hydrogen (H), and potassium (K) flux as an indicator of chromospheric activity, or by photometric observations of solar cycles on decadal timescales. Early estimates of grand minimum frequency in solar-type stars ranged from 10 to 30 percent. However, these early studies inadvertently included many stars that have evolved off the main sequence. More recently, Hipparcos parallax measurements have yielded reliable differentiation between true main sequence stars and slightly evolved stars. In addition, measurements of stellar lithium abundance, and spectroscopically derived metallicity, can provide additional constraints on age and help refine detections of grand minimum analogs in solar-type stars. At the same time, some evidence suggests that instantaneous Ca, H, and K flux measurements alone may be unsuitable for detecting grand minimum analog candidates: at least one plausible candidate has been identified in time series data including a flat activity cycle but with chromospheric activity greater than present-day solar activity. Based on the most recent studies, an estimate emerges in the range of 5 to 6 percent for the fraction of the Sun’s lifetime spent in a low-activity and reduced-luminosity state analogous to the Maunder Minimum.



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