This program will perform a detailed spectroscopic study of the 19th century Great Eruption of the famous eruptive massive star Eta Carinae, by targeting light echoes discovered 160 years after the outburst occurred. Eta Carinae is the prototype for a class of non-terminal eruptions that dominate mass loss in massive stars and have been linked to violent pre-supernova ejections that yield the most luminous supernovae in the universe. Our empirical information about its eruption has been limited to historical accounts of its visual brightness, since the astronomical spectrograph had not yet been invented when the eruption occurred. However, our recent discovery of light echoes from Eta Carinae provides a unique opportunity to get a second look with modern instruments, because light from the 19th century eruption bounced off nearby dust clouds in the surrounding star-forming region, reaching us now. By observing the multiple light echoes we have discovered, we will produce a detailed spectral time-sequence of the 20-yr long 19th century eruption of Eta Carinae, including brief brightening events, quiescent times before and between peaks, and long-duration bright phases. Understanding the 3D effects in Eta Carinae will help us model extragalactic events where we lack any spatially resolved information about geometry. We will directly test and refine theories for the eruption that involve non-terminal explosions and dense continuum-driven winds above the Eddington limit. This study is also quite timely: It will inform a rapidly-growing interest in eruptive transient sources fueled by current transient surveys and anticipation of LSST, it will provide important clues to the eruptions from very massive stars that precede the most luminous supernovae known (in advance of JWST's efforts to detect them at high redshift), and it will provide direct tests of some very recently proposed models for the eruption of Eta Carinae itself.
There are several aspects to the broad scientific impact of this program. It will provide unique and timely information about a famous massive star and its historical event that is a benchmark for understanding transient phenomena in the universe, eruptions and explosions associated with non-terminal transient events, and their role in the lives and deaths of stars. Aided by professional graphics and animations generated with the help of the STScI public outreach department, we will also produce a series of YouTube videos of team members explaining key aspects of the project for a non-specialist audience. Concerning traditionally underrepresented groups in astronomy, through participation in the NSF-funded CAMPARE exchange program between Arizona and Cal-Poly Pomona, we will recruit minority undergraduates to be directly engaged in the research, and the Arizona graduate student intended to be funded by this grant is female.
