The Orion Nebula is one of the best “must-see” attractions in the sky, and it’s even more impressive once you know more about this gargantuan star factory.
It is made up of enough material to produce at least 10,000 stars the size of our sun. It’s more than bright enough to see with the naked eye, and it’s very easy to find. Just as the name implies, the nebula resides in the great constellation, Orion. 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, and you can’t help but notice the posse of bright stars and constellations surrounding 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’s even a planet in the mix. Mars is the next brightest star-like object you can see above Orion’s head.
The great Orion Nebula is in the sword that hangs below Orion’s belt. Like the belt, the sword is depicted by three stars in a row, but they’re not quite as bright as the belt. They’re certainly easy enough to see, though, and if you look closely at the middle star in the sword you’ll see that it’s a fuzzy star. That’s the Orion Nebula.
There’s much more to this “fuzzy star” than meets the eye. Astronomers estimate that the nebula is more than 1,500 light-years away (Just one light-year equals almost 6 trillion miles). It’s a long way out there.
If you hold out your hand at arm’s length, your thumb should easily cover up the Orion Nebula. Your thumb is covering a giant cloud of hydrogen gas, more than 30 light-years in diameter. That’s almost 180 trillion miles in girth, or about 20,000 times the diameter of our entire solar system. Your thumb is covering up 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 the cloud has a greenish tinge, 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 five 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, nuclear fusion fires up in nuclei, causing stars to be born. That’s what happened to our sun.
In the last 15 years or so, the Hubble telescope has detected 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 at more than 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, otherwise known as complete celestial chaos.
The surrounding hydrogen glows the way it does due to the tremendous amounts of radiation that emanate 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 the 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 lighted part of the nebula, which spans about 30 light-years. It’s actually several hundred light-years in extent and occupies more than half of 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 the current generations will ever know. Tell your great-great-great-grandkids to stay tuned.
In the meantime, enjoy the beauty that is the Great Nebula of Orion in the late winter heavens.
Mike Lynch is an amateur astronomer and professional broadcast meteorologist for WCCO Radio in Minneapolis and is author of the book, “Washington Starwatch”, available at bookstores and at his Web site, www.lynchandthestars.com
The Everett Astronomical Society welcomes new members and puts on public star parties. Their Web site is: members.tripod.com/everett_astronomy.
Talk to us
> Give us your news tips.
> Send us a letter to the editor.
> More Herald contact information.
