Katelin Schutz Theoretical Cosmologist & Foodie

The results? I found that there has to be dark matter in our galaxy because ordinary matter cannot account for the rotation speeds we see at large radii. Naively you would expect that based on where the stars are, the majority of stuff in the galaxy is concentrated at the center. However, that cannot be true and in fact my rotation curve is more consistent with a density that goes like the inverse of the radius squared. This proves that there is non-luminous matter in our galaxy! If I was ever skeptical of dark matter before, now I certainly have no reason to be. My conslusion is also consistent with my measurement of Oort’s constants. I was additionally able to use this technique to map out the spiral arms of our galaxy, which is pretty cool because you can’t just directly image them (fun fact: normally when you see “pictures” of the Milky Way, those are actually images of the nearby Andromeda galaxy.)

TL;DR: experimental astrophysics is hard, but very rewarding!

Proving Dark Matter Exists in our Galaxy and Mapping the Milky Way Spiral Arms

Even though this work is unpublished, I’m still pretty damn proud of it just because of the sheer amount of time I spent on it. This was done as part of MIT’s infamous Junior Lab, which very nearly killed me because it was so much work. Even though I’m a theorist, this class gave me a very healthy amount of respect for the challenges of carrying out an experiment and extracting physics in a meaningful, statistical way in the presence of systematic sources of uncertainty.

For this project, I used a radio telescope on the roof of MIT’s building 26 to observe the Milky Way. I spent over 40 hours observing over the course of two weeks (which I did on top of taking 2 physics classes in addition to other work for jlab and a music class!) I was able to use the 21 cm line of hydrogen (which is the result of a quantum spin flip transition) to figure out how fast the galaxy is rotating at different galactic radii. The way you figure this out is by using a combination of redshifting away from a wavelength of 21 cm as well as some clever geometry. The reason this is interesting is that the rotation speed at a given radius tells you about how much mass there is inside of that radius. In other words, the rotation curve can tell you how much matter there is in a way that is independent of how much light you observe from stars.