By David Ward
It has been called the Backbone of the Night. The Cherokee Indians thought it was cornmeal strewn across the sky by a giant dog. The Greeks believed it to be spilled breast milk from a divine goddess. The philosopher Aristotle insisted it was “the ignition of the fiery exhalation of stars in the upper atmosphere.” Galileo was the first person to view it through a telescope and saw a “mass of innumerable stars.”
Today we call it the Milky Way galaxy, our home in the vast cosmos. Go out on a clear, dark, moonless and smoke-free night away from distracting lights. Give your eyes a few minutes to adjust to the darkness and then look for a band of light stretching from north to south all the way across the sky. Light pollution has erased this grand view from many locations around the globe. Here in the Methow Valley we are fortunate enough to still be able to see one of the most inspiring sights in the night sky.
So what is up there anyway? Imagine a giant conglomeration of stars shaped like a pinwheel with two spiraling arms projecting out of a central bulge. That glow overhead is one of those spirals arms and it has literally billions of stars in it. Follow that glow down low in the south to the central bulge of the pin wheel, the center of our galaxy.
It is hard for us who live on this tiny chunk of rock we call the earth to really grasp the size of our galaxy. I could say that a beam of light traveling at 186,000 miles per second would take 100,000 years or more to traverse its vast breadth, but that does not help at all. The numbers are way too big.
Here is another idea. Let’s make a scale model of the Milky Way galaxy using a grain of salt to represent each individual star. Sounds simple, right? Maybe it would fit right on your living room floor — after all, it is a huge reduction of scale. Stars are big. Our sun, a small, puny little thing as far as stars go, is 864,000 miles across and a grain of salt is tiny.
You are going to need a lot of salt. Probably more than you can buy at your local grocery store. Plan on getting a few dump truck loads, about 40,000 pounds would do it. Maybe this is not going to fit in your living after all. How big would your model have to be? Would it fit into Okanogan County? Think bigger! How about the Pacific Ocean, the largest geographical feature on earth? Not even close! Your model would need a space the size of the orbit of the moon around the earth, a space almost 500,000 miles across!
If all this sounds in incomprehensible, here is a quick takeaway. That glow stretching across the summer night sky is gigantic!
Where do we fit into this vast structure? Our sun, pulling the earth along with it, is cruising through the galaxy at a speed of 500,000 miles per hour. Currently we are located between the two big spiral arms on the edge of a sub-structure known as the Orion Spur. I know living on a spur does not sound very glamorous but it is really a great place to be. If we were in one of those arms, it would be like Interstate 5 at rush hour except every one would be going at hundreds of thousands of miles per hour. Anything could happen, like exploding stars or colliding black holes or gamma radiation bursts, that could imperil the delicate commodity we call life which happens to inhabit our little planet.
It turns out we live in a quiet, out-of-the-way part of the galaxy. Think of it as the Methow Valley of the Milky Way and that is a great place to be.
Two magnificent planets are out there these summer evenings. Look for Jupiter low in the southwest just as it gets dark. Slightly fainter Saturn shines to the left low in the south.
The Perseid meteor shower, which I think of as the “Old Faithful” of meteor showers, will be partially washed out by a bright moon this year. You can probably see some if you watch for them Aug. 10 – 12 late at night.
The Great American Eclipse of the sun is happening Aug. 21 and if you cannot get down to Oregon to see it, there will be a partial eclipse up here. Not like the “Full Meal Deal” down there, but pretty cool nonetheless. Be sure to wear eye protection and enjoy!