出典:Wikipedia
出典:『Wikipedia』 (2011/06/21 15:27 UTC 版)
Messier 67 (also known as M67 or NGC 2682) is an open cluster in the constellation of Cancer. M67's Trumpler class is variously given as II 2 r, II 2 m, or II 3 r. It was discovered by Johann Gottfried Koehler in 1779. Age estimates for the cluster range between 3.2 and 5 billion years, with the most recent estimate (4 Gyr) implying stars in M67 are younger than the Sun. Distance estimates are likewise varied and typically range between 800-900 pc. Recent estimates of 855, 840, and 815 pc were established via binary star modelling and infrared color-magnitude diagram fitting, accordingly.