Orion, the king of the winter sky, part 1
The constellations of winter are simply the best. Nowhere else in the Butler night sky will you see as many bright stars and bright constellations packed so closely together. The constellation Orion is the best of the best in my book! I know you've seen it, even if you didn't know what you were looking at. If you randomly ask somebody to name a constellation, chances are they'll say the Big Dipper or Orion.
Technically, the Big Dipper isn't actually a constellation. It's just part of the larger constellation Ursa Major or the Big Bear. The Big Dipper outlines the derriere and tail of the bear and is undoubtedly the brightest part of the constellation. Orion, however, is a complete constellation. At first glance, it may remind 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, begins the evening in the southeastern sky after evening twilight and forges his way westward through the rest of the night. By around 4 a.m. 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. I'll have more on the legend of Orion in next week's Skywatch column.
Orion is also legendary astronomically with its treasure trove of wonderful celestial treasures. It's the home of many bright stars, star clusters and nebulae.
Orion's calling card is a 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. The stars are Alnitak, Alnilam and Mintaka from the lower left to the upper right.
What's amazing is that while these stars look so perfectly lined up, they physically have nothing to do with each other; in fact, they're nowhere near each other. By an incredible astronomical coincidence, they just happen to be in nearly the same line of sight.
Alnitak is at least 800 light-years from Earth and maybe as far away as 1,300 light-years. Alnilam is near 2,000 light-years away, and Mintaka is over 1,200 light-years away from our cold backyards. They are physically different from each other as well.
As with most stars we see with the naked eye, all three of the belt stars are in reality multiple star systems. Mintaka is at least five stars in reality, all revolving around each other.
Orion's brightest star, Rigel, resides on the hunter's left knee. A bright blue giant star more than 860 light-years away, Rigel is believed to be the largest star in a four-star system. It's a very young star, possibly only 10 million years old, or so, and our sun has been around for about six billion years. It's much larger and more powerful than our home star, almost 70 times the sun's diameter 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, a red supergiant star, is pronounced by most as “beetle juice.” It marks Orion's armpit. Betelgeuse is an Arabic name that roughly translates to “armpit of the mighty one.” Even with the naked eye, you can see Betelgeuse's reddish hue.
At least 700 million miles in diameter, Betelgeuse is a giant among giants, one of the biggest single things you can see from Earth with the naked eye! The big star is nearing the end of its life. Sometime between now and the next 100,000 years, Betelgeuse will blow up in a tremendous supernova explosion. Here on Earth, more than 500 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 nebula, a vast cloud of hydrogen gas and dust being lit up like a fluorescent light by the energy of brand new stars. The Orion Nebula is 1,400 light-years away from Earth, and at least 25 light-years in diameter, more than 20 times the diameter of our solar system. Within it, before our very eyes, stars are being born. It's a stellar cosmic womb and nursery.
Stars form from hydrogen nebulae throughout our galaxy and billions of other galaxies in our universe. Because of gravity, globules of hydrogen within the nebula begin to collapse, creating extremely high pressure at the centers of the globules. If they're massive enough, the heat and pressure in the core will fire up a nuclear fusion furnace, and presto, you have a star shining brightly for billions of years. Depending on their size, nebula can produce hundreds and hundreds of stars. The Orion Nebula is so enormous it could create thousands!
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 show signs of developing new solar systems. There is 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. Both require large telescopes and diligence to see, but they are well worth the effort!
Next week I'll tell you the story of Orion, the magnificent heavenly hunter.
Mike Lynch is an amateur astronomer and retired broadcast meteorologist for WCCO Radio in Minneapolis/St. Paul. He is the author of “Stars: a Month by Month Tour of the Constellations,” published by Adventure Publications and available at bookstores and adventurepublications.net. Contact him at firstname.lastname@example.org