The Milky Way – Observing our home in the universe

By Chris Fellows, Serenity Mobile Observatory

July is here and everyone is out in the parks grilling hot dogs and splashing in the waters all around our beautiful country. I am parked and have my scope set up in a family-oriented park in northern Michigan. Every weekend a new group of campers comes in with all the wide-eyed kids that are curious about the “big telescope guy” out on the point. So naturally, I set out my whiteboard and invite everyone to come over after sunset to get a look through the eyepiece.

This summer is great because there are no less than five planets in the sky over the course of the night. They march in a parade: from Mercury just at sunset, to Venus, Jupiter, Saturn and finally Mars across the sky, over the course of the evening. The planets are great crowd-pleasers so we mostly stick to them. But last weekend, one boy, maybe 7 or 8 years old, made an observation that changed the narrative for the whole night.  

The Milky Way in summer. Click to enlarge.

We are in a fairly dark area here but it’s not extremely dark. I am camped just about 6 miles outside of Alpena, Michigan, a town of about 30,000 to the east of my campsite. There are also several other small towns in a 50-mile radius that, in the dead of night, you can see the light domes on the horizon in several directions. The point I am trying to make here is that you don’t have to be in a National Dark Sky location to make this observation on your own. As long as you aren’t in the middle of a large city you may be able to see it, with your naked eyes, wherever you happen to be.

Anyway, back to the kid with the sharp eyes. We were looking at Saturn in Sagittarius and the air had gotten a little unsteady, so the view was fuzzy and bouncing around as the atmosphere distorted the light coming from the ringed planet. This boy pulled back from the eyepiece and said, “I wish it wasn’t so cloudy.” Confused, I quickly looked up and it was a perfectly clear night, so I asked him what he was talking about. He pointed up and said that cloud is making it hard to see Saturn. I followed his gaze and he was pointing at the Milky Way.

I knew this was a teaching moment, so I gathered the rest of the group, maybe a dozen people of various ages, pointed up at the sky and asked what they thought that line of light that stretched from horizon to horizon was. To a person, they all thought it was a cloud. For the rest of the evening we all talked about our galaxy, our cosmic town in the vastness of the universe. It was fantastic. I immediately thought of all of you and how you may not have realized that with your naked eyes (and maybe a small pair of binoculars) you can see, even from a not particularly dark location, the splendor of our cosmic neighborhood called the Milky Way.

Our location in the Galaxy. NASA image. Click to enlarge.

We are, of course, embedded inside the Milky Way. The sun travels around the galactic core, about halfway out from the center, in what is known as the Orion Spur, spiral arm of our galaxy. Being inside of something makes it pretty difficult to get an idea about that something’s shape and size.

Think about it this way, in your mind’s eye, take a walk into a dense forest that you are unfamiliar with and have no maps of. Find a small clearing and sit down – you can’t move from this location. Now, try to draw the entire forest on a sheet of paper. It’s going to be tough, but not impossible especially if I give you a couple of tools.

First I am going to allow you a good pair of binoculars that you can scan the forest with. I am also going to give you a special device that makes the leaves on the trees basically transparent when you attach it to your binoculars. And lastly, but maybe most importantly, I am going to say that if you look up, or down (in my analogy the ground is transparent also), you will see billions of separate forests that you can use as guides to figuring out the nature of the forest you are sitting in. With these things in hand and given enough time you will be able to get a pretty accurate picture on your paper.

This is very analogous to the situation we find ourselves in here on Earth. We use our telescopes to look at the forest of stars, gas and dust that surrounds us, we use the entire electromagnetic spectrum (infrared through Gama ray) to see through the dust and gas clouds, and we use the billions of other galaxies visible in the night sky as a guide to how nature forms star systems. Using these tools and over a couple of centuries of compounding human knowledge, we have developed the following picture of our cosmic home.

Chris Fellows’ image of M51, another spiral galaxy like the Milky Way. Click to enlarge.

The Milky Way is a fairly large galaxy – not huge by universal standards but not tiny either. It contains somewhere between 100 billion to 400 billion stars, large amounts of interstellar gas and dust that create stellar nurseries and give birth to new stars, and a super massive black hole, called Sagittarius A* (pronounced “Sagittarius A-star”), of about 4 million solar masses that binds the whole thing together and eats up anything that gets too close, including light.

The galactic disk, and it is a disk because we are of a galactic type called a barred spiral, is about 100,000 light years across and about 2,000 light years thick. It is really a very thin disk with a 50/1 ratio. We sit within the disk about 26,000 light years from the core and Sag A*. The galaxy is rotating, spinning like a top, and it takes about 240 million years to make a single turn on this merry-go-round. The last time the sun was in this position relative to the core Earth was in it’s Triassic period and great dinosaurs ruled the world.

This is getting a little long so I think I will wrap it up here. But get out a lawn chair and a favored beverage, turn off all the lights that you can and just lay back this summer and look up at the night sky. If the conditions are right, you will be able to see the splendor of the Milky Way stretching from horizon to horizon with your own eyes and wonder at our place in the universe.

Till next time!

Clear Skies,
Chris Fellows, Serenity Mobile Observatory

Find Chris on Facebook (or, if you’re lucky, at your campground). (Editor: Check out his amazing photos on his Facebook page!)

 ##RVT853

Related

2 Thoughts to “The Milky Way – Observing our home in the universe”

  1. marty chambers

    One item on my bucket list is to truly see the Milky Way from a location with no light pollution. Thanks for your articles.

    1. Serenity Mobile Observatory

      I’m glad you enjoyed it Marty. Get yourself to a dark sky location and check this one off!

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.