Planets in External Galaxies by Rosanne Di Stefano
Prior to the discovery of exoplanets, it was widely conjectured that the Milky Way contains planetary systems in addition to the Solar System. The discovery of exoplanets in the early 1990s, however, opened a new discovery space. We are now able to study planetary systems with constituents and architectures far different from those of our Solar system. It seems highly likely that external galaxies are also rich in planetary systems. I will discuss the search for and discovery of the first candidate planet in an external galaxy, M51. The planet candidate has a size most likely comparable to that of Saturn, and is in a wide orbit. The discovery was made through the study of signatures of transits of the X-ray emitting regions of X-ray binaries. We discuss the implications for planetary studies, including possible extensions of this work to X-ray binaries in additional galaxies and in the Milky Way.
Rosanne Di Stefano is a Senior Astrophysicist at the Harvard-Smithsonian Center for Astrophysics. Her thesis work was on Hamiltonian dynamics and supersymmetry, but she has been researching questions in astronomy since the early 1990s, first at MIT, then at Harvard and SAO. Her current professional interests are on binaries and triple systems, particularly topics related to the progenitors of Type Ia supernovae, gravitational mergers, and binary self-lensing. She has conducted studies of both newly collected and archived X-ray data and is engaged in time series analysis for both X-ray and optical events, including microlensing. She is a member of the Vera Rubin Observatory's team on transients.