I am in Astr. 1020, and in my introductory Astronomy class I had last semester, we didnt learn anything. It was a "here's the study guide (aka the answers to the test)" kind of class so I didnt really learn that much. Now, my Astr. 1020 teacher is rather difficult due to what I didnt learn last semester... So on to the problem. For homework we have to find the density of Stars. It should be hard, mass (g) divided by volume (of a sphere, cm^3), I understand that much. In the problems, we are given everything relative to the sun (I hope I'm stating that correctly). So, the data we have for the sun is 1.0m(sun) and 1.0R(sun). How am I supposed to do this and get g/cm^3? I'm thinking, for example, Sirius (which is 2.0m(sun) and 2.0R(sun)) and multiply that by the mass and the radius of the sun, respectively. Is that right? Thanks for the help, guys!