Experimental Physics I Final Presentation Galactic rotation curve and structure of the Milky Way.
SAARIK KALIA: OK. Hi. So my name is Saarik, and I'm going to be talking today about how we can use the 21 centimeter hydrogen line to determine the galactic rotation curve and some of the structure of the Milky Way galaxy. So first off, why do we care about galactic rotation curves? So basically rotation speed can tell us about mass. We know this from simple Newtonian mechanics. If you have a planet going around a sun, then its velocity is given by this equation, where M here is the mass of the sun. In our case, since we're working with a galaxy, we have spread out mass. This M is actually going to correspond to basically the mass contained within the orbit. So using a formula like this, given the mass distribution that we see in the Milky Way galaxy, we can guess what kinds of velocities we should see various things rotating at. And we can plot that and we get a curve that looks like this. But we actually, as we'll see later when we go ahead and observe what ...