The massive open cluster M67 has been found to have a chemical composition close to solar, and an age of about 3 Gyears. It offers an important opportuinity to check our understanding of the physics and the evolution of solar-type stars. We present the first high resolution, R~50,000, study of the potentially best solar twin in the cluster identified among solar-like cluster stars.
At $V \approx$ 15, G dwarfs in M67 ($d \approx$ 900 pc) are relatively faint which made spectroscopic studies a time consuming undertaking. Using the multi-object spectrograph GIRAFFE on the VLT, Pasquini et al. (2008) have recently observed solar-twin candidates in M67 at medium resolution. In this talk, we present results of a follow-up study using FLAMES-UVES discussing chemical-abundance similarities and differences between the M67 solar twin and the sun.
Working with a solar twin, we minimize systematic errors in the abundance analysis compared to previous studies that utilized more evolved stars to determine the metallicity of M67. A strictly differential approach yields accurate and precise abundances for M67, which sharpens the possibilities to use this object to empirically constrain the future evolution of the sun.