Quirks & Quarks

Where exactly are we in the Milky Way Galaxy?

We're in one of the spiral arms of the Milky Way galaxy, so when we look at it from Earth, we're seeing the centre
Photograph of Milky Way galaxy taken from Earth. (Serge Brunier/Nasa.gov)

This week's question come from Ryan Sauve from Calgary, who asks "Regarding those long exposure photographs we see of the Milky Way Galaxy, what part are we looking at, and where exactly are we in the galaxy?   

Dr. Rachel Alexandroff, a Postdoctoral Fellow at the Dunlap Institute for Astronomy and Astrophysics and the Canadian Institute for Theoretical Astrophysics describes the Milky Way as a spiral disc that is much wider than it is thick. In fact it is about 100,000 light-years across, but only 1000 light-years thick.

When we see images of the Milky Way, from our position in the galaxy, we can look toward the centre, which appears to us as the thicker part, and we can also see the outskirts, which is the thinner part at the edges. Our position in the Milky Way here on Earth is about 25,000 light-years from the centre in one of the galaxy's minor arms, called the Orion Spur. Some would say we are in the suburbs of the galaxy. 

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