The Sun-like Activity of the Solar Twin 18 Scorpii

Abstract

We present the results of 10 yr of complementary spectroscopic andphotometric observations of the solar twin 18 Scorpii. We show that overthe course of its ~7 yr chromospheric activity cycle, 18 Sco'sbrightness varies in the same manner as the Sun's and with a likelytotal brightness variation of 0.09%, similar to the 0.1% decadalvariation in the total solar irradiance.