Domination is the best way to describe the role of Orion the Hunter in the winter heavens. Out of the nearly seventy constellations we can see from Minnesota and Wisconsin over the course of the year, it's the big guy, the godfather! I know you've seen it even if you didn't know what you were looking at. In fact, it's probably the most recognized constellation in the sky.
If you were to walk down the street and randomly ask somebody to name a constellation, chances are they'll pretend not to hear you, or give you "the look". If they do acknowledge you they'll probably say the Big Dipper. The problem is that the Big Dipper is technically not a constellation. It's actually the tail and the derriere of the constellation Ursa Major, otherwise known as the Big Bear.
A few folks might mention Orion as a constellation, and for sure that is a complete constellation. Even if you haven't paid all that much attention to the winter night sky I know you've seen Orion. At first glance it reminds you of an hourglass with the neck made up of a short straight line of three bright stars.
According to Greek and Roman mythology, the three stars in a row make up the belt of the hermit hunter and the hourglass is the outline of Orion's torso. This time of year my favorite constellation, my celestial buddy, starts out in the southeastern sky after evening twilight and stalks his way westward through the rest of the night. By around 4am Orion slips below the western horizon. It's appropriate that we see Orion during most of these long winter nights because, according to mythology, he was a half god half mortal who slept by day and hunted by night.
Astronomically, Orion is legendary because of its numerous celestial treasures. It's the home of many bright stars, star clusters, and nebula. Its hallmark is that perfect line of three stars in a diagonal row that make up the hunter's belt. Nowhere else in the sky will you find anything like it. From the lower left to the upper right the stars are Alnitak, Alnilam, and Mintaka. What's amazing is that while these stars are so perfectly lined up, they physically have nothing to do with each other; in fact, they're nowhere near other. By an incredible astronomical coincidence they just happen to be in the same line of sight. Alnitak is 800 light-years from Earth. Alnilam is about 1300 light years away, and Mintaka is nearly 690 light years away from our cold backyards. They are physically different from each other as well. Alnitak and Mintaka are actually both multiple star systems with Mintaka made up of at least five stars revolving around each other.
Orion's brightest star, Rigel, resides on the hunter's left knee and is a bright blue giant star more than 770 light years away. It's believed to be a very young star, possibly only ten million years old or so. Our own sun is thought to have been around for about six billion years. It's much larger and more powerful than our home star, almost 100 times larger than our sun and possibly more than a hundred thousand times as luminous!
The second brightest star has one of the best star names in the sky, Betelgeuse, pronounced by most as "beetle-juice." It shines in Orion's armpit. In fact, Betelgeuse is an Arabic name which means "armpit of the mighty one". Even with the naked eye, you can see that Betelgeuse is a red giant star. It's actually a giant among giants, possibly over a billion miles in diameter or more. It's the biggest single thing you can see from Earth with the naked eye! Betelgeuse is also nearing the end of its life. Sometime between now and the next million years, Betelgeuse will explode in a tremendous supernova explosion. Here on the Earth, just over 600 light-years away, we'll be almost close enough to get some of the cosmic fallout. Just what we need, something more to worry about!
While Betelgeuse may be dying, there's also new life in Orion. Look below Orion's belt for the three fainter stars that outline the hunter's sword. You can't help but notice that the middle star in the sword is fuzzy. That's because it's not a star but a nebulae, a 30 light-year wide cloud of hydrogen gas and dust almost 1500 light-years away. It's more than 20 times the diameter of our solar system and within it, before our very eyes, stars are being born. It's a stellar cosmic womb and nursery. All through our own galaxy and millions of other galaxies in our universe, stars form out of hydrogen nebulae. Because of gravity, globules of hydrogen begin to collapse, which creates compression. If it's massive enough, heat due to the compression will fire up nuclear fusion and presto, you have a star, shining brightly for billions of years. Nebula, depending on their size, can produce hundreds and hundreds of stars. The Orion Nebulae is so big it could produce over 10,000 new stars!
Using even a small telescope, maybe one you got for Christmas, you can see four new stars that have formed in the great nebulae of Orion. It's called the Trapezium since the four stars are arranged in a tiny trapezoid-baseball diamond shape. These stars may be only 300,000 years old and are showing signs of developing new solar systems. In fact, it's debated that one of the stars may be less than 50,000 years old. There's a lot going on in that fuzzy little star below Orion's belt.
There are a lot of other celestial treasures in Orion like the Horse Head Nebula and the Running Man Nebula that require large telescopes and diligence to see, but they are well worth the effort!
Diagram of Orion...Click