This effort extends the Lowell Observatory Solar-Stellar Spectrograph (SSS) project, which has operated continuously since 1994. The SSS is a dual echelle spectrograph used for unique, long-term, synoptic observations of the Sun and Sun-like stars. In this project, the Principal Investigator (PI) will obtain observations of the Ca II H and K solar emission lines during the minimum of solar cycle 23/24, as well as make similar measurements for about 40 'solar analog' stars. These Ca II emission lines serve as proxies for solar and stellar chromospheric activity and can be used to study cyclical behavior. Secular trends in solar luminosity are best identified at cycle minima, and are critical for understanding long-term solar luminosity variations. These solar observations will allow the PI's team to make detailed comparison of emissions at successive solar minima, for comparisons with ongoing total solar irradiance (TSI) measurements.
For stars, such Ca II observations have provided direct observational evidence for stellar activity cycles, rotational modulation, and differential rotation. The PI's team has identified a set of about 40 'solar analog' stars that may provide critical clues regarding the behavior of stellar activity and luminosity. Studying these stars could provide insight into the Sun's past and future. By better characterizing the evolution of solar luminosity and that of the Sun's nearest stellar analogs, these observations may provide astrophysical insight into long-term solar activity and luminosity variations, and may also be useful for determining the likely level of solar influences on terrestrial climate change.
The PI's team will train Northern Arizona University students in solar and stellar observing and astronomical data analysis. The project will also involve a high school student in complementary observations of active binary stars as part of an accelerated research program operated by his school district. The PI will continue to disseminate his results online for broad public access, education, and participation. The PI's team will remain active in public outreach by offering presentations of their results throughout Arizona and the Southwest.
