Resolving the Inner Winds of Massive Stars

Astronomers usually see stars as tiny points of light because they are so far away. To study them in greater detail, the CHARA Array combines multiple telescopes to act like one giant telescope. CHARA is operated by the Georgia State University's Center for High Angular Resolution Astronomy at Mount Wilson Observatory in California. Two new upgrades, a visible light instrument, called SPICA and a movable seventh telescope called CMAP, greatly improve the array's ability to observe distant, massive stars. The project will use these new tools to study the powerful stellar winds that cause massive stars to lose large amounts of material over time. By comparing observations at different wavelengths, researchers can measure how quickly these stars lose mass and how their winds change over time. These observations will improve our understanding of stellar atmospheres, the evolution of massive stars, the types of supernovae they produce, and whether they eventually become neutron stars or black holes. The CHARA Array is playing a key role in advancing high angular resolution astronomy and making the facility available to the entire community through an open access program. This observational program is designed to obtain measurements over timescales of days to years in order to study the intrinsic variability of the stellar winds. Together with independent distance estimates, the CHARA observations will provide accurate stellar radii and test current models of the temperatures and gas properties in the stellar atmospheres. The observations will document the kinds of wind variations that are related to stellar rotation and to the formation of shocked gas structures. This program will also provide training opportunities for young scientists and will share these explorations of the cosmos with a wide public audience. A postdoctoral associate will develop considerable expertise in electro-optical systems, software for instrument control and data analysis, and research at the frontier of angular resolution. Doctoral students from Georgia State University and elsewhere will use the CMAP instrument for their dissertation research. Undergraduate students from local colleges will work during summer months with CHARA staff. The Mount Wilson Observatory is a destination for 100,000 visitors each year, and this proposal will support staffing in the Exhibit Hall to increase public awareness, along with regular release of short videos to the public explaining the advances made by the project. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.