Cosmic Chemical Evolution
Truran, J. W. / Nomoto, K.![Cosmic Chemical Evolution](https://support.digitalhusky.com/media/annotations/sorted/178/1786556/CHSBZCOP031786556.jpg)
The open cluster NGC 6791 is now considered both the oldest and the most metal-rich known. Its age is 8 -10 Gyrs, twice as old as the canonical solar-metallicity cluster M67 (Garnavich et al. 1994, Demarque, Green, & Guenther 1992, Tripicco et al. 1995). That its metallicity is significantly above solar is suggested from moderate-resolution spectroscopy and from a mismatch of its color-magnitude diagram (CMD) with solar-metallicity isochrones....