When very massive stars (greater than eight times the mass of our sun) end their lives, they are thought to die in massive explosions known as supernovae. These stellar eruptions are incredibly energetic and luminous events, outshining entire galaxies in some ways. However, both theory and observation haven’t firmly answered the question of whether all massive stars die in such a way, or whether certain subsets of this mass range could do something more exotic. Measuring the mass of stars that have already exploded is quite difficult to do; essentially, we must get lucky and have already taken a picture of the star before it died. As a result, there are only roughly 25 such mass measurements that have been made in the entire supernova literature.
For my undergraduate research, I used an alternative method to make many more mass estimates. Rather than directly measuring the mass of a star that is no longer there, we measure the age of the surrounding stellar population, allowing us a very strong mass estimate of the star before it died. We applied this technique to a great deal of Hubble Space Telescope data taken of the Andromeda Galaxy and the Triangulum galaxy, both within the local galactic group. We were able to make 115 mass measurements of supernova progenitors using this technique, increasing the number of mass measurements in the literature by a factor of five and showing that at least some fraction of the massive star population in fact doesn’t die in a supernova explosion.