The globular cluster \Omega Centauri ( NGC 5139 ) is the most massive and brightest cluster in our Galaxy .
It has also a moderately high mass to light ratio ( 3.6 ) and an anomalous flattening ( 0.83 ) for a globular cluster .
This cluster is also very interesting because it is one of a few examples of globular clusters with a measurable spread in the metal abundance ( see Da Costa & Willumsen 1981 , Norris et al .
1996 , and Suntzeff and Kraft 1996 and references therein ) and then it offers a unique , big sample of nearby stars having all the same distance and reddening but showing different metallicity ( and age ? )
effects .
A recent paper by Norris et al .
( 1997 ) shows also an interesting correlation between kinematics and metal abundance .