How can we see the Milky Way if we are inside it? (Intermediate)

Hi! I was browsing through the website (great and interesting information by the way!), and I was wondering, how exactly are astronomers able to photograph the Milky Way if we are technically in it? Isn't it like trying to take a picture of the outside of your house while being IN your house? Thank you for your time!

It's more like trying to take a picture of the inside of your house while you are inside it, and while your house is cluttered with a bunch of junk to boot!

Because we are inside the Milky Way, we don't get to take any pictures of it from an angle "above" the Galaxy—for example, like this beautiful picture of M31, the Andromeda Galaxy. (However, we can make an educated guess as to what the Milky Way might look like from such an angle—for example, see this artist's illustration.)

Instead, we only get pictures in which we see the structure of the Milky Way edge-on, from inside of it. Examples of these pictures in many different wavelengths of light can be found here. Each picture is a panoramic photo—if you want an idea of what we really see, imagine taking each picture and wrapping it in a big circle around you. The photographer has simply chosen to "cut" and "unfold" this circle such that the Galactic Center (the brightest part of the Milky Way) is in the picture's center. This might give the illusion that we are looking at an edge-on picture of the Milky Way from the outside, but in reality we are not—the left and right edges of this picture simply represent material in the Milky Way that is located in the opposite direction of the Galactic Center from our point of view, and since we ourselves are pretty close to the edge of the Milky Way, there isn't much to see in this direction.

You can also see from these pictures how much "stuff" there is in the Milky Way which prevents us from seeing through to the opposite side. For example, the optical picture has a bunch of dark dust clouds that almost completely block our view of anything within the galaxy. Luckily, these dust clouds are much more transparent to other types of light (for example, infrared and radio) so we can use these wavelengths to look at objects on the other side of the galaxy from us.

This page was last updated June 27, 2015.

About the Author

Dave Rothstein

Dave is a former graduate student and postdoctoral researcher at Cornell who used infrared and X-ray observations and theoretical computer models to study accreting black holes in our Galaxy. He also did most of the development for the former version of the site.

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