Title: Spinning Spots: Can We Diagnose the Properties of Starspots by Watching Them Rotate? A Test-of-Concept Using the Sun.
Type of Project: Data Analysis
Skills/Interest Required: Students that are interested in solar and stellar physics. IDL or other programming skills a plus.
Mentor: Dr. Steve Saar, Dr. Raphäelle Haywood
Understanding the effects of starspots on photometric and spectroscopic observations of Sun-like stars is not only very exciting for solar and stellar astronomers; it is also vital to study planets that orbit other stars than the Sun. Exoplanets are detected and characterized using photometric and spectroscopic
observations, and in this context, starspots are a source of "noise" and currently a major obstacle to studying Neptune- to Earth-size exoplanets.
The Sun is the only star whose surface we can resolve directly and at high resolution, so it is a unique test case to examine the impact of starspots, with the ultimate goal of interpreting
observations of other Sun-like stars. Sunspots typically consist
of a central umbra (dark, with a strong vertical magnetic field)
surrounded by a moat-like penumbra (brighter, with weaker, horizontal fields). The penumbra is characterized by a radial outflow called the Evershed flow. There is evidence that this flow affects the apparent net radial velocity (RV) of the integrated spot as it rotates across the disk. Similarly, many stars have
starspots, but little is known about their structure and properties. Can we diagnose these by studying their light and RV rotational phase curves? You will test this idea using solar data from the Solar Dynamics Observatory (SDO). Do stellar spots have penumbrae, and if so, how large and how cool are they? Just how
similar are sunspots and starspots anyway? Your work on solar data will pave the way to answering these questions. The results will improve our understanding of both stars and exoplanets.
Figure 1: An image of a sunspot from the Solar Dynamics Observatory, with the Earth for scale.