Research

I study stellar rotation and magnetic activity to understand how stars evolve.

All stars rotate, including the Sun, which spins on its axis once every 25 days. Rotation can deform stars and cause extra chemical mixing, affecting their structure and evolution. Because stars are giant balls of highly charged gas, their rotation generates strong magnetic fields, which can also affect their evolution as well as the environments around them. Magnetism in the Sun causes space weather, including energetic ejections of charged material that could knock out the Earth's power grid. Understanding how stars rotate is critical to understanding the evolution of stars and the habitability of planets around them.

We can study the rotation of stars in a number of ways, one of which is by measuring the changes in brightness caused when starspots (like sunspots) rotate into and out of view, periodically dimming and brightening the star as seen from Earth. A series of brightness measurements is called a light curve, and they are most easily recorded by telescopes in space.

I measure the rotation of tens of thousands of stars by analyzing their light curves as recorded by the NASA Kepler, TESS, and soon Roman missions. These missions were all designed to discover new planets outside our Solar System, which requires long stares at the sky looking for changes in brightness as planets eclipse or magnify light from their host stars. These long stares are also perfect for obtaining rotation-worthy light curves.

My active research uses machine-learning techniques to measure rotation from stellar light curves and gyrochronology to estimate stellar ages from rotation periods. I develop and maintain open-source software packages to power these investigations. See the Software page for more details, including how to get involved.