In today's world, people often forget about the wonders of the night sky. Modern conveniences provided by civilization such as electricity and lighting result in light pollution that obscures our views. Pictures like the one below that I took near Champaign, Illinois show the yellow glow of city lights that reduces the contrast with the night sky and makes it difficult to see some of the more visually stunning, but lower contrast sights like the Milky Way. But you can still make out the Milky Way in my photo as a cloudy stripe that runs up from the southern horizon during summer in the Northern hemisphere, or winter if you are in the Southern hemisphere.
Many people may not realize that this fuzzy band is more than just an interesting cloudy feature in the night sky. When you look at the Milky Way, you are looking directly into our home galaxy. If you think of our galaxy as a fried egg, we are sitting about 2/3 of the way from the center, out in the white part. If you look toward the yolk, your view is obscured by all the intervening white between yourself and the center of the galaxy. Although the Milky Way is not made up of eggs, the analogy helps explain the basic shape of our galaxy. It has only been in the last few decades that we have finally been able to piece together our understanding of our own galactic neighborhood and our place in it. Modern methods of astronomy, including radio and infrared observations as well as precision measurements of stellar distances from space-based observatories, have helped us put a distance scale on our models. With a bit of Mathematica code and some NASA imagery, I have reconstructed a 3D picture of our place in the Milky Way galaxy.
To start with, I need a reference point. Modern astronomy has revealed that the center of our galaxy lies at or very near a radio source called Sagittarius A* ,which is approximately 25,000 light years away. I store the distance, right ascension, and declination of Sagittarius A* as follows. Right ascension and declination are sky coordinates that are like latitude and longitude on Earth, and I'll be using them as a reference coordinate system throughout this blog post.
