Categorised in: Science
Orion the Hunter is the king of the constellations, as far as I’m concerned. I’m far from the only one with that opinion.
In the minds and imaginations of many, many stargazers all over the world, Orion is at the top of the constellation pyramid. Even if you’re not all that much into stargazing, you can’t help but notice the mighty celestial hunter prowling westward across the winter heavens.
It’s one of the few constellations that actually resembles what it’s supposed to be. With just a passing glance you can easily see the torso of Orion with his broad shoulders and gigantic thighs. I have to be honest, though. To me, Orion also resembles a giant hourglass oriented diagonally in the evening southeastern sky.
In this week’s column, I want to tell you about some of Orion’s many astronomical treasures. Next week I will share some of the great mythological tales involving the great constellation.
Orion’s great calling card is, without a doubt, his belt, made up of three bright stars close together in nearly a straight line. Even though the belt’s stars — Alnitak, Alnilam, and Mintaka — look close together, they are physically nowhere near each other. Not only are they hundreds of light-years from Earth, but they are also hundreds of light-years from each other. Call it a celestial coincidence or divine intervention that these stars line up as orderly as they do from our heavenly perch in our part of the vast Milky Way galaxy.
Below the stars in Orion’s belt, there are three more stars in a short line that aren’t quite as bright. That trio makes up Orion’s sword, and without too much eyestrain, you can see that the middle star is “fuzzy.” Actually, that’s not a star. It’s a star factory, or nursery, called the great Orion Nebula. It’s nearly 1,600 light-years away (one light-year equals nearly 6 trillion miles).
The Orion Nebula is a gigantic cloud of hydrogen gas, and with a small telescope or even a decent pair of binoculars, you can see a tiny cluster of four stars near the center. These infant stars were born gravitationally out of this giant mass of hydrogen gas during the last several million years, although one of the stars may be as young as 50,000 years old, which is extremely young when you’re talking stellar. The Hubble telescope has even detected what may be planets developing around the new stars.
The reason we see the Orion Nebula as well as we do is that it’s literally being lit up like a neon light. The very young and extremely active stars hidden within the nebula are emitting so much intense radiation that the atomic structure of the surrounding gas is disrupted, causing it to glow brightly. Actually, we’re seeing just a small part of the Orion Nebula. There’s a lot more that isn’t glowing, but thousands and thousands of stars are still forming within it, nonetheless.
(Courtesy of Mike Lynch)
Another one of Orion’s celestial hallmarks is the bright star Betelgeuse, located in the upper left corner of the hunter. Like many stars, Betelgeuse has an Arabic name. Arabic culture in the Middle Ages and earlier cataloged the night sky, and many of those traditional star names are still in use today. What I love about the name Betelgeuse is that it roughly translates to English as “armpit of the great one.” As you can see in the diagram, Betelgeuse actually marks the armpit of Orion.
Astronomically Betelgeuse is one of the single biggest things you’ve ever seen. It’s considered a super red giant star, and even with the naked eye, you can detect its reddish hue. Betelgeuse fluctuates in diameter from about 400 million miles to nearly a billion miles in girth. Our own home star, the sun, isn’t even a million miles in diameter.
Betelgeuse is nearly 600 light-years from Earth, and it is dying a slow death that someday will turn extremely violent. At present, it’s using up all of the hydrogen and helium fuel in its core. When that happens to extremely massive stars like Betelgeuse, they become extremely unstable, and eventually the star explodes in a spectacular fashion. This is called a supernova explosion. Many astronomers think this could happen to Betelgeuse within a million years — or maybe even next week. I wouldn’t wait up for it outside in your lawn chair, though. You could turn into a popsicle!
There’s a lot more astronomical treasure in the constellation Orion, but its belt, the Orion Nebula and Betelgeuse are the big three. What I also love about Orion are all of the other bright stars and constellations that surround the great heavenly hunter. I like to call this part of the sky “Orion and his gang.” I just love this part of the night sky, and I know you’ll fall in love with it, too.
Next week, the lore of Orion.