Orion the Hunter
February 2011 :
Everyone with an interest in astronomy probably has a favorite constellation. It may be because of the star pattern’s mythology, or its shape in the sky, or for the beautiful objects that reside within its boundaries, or possibly because it’s your astrological sign.
One of my favorite constellations is the most prominent star pattern in the winter sky—Orion, the mighty hunter. And during February around 8:00 pm, Orion can be found about halfway above the southern horizon. (See accompanying star map.) Though Orion rises on his side, only when he is due south of our location is he standing upright. With the exception of the Big Dipper (Ursa Major) and Scorpious, Orion is probably the most recognizable of star patterns. He is also the brightest of all the 88 constellations.
In addition, Orion is quite a large constellation. I thought it was at least among the top ten in area (square degrees), but I was incorrect. Orion covers 594 square degrees, ranking it 26th. The top three are Hydra (1302), Virgo (1294) and Ursa Major (1280).
The mythology of Orion, like many of the older northern hemisphere constellations that date back to the early Greeks and Romans, is quite extensive. I suggest you consult Wikipedia for further details on Orion’s origins.
Before we explore one of the most beautiful celestial objects visible to amateur telescopes (and the determining factor for Orion being one of my favorite constellations), let’s examine some of the major stars that comprise this sky pictogram.
The prominent red star Betelgeuse marks Orion's eastern shoulder (top left, from our perspective) and Bellatrix marks the western one (top right). Betelgeuse, which means “the armpit of the central one,” is a very large red giant star at a distance of 520 light years, measuring in at a conservative 950 solar diameters. It coincidentally resides in a “giant” of a constellation. If you replaced our Sun with Betelgeuse it would extend out to the asteroid belt between Mars and Jupiter.
Blue-white supergiant Rigel resides 800 light years away and is positioned at Orion's western heel (bottom right), while Saiph is at the eastern one (bottom left). Rigel, in Arabic, means “the left leg of the giant.” West of Bellatrix is a curved group of eight stars that represents Orion's shield. Contained within the rectangle formed by Betelgeuse, Bellatrix, Rigel and Saiph is a string of three stars that comprises Orion's belt. Just below the belt you'll find Orion's sword, made up of a small group of stars.
The grandeur of Orion resides in the region of his sword. Using binoculars you'll see a wispy, hazy patch of green light enshrouding the stars. Using a telescope even under low magnification will reveal a greenish tinged nebula of dust and gas, the magnificent Orion Nebula (see photo insert).
You’ll be amazed at the intricate swirls of nebulosity, especially on a moon-less night in a dark country sky. The nebula complex lies about 1,400-1,500 light years distant and is about 30 light years across. You'll also immediately notice four bright stars embedded in the nebulosity. This asterism is called the Trapezium. These four stars are “youngsters” in the universe—only about one million years old. They formed out of some of the gas and dust in the nebula. Approximately 1,000 other stars share a space of about four light years in diameter with the Trapezium stars. That’s crowded real estate!! And more suns will coalesce out of this stellar nursery in the future.
No one has described the humbling effect the Orion Nebula has on us amateur astronomers any better than Garrett P. Serviss in his 1901 book Pleasures of the Telescope.
“Nowhere else in the heavens is the architecture of a nebula so clearly displayed....The work of creation is proceeding within its precincts. There are stars apparently completed, shining like gems just dropped from the hand of the polisher, and around them are masses, eddies, currents, and swirls of nebulous matter yet to be condensed, compacted, and constructed into suns. It is an education in the nebular theory of the universe merely to look at this spot with a good telescope. If we do not gaze at it long and wistfully, and return to it many times with unflagging interest, we may be certain that there is not the making of an astronomer in us.”
Did you receive a telescope for Christmas? It will most likely be cold outside during February, but I would suggest that the Orion Nebula be your first celestial target. Then you can decide for yourself whether or not Serviss' description still does justice to the magnificence of this nebula today.
The Orion Nebula looks absolutely wonderful with some of the larger instruments at the local observatories. Seagrave Memorial Observatory (http:/www.theskyscrapers.org) on Peeptoad Road in North Scituate is open every clear Saturday night for public viewing from 7-9pm during the winter. Ladd Observatory (http://www.brown.edu/Departments/Physics/Ladd/) in Providence is open every clear Tuesday, from 7-9pm during the winter as well.
While it can be quite cold observing in these unheated domes, these facilities do remain open year-round, provided inclement weather does not force closures or the grounds are inaccessible. Please check their respective websites for any cancellation notices before venturing out for a visit.
As always, keep your eyes to the skies.
