M67 is one of the oldest known open clusters, and with age of 3.2 billio years far the oldest of Messier's open clusters.

This is still less than the age of our Solar System, but open clusters usually get destructed much faster.
The total number of stars in M67 is probably at least about 500. Brightest stars are blue subigants and have apparent magnitude of 10.

According to Johann Elert Bode, M67 has been discovered by Johann Gottfried Koehler (1745-1801) somewhen before 1779; it seems, however, that Koehler's instruments were so inferior that he couldn't resolve this cluster. Charles Messier independently rediscovered M67, resolved it into stars, and cataloged it on April 6, 1780.