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The Fuzzy Star

If you look up into the sky to the east any time after 9 PM on a clear night, you can see the greatest of the constellations Orion the Hunter. While Orion's head and hands are delimited with third and fourth magnitude stars, Orion's torso from his shoulders to his knees are picked out by some of the brightest stars in the heavens - Betelgeuse [left shoulder], Bellatrix [right shoulder], Alnitak [left belt], Alnilam [belt buckle], Mintaka [right belt], Rigid [right knee] and Seraph [left foot] are all second magnitude stars or brighter stars. In Arabic mythology, Orion was the greatest of the giants, with Castor and Pollux [ the Gemini] as his slightly smaller companions.

With all these bright stars to stare at you might be tempted to miss a relatively dim star Theta Orionis, the middle star of the sword which hangs down from Orion's belt, just inside his left leg. It is difficult to focus on this fuzzy star and no wonder because it isn't a single star at all but the greatest stellar nursery visible in the northern hemisphere [called Messier 42 {M42} or the Great Orion Nebula]. Even the most modest optical instruments will resolve Theta Orionis into two stars Theta 1 Orionis and Theta 2 Orionis. The whole area seems to be bathed in a faint but glowing haze. With slightly more powerful instruments, Theta 1 Orionis suddenly resolves itself into 4 brilliant pinpricks in the shape of a trapezoid (a rectangle with one of the two long sides shorter than the other). With yet more powerful instruments like the Frosty Drew 16" Meade Schmidt Cassegrain, two more stars can faintly be seen in the Trapezium. With our selection of special filters, the haze becomes clearly delimited as great shinning clouds and dark crevasses.

If we climbed into the Kuiper Airborne Observatory, a telescope mounted in the side of a Boeing 707 and flew to the highest operating altitudes (above 40,000 feet) where the air has thinned to 1% of the density in Charlestown, we would be above all the moisture which absorbs most of the infrared light from M42. Suddenly more than a hundred stars appear in the dusty glowing cloud. For stars which measure their lifetimes in millions and billions of years, these newly formed stars just beginning to shine are infants.

Stellar nurseries start as great clouds of hydrogen and helium gas with traces of other elements. When these clouds encounter magnetic lines of forces wheeling from the center of the galaxy, or the clouds are compressed by nearby supernova (huge stellar explosions), they become dense enough to allow gravity to complete the job of compressing them into stars. Initially, these stellar nurseries are tightly packed with infant stars. The natural movements of the stars eventually spread them apart until the become a loose open cluster such as the Pleiades or the Hyades in Taurus. Eventually the stars spread apart into huge groupings that often loose any apparent connection. There is some evidence that the stars of the Big Dipper and Sirius, the brightest star of all, in the south belonged to the same grouping millions of years ago.

Here is a tip from a seasoned observer - don't rush things when you look at a very special object like Trapezium imbedded in the Great Orion Nebula. Train your eye to look at something at the edge of the object and you will be amazed at how much more detail becomes visible. In daylight the color sensitive receptors (the cones) have more than enough light to see but in dim light the much more sensitive black and white receptors (the rods) see details that would otherwise be lost. You won't cause anyone to miss their turn at the telescope if you spend an extra 20 or 30 seconds examining rather than glancing at a deep space wonder. You will see things that 90% of our visitors miss no matter how we urge them to look for details.

Frosty Drew Observatory is open clear Friday nights throughout the winter except for the week between Christmas and New Years. Dress warmly when you come. We open the Nature Center to allow people to warm themselves whenever the temperature is bitter. You'll be among the relatively few hardy souls who have discovered that cold weather means short lines and more chances to see deep space wonders.

Leslie Coleman
Author:
Leslie Coleman
Entry Date:
Nov 1, 2000
Published Under:
Leslie Coleman's Columns
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