What is the age of the closest star cluster in Ursa Major?
The famous Ursa Majoris ‘moving cluster’ is located about 75 light years away and occupies a space about 30 x 18 light years in projected space on the sky. In 1989, astronomer R. A. Proctor determined from proper motion studies that the five bright stars in the Big Dipper all were moving in a group through space. The stars, 17 in number, include Epsilon UMA, Beta UMA, Zet UMA, Gamma UMA, Delta UMA, and even Alpha Corona Borealis! It is moving at a velocity of about 9 miles per second towards a point in Sagittarius near 20h 24m and – 37degrees. The cluster contains mainly main sequence stars from A0 to K3, and its age is many tens of millions of years at least although I have no detailed reference for the actual age available to me.
