The Astronomy of a constellation

Next to the Big Dipper, the constellation Orion is the most recognized group of stars in the night sky. It is hard not to notice this bright constellation even if your skies are plagued with neighborhood lights. Orion is not only an easily recognizable group of stars; the stars and objects within the constellation are an astronomy lesson in themselves!

In Greek mythology, Orion was a great hunter. It was said that the mighty Orion claimed superiority over all creatures on Earth. The gods were angered by this arrogance and sent a scorpion to punish Orion. The scorpion bit Orion in his heel, (Achilles?), and killed the mighty hunter. But Dianna, the moon goddess, felt sorry for Orion and requested that the hunter be placed in the sky where all could admire him. The gods agreed, but as a reminder to warn that none are infallible, they placed the scorpion in the sky also, he is known as Scorpius. Scorpius is about in the summer skies and, perhaps as a final pity to Orion that he should never again see his killer, the two constellations can never be seen in the sky at the same time.

Orion may not have been superior to all creatures on Earth, but he is certainly superior to all other constellation in the sky, having more bright stars than any other. Rigel and Betelgeuse (pronounced beetle juice) are the two brightest stars. Betelgeuse, is the star in the upper left corner of Orion and is the first star (other than the Sun) to have its diameter measured. Betelgeuse turned out to be a whopping 800 times the size of our Sun, a type of star known as a red supergiant. Rigel is at the lower right corner of Orion. Rigel is a giant blue star many thousands of times brighter than the sun.

Most constellations are made up of stars that are actually nowhere near each other in space, but appear to us to be near each other because they are in the same line of sight. But the three bright stars in a horizontal row for the belt of Orion and the fainter stars in a vertical row beneath the belt are all related. They are giant young stars that have all formed from the same nebulae. The actual birthplace of the belt stars is in the vertical row below. If you have binoculars, look at the middle of these stars. You will see a fairly bright hazy cloud. This is the great Orion nebula. A small telescope will show a breathtaking sight. From these clouds, stars are "born." The ones in the belt are even younger than the Pleiades mentioned in an earlier article.

It is somewhat ironic, that just as in the myth, Orion had to pay a price for all that boasting, the giant stars that make up the constellation will also pay a price for all that size. The bigger a star is, the faster it burns, and the shorter it’s lifespan. Our Sun is medium size, and will burn steadily for another 5 billion years or so. But stars as big as Betelgeuse, measure their lives in terms of millions of years. And while our Sun will meet a quiet and slow end, for Betelgeuse and many of the Orion stars, the end will be explosive. These stars will eventually explode as what is called a supernova. Betelgeuse will undoubtedly be the first of the Orion stars to go, being already elderly in star terms.

Look for Orion high in the southeast around nine PM. It is just to the east of Taurus the bull, in which the Pleiades reside. Whether you like to learn the astronomy behind the constellations, or just like to learn your way around the sky, Orion is truly a gift to behold.