ORION RISES IN THE SOUTHEASTERN SKY IN DECEMBER
I’m excited to write about the constellation Orion for the December issue. Orion is the favorite constellation of many people. Orion’s stars are brilliant. Furthermore, the constellation lies across the Celestial Equator, so it can be seen by anybody anywhere on Earth at the right time of year.
We need a few definitions. These are taken from www.skymaps.com.
Constellation: “a defined area of the sky containing a star pattern” (such as a person, animal or object).
Galaxy: “A mass of several billion stars (or more) held together by gravity.”
Celestial equator: An imaginary line created by extending the Earth’s equator far out into space. (my definition)
Quoting from the Audubon Society Field guide to the Night Sky, “Orion’s bright stars have been identified as a person by civilizations worldwide for thousands of years. It is mentioned in poetry as early as the Odyssey and more recently by Longfellow.
Orion is mentioned in the Bible, Job 38:3, “Canst thou bind the sweet influences of Pleiades, or loose the bands of Orion?”
Early Greek and Roman cultures believed that the Constellation’s stars represented a hunter. There are stars that are in the right place to represent shoulders, feet, belt and sword.
The star named Betelgeuse (pronounced beetle-juice) forms one of the shoulders. It is the bright reddish star on the left as we would see it. The name is Arabic, meaning “the shoulder of the great one.”
Betelgeuse is an amazingly huge, red super-giant star. Its reddish color indicates that its temperature is low compared to most other stars. In contrast, the really super-hot stars have a bluish tint. This is different from the colors on our plumbing fixtures, where hot is indicated by red and cold by blue. It’s quite confusing. I need to keep reminding myself that in the sky, reddish means cool and blue means hot or super-hot.
Betelgeuse is classified as a “red supergiant,” 692 million miles in diameter, meaning that 256 million stars the size of our Sun could fit into its boundaries.
In large binoculars or medium-size scopes and larger, it appears as a disk rather than just a dot.
Rigel, (Arabic for foot) is located on the lower right. It is a hot-blue star, thirty times the diameter of our Sun and it puts out 50,000 times the light energy of our Sun.
Rigel is classified as a blue super-giant and it is using up its nuclear fuel at an enormous rate. Its life span is limited. It will only last millions of years, rather than billions of years. Our Sun is believed to be about 5 billion years old with 5 billion more to go. Alas, we won’t be around.
Orion can be seen (if it’s clear) in early December above the eastern horizon when it’s dark. Look just a little to the right (south) of east. Orion will look like a giant just rising from sleep, ready to dominate the southern sky for the entire night.
For a little more fun, follow the line of the 3 stars of Orion’s belt up. First you will see the Hyades Cluster with some beautiful scattered stars. Farther on the line you will run into the 7 Sisters. Use binoculars if you have them. I guarantee you that will knock your socks off.
A person could spend many years finding out more about Orion, its stars, luminous clouds, etc. I will tell you more in February. For further study, get the fact-filled book, The Audubon Society Field Guide to the Night Sky. Happy Observing!