Looking Out Into the Heart of our Galaxy
Look out into the night sky far away from city lights and air pollution, and the chances you are you will see part of the Milky Way stretching across the sky. What you are seeing is the view of our galaxy from the inside. Our galaxy, like many others, is a spiral. Hundreds of billions of stars, slowly spinning around a huge bulging center.
Our sun is, in the words of The Hitchhikers Guide to the Galaxy, "at the unfashionable end" of one of those spirals, and as we look out at the Milky Way, we are looking across the disk of the galaxy. We are seeing it end-on, from the inside.
Looking at the Milky Way near the constellation of Sagittarius, the broad part of the Milky Way that is in the South in the Summer (for Northern Hemisphere observers), moving into the West in the Autumn, you are looking straight into the center of the galaxy.
These clouds of stars, the spirals of our own galaxy, are the farthest we ever see with the naked eye. Beyond them, we now know, are other galaxies, billions upon billions of them. But everything we see in the night sky is a star within our own galaxy (or a planet in our local solar system). And the brighter stars in the sky, those that mark the constellations, are, by and large, the ones closer to us. From across the galaxy these many individual stars are but a tiny part of someone elses view of the Milky Way.
The next time you look into the night sky, see it as a three-dimensional view of our galaxy from the inside. Visualize the cloud of stars forming the Milky Way, as the huge spiral disk of stars in which we are embedded, slowly spinning in space -- going round once every 200 million years, or so. Shining all around us are thousands of other stars -- the ones closest to us, shining the brightest.