A stellar ‘Baby factory’
The Orion Nebula is one of the best “must-see” attractions in the Butler night sky, and it’s even more impressive once you get to know more about this gargantuan star factory. There’s enough material there to produce at least 10,000 stars, each the size of our sun. It’s more than bright enough to see with the naked eye and very easy to find.
Just as the name implies, the nebula resides in the great constellation Orion the Hunter. Even if you’re not all that constellation savvy, you’re probably familiar with Orion, the mighty hunter with the three bright stars in a row that outline his belt.
This time of year, Orion is at its maximum altitude in the southern sky around 8 p.m., and you can’t help but notice the posse of bright stars and constellations that surround the hunter. If you’re a frequent reader of this column, you know that I lovingly refer to this part of the sky as “Orion and his gang.”
There are even planets in the mix this year. Jupiter is very bright, and is perched to the upper right of Orion. To the upper left, Mars, with its definite orange-red hue, is the brightest starlike object you can see this month.
The Orion Nebula is in the sword of Orion, which hangs below the belt. Just like the hunter’s belt, the sword also is depicted by three stars in a row, but they’re not quite as bright as the belt stars. They’re certainly easy enough to see though. If you look closely at the middle star in the sword, you’ll see that it’s a “fuzzy star.” That’s it, the Orion Nebula!
There’s a heck of a lot more to this “fuzzy star” than meets the eye. Astronomers estimate that the nebula is more than 1,300 light-years away, with just 1 light-year equaling almost 6 trillion miles. That’s so far away, that the light we see from it tonight left the Orion Nebula in the eighth century.
If you hold out one of your thumbs at arm’s length, it should easily cover up the Orion Nebula. That thumb of yours is covering a giant cloud of hydrogen gas, well over 20 light-years in diameter. That’s almost 180 trillion miles — or about 20,000 times the diameter of our entire solar system. Your thumb is covering all of that!
With even a small telescope or a decent pair of binoculars, you’ll see that the giant cloud of gas surrounds a cluster of stars within it.
If your optics are powerful enough, you’ll see that cloud has a greenish tinge to it and that the cluster is made up of four little stars arranged in a trapezoid. These four stars, also known as the Trapezium, were born out of this giant cloud of hydrogen gas an estimated 10 to 100 million years ago. This makes them stellar infants. Our own sun, about 5 billion years old, is considered a middle-aged star by comparison.
All stars are born out of clouds of hydrogen gas. Randomly dense gas globules within the nebula develop and gravitationally collapse and compress to become stars. As these balls of gas grow, their internal gravitational pressure and heat build to unthinkable levels, causing nuclear fusion to fire up in their cores, and stars are born. That’s what happened to our closest star, the sun.
Also, there’s strong evidence of developing solar systems around some of the stars of the Trapezium. The trouble, though, is that these potential planets may not come into being. Stellar winds gusting over 5 million miles an hour are constantly blasting away any semblance of developing planet families. In fact, tremendous stellar wind currents from several stars can collide to cause a perfect cosmic storm, resulting in complete celestial chaos.
The surrounding hydrogen glows the way it does due to the tremendous amounts of radiation that emanates from these new stars. They are very hot, with estimated surface temperatures of 72,000 degrees, more than seven times the temperature of our sun. All that heat and radiation pouring out of these four stars and others cause the surrounding hydrogen gas to glow like a giant neon light. Astronomers refer to this kind of nebula as an emission nebula.
As impressive as the Orion Nebula is, it’s just the tip of a huge celestial birthing ground. We only see the lit-up part of the nebula. It’s actually several hundred light-years in extent and occupies over half the entire constellation of Orion.
Inside the nebula, out of sight for now, stars are being born, and many more stars will emerge out of it in the future. Some stars may be like our sun, and some planets around those stars could evolve the same way that Earth did. Who really knows? It’s unlikely current generations will ever know. Tell your great-great-great-grandchildren to stay tuned!
In the meantime, enjoy the beauty that is the great Orion Nebula in the late winter heavens.
Mike Lynch is an amateur astronomer and professional broadcast meteorologist for WCCO Radio in Minneapolis/St. Paul. He is also the author of “Stars: a Month by Month Tour of the Constellations,” published by Adventure Publications and available at bookstores and at adventurepublications.net. Contact him at mikewlynch@comcast.net.
