The galactic cluster M 67 and its significance for stellar evolution.
Abstract
Colors and magnitudes on the U, B, V system have been determined for nearly 500 stars in the galactic cluster M67. The color-magnitude diagram is unlike that of any other galactic cluster known. The apparent modulus is m - M = 9.70 + 0.1, as determined by a fit of the main sequence to the C-M diagram of the near-by stars. M67 may be the oldest galactic cluster known. Its age is approximately 5 X 10 years. Comparison of the M67 diagram with the globular clusters M3 and M92 suggests the effect that chemical composition may have upon the paths of evolution for individual stars in the C-M diagram. Comparison of the M67 diagram with other galactic clusters illustrates the effect that mass differences may have on the tracks of evolution. A prediction is made, on the basis of the general trend of C-M diagrams for galactic clusters, that giant stars in the general field at M,, 0.0 near K0 may have a range of mass from about 1.2 to 3.0 o. Data from the M67 diagram, together with evidence for a lack of subgiants of luminosity class lv later than K2, suggests that there were no stars in existence near the solar neighborhood more than about 5 X 10 years ago.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- May 1955
- DOI:
- 10.1086/146027
- Bibcode:
- 1955ApJ...121..616J