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M.S. Giampapa (NSO/NOAO), R.R. Radick (AFGL), S.L. Baliunas (SAO)
The results of our program to survey the level of chromospheric Ca II H&K emission in ~ 100 solar analogs in the galactic cluster M67 are discussed. This cluster is an appropriate target of observation for the study of solar-type stars since it is approximately the same age and has the same chemical composition as the Sun. The key objective of our program is to investigate the nature of solar variability. In particular, we interpret the range of Ca II H&K emission observed in the sun-like stars in M67 as indicative of the possible amplitudes of cycle-related variability that can occur in the Sun itself. In this way, we can efficiently gain insights on the potential long-term variability of the Sun that would not otherwise be possible with the modern solar Ca II synoptic database of just a few decades. This is especially important given that the amplitude of long-term solar (and stellar) variations in brightness are correlated with cycle variations in chromospheric emission. In view of the fact that the Sun is the engine that drives climate on the Earth, any variation in the solar ``constant" must be taken into account in the study of the long-term behavior of the global climate.
The NOAO is operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation.
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