If you have not had a chance to check out the Milky Way arcing across the night sky, September is perfect for spotting this majestic sight. First, find yourself a dark place with no extraneous lights to ruin your night vision. Out in the country away from town would be ideal. Also, you will want a moonless sky. The later part of August until early September and then again from about Sept. 17 until early October will be great for moonless nights in the early evening.
Use the two bright planets, Jupiter and Saturn, as guides to find the Milky Way. Look south for the planets. Jupiter will be the brighter one on the right and Saturn, the dimmer of the two on the left.
After you have let your eyes adjust to the darkness, you should be able to see a hazy glow of light between the planets. Follow it up almost overhead and into the north. If you see it, congratulations! Most of the world has lost this view of our home galaxy due to light pollution.
Down low in the south we are looking at the center of our galaxy, a central bulge in a huge pinwheel-shaped structure. The glow extending into the north is one of two spiral arms spinning out of the center.
Every star you can see in the sky calls the Milky Way home, including the sun. Our home star is traveling through this pinwheel at 500,000 miles an hour and it tugs the earth and all the other planets along with it. Imagine that we and all the stars are riding on a giant merry-go-round through the galaxy. It takes us about 250 million years to make one trip around it but not because we are pokey, but simply because it is so big.
If you could fast forward 100 years and step out again to look at the stars, they will not have changed one bit in their relative positions to one another. Fast forward 1,000 years and still there would be no change. Fast forward 1 million years and some of the constellations would be distorted. Finally, we can see the movement of the stars through the galaxy. You would think that at 500,000 miles an hour that we would see things flying around out there, but the distances are too vast and our lives too short for us to notice.
Merry-go-rounds usually have a few ponies to ride on that bob up and down as they go around. Our sun bobs too as it cruises through the cosmos, bobbing up and down through the galactic plane or the center line of that pinwheel. It takes about 60-some million years to make one bob and about 3 million years ago we were cutting right down through that edge on plane. It is difficult for us to understand time frames like this but suffice it to say that entire geological periods have passed by in a single bob on that giant merry go round.
If you think about it at all, you might assume that when you arrive at your birthday each year, you have made one trip around the sun and now you are back where you started from a year ago. Actually because of the sun’s motion through the galaxy, you have traveled about 4,380,000,000 miles through the galaxy in that year That is about as far away as Pluto.
Because we orbit the sun, think of the earth’s motion through the galaxy as a spiraling helix, spinning around and around through space, cruising along at 500,000 miles an hour. It is enough to make you dizzy!
If that is not enough for you, I will throw in one more motion. Have you ever heard of the Andromeda Galaxy? It is the closest big galaxy to us, actually quite a bit larger than our own Milky Way. Do not let the word closest fool you. It is really a long, long ways away. Our entire galaxy including every star we see in the sky and the earth too are falling into that behemoth. Probably not in a straight line but in a kind of a death spiral and it is all because of our old friend gravity, the same force that lets you collapse on the couch after a hard day of work.
October will be a great time to see the Andromeda Galaxy and it can be spotted with the naked eye. By the way, we are going to crash, but you do not have to rush right out and buy collision insurance just yet.