The Fates of Stars
The vast majority of stars end their lives in one of two ways. Some stars explode as supernovae, leaving behind either a neutron star or a black hole, while most stars lose their mass more gently and form white dwarfs. The criterion determining the fate of a star is thought to be its mass; more massive stars go supernova, while lower mass stars form white dwarfs. However, the value of this critical mass is uncertain, lying somewhere between 6 and 10 solar masses. Assuming standard stellar mass functions, a burst of star formation will produce as many stars in this uncertain range as it will stars of higher mass, meaning that the number of supernovae resulting from that burst of star formation is uncertain by a factor of two. Since supernovae are a major source of many metals and since they inject a lot of energy into the interstellar medium, it is important to better constrain the mass dividing white dwarf and supernova progenitors.
My research uses white dwarfs as astrophysical probes of the fates of stars. At its simplest, stars that form white dwarfs did not explode as core-collapse supernovae. So, if I can determine which masses of stars make white dwarfs, I can infer which masses of stars go supernova.
More specifically, I use white dwarfs in open star clusters to constrain this crucial dividing line. Since open star clusters are simple stellar populations, we know the age and metallicity of each star, including the white dwarfs. These constraints allow us to determine the masses of each white dwarf's progenitor star. Based on the work of my collaborators and myself, we can confidently claim that stars less massive than about 6.5 solar masses form white dwarfs. I am now expanding this work to more star clusters to try and constrain this dividing line further.