When the bright moon is not in the sky, the dark summer night reveals one of its most spectacular treasures — the soft, misty glow of the Via Lactea, or the Milky Way.
Contrary to what the ancient Romans thought, the Milky Way is not made of milk but is the combined light of billions of distant suns, unresolved by the unaided eye.
If you look through a pair of binoculars and sweep slowly across the Milky Way, you will rediscover what Galileo did in 1610 — a multitude of faint stars. The situation is similar to flying high over a sandy beach and seeing the white sand stretch for miles in both directions and, yet, you cannot see the individual sand grains that make up the beach from that height. In this case, the grains of sand are the stars that populate the Milky Way. Our sun is but one grain of sand on this cosmic beach.
The Milky Way is our home galaxy, a spiraling collection of hundreds of billions of stars, more or less like our sun. The word “galaxy” literally means “milk,” from the Greek word “galax.” Because it is flattened like a pancake, and we peer outward from within that pancake, we see the Milky Way wrapped gently around us in a narrow band that runs almost north to south on summer evenings.
One of the brightest portions of the Milky Way is seen just above the spout of the Teapot asterism of Sagittarius. When we peer off into this direction, we are looking directly toward the center of the Milky Way galaxy, some 28,000 light-years away. We cannot view the center directly because of the intervening stars, gas and dust, but there is mounting evidence that a supermassive black hole lurks there, at the heart of our galaxy.
Experiencing the subtle beauty of the Milky Way has become a privilege that many Americans might never have. A large percentage of our nation’s population lives in or near a large city where human light pollution drowns out this natural wonder. To them, the Milky Way is something that you see pictures of in a book or see a fake version of in a planetarium. Streetlights and spotlights aimed skyward scatter so much unnecessary light into the night sky that it overwhelms all but the brightest stars. Many cities are making efforts to curb this urban light pollution to preserve the beauty of the night sky.
For the time being, at least, here in northwestern Colorado, all we have to do is step out into our backyard to see the galaxy of which we are part of, the magnificent Milky Way.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College’s Alpine Campus. His “Celestial News” column appears weekly in the Steamboat Today newspaper and his “Cosmic Moment” radio spots can be heard on local radio station KFMU. Check out Westlake’s astrophotography website at www.jwestlake.com.