092110

Recent years have seen great controversy about the rotational state ofsolar-mass stars older than the Sun. After excluding observational biasesevidence solidifies that the stars expected to rotate slower than the Sun arenowhere to be found leading to theories that such stars may have a mostlyswitched-off dynamo and continue to coast with practically constant rotationperiods into their future. However age-rotation studies can only detect adearth of stars rotating slower than our Sun not the reason behind it. Incontrast X-ray observations can probe the state of the magnetic dynamo andreveal whether a switch-off really occurs. We therefore propose deep X-rayobservations of a small decisive sample of old sunlike stars to find out the reason behind the missing slow rotators. [truncated! Please see actual data for full text]