidal (diamond) shapes called appropriately the Trapezium. In yet more powerful telescopes each of these stars in turn are double stars.

The great red star that form Orion's shoulder holding his huge club is Betelgeuse (beetle juice). Unlike the infant stars in the sword of Orion, old Betelgeuse is nearing the end of its life. It has led a life of reckless consumption of its budget of hydrogen fuel. As it burns the last of its fuel it is swelling to a huge radius. Astronomers believe that it is so large that if it were centered where our Sun is, that it would swallow up the planets Mercury, Venus and Earth. It's radius extends almost as far as Mars. It is truly a giant!

Across Orion is Rigel, another giant of a star. In this case, Rigel is bright blue white. Like Betelgeuse, it is burning its budget of hydrogen at a spendthrift rate. Rigel is one of the brightest stars in the sky in spite of being more than 900 light years away. (That is a bit more than 5,400 trillion miles). In fact, if Rigel were located where Sirius (the brightest appearing star) is, it would be more than 11000 times as bright. If our poor little Sun were to replace Rigel, we couldn't see it with the unaided eye!

Orion isn't through with its list of wonders. Just below the lowest star in the belt is the Horsehead Nebula, a dark cloud shaped like a horse's head which shades a brighter gas cloud. Nearby is the Flame Nebula. Just above these two nebula is another gas cloud M78 sitting on the celestial Equator. Just under Orion's club is a loose grouping of stars called NGC2169. In front of the bow is NGC1662, another loose cluster. These loose cluster's are stars which once were in stellar nurseries where the gas has largely evaporated. These stars are still young, but not infants like the Trapezium.

If you can't get over to Frosty Drew Observatory on a starry Friday evening, don't deprive yourself of these treats. Get a pair of binoculars and see how much detail you can make out. You'll be surprised what you can see. Orion is worth bundling up warmly for a view.

Leslie Coleman
Author:
Leslie Coleman
Entry Date:
Jan 1, 1998
Published Under:
Leslie Coleman's Columns
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