M3

From South Dublin Astronomical Society

M3
Type	Globular cluster
NGC	NGC 5272
Constellation	Canes Venatici
Right Ascension	13h 42.2m
Declination	+28° 23’
Magnitude	6.4
Size	16 arc min.
Image taken by Dave Grennan http://www.webtreatz.com/

A rewarding globular to track down in the Hunting Dogs is M3, shining with the light of a magnitude 6.2 star and thus visible to the naked eye under very good conditions. There is no nearby reference star to lead you straight to this stellar swarm but it lies roughly midway along a line joining Arcturus and Alpha (α) Canum Venaticorum. An alternative is to try “star hop” from magnitude 4.2 Beta (β) Comae Berenices — the cluster is 1½ times the standard five degree binocular field of 10x50mm instruments east of this star. M3 is some 33,900 light years distant — further than the Sun’s distance from the Galactic centre — and contains an estimated half a million stars. Some of these — the so called “Blue Stragglers” — appear much younger than the majority of the ancient suns in the globular. It is now believed that these stars have had their cooler outer layers stripped off through close stellar encounters as they wandered through, or near, the heavily populated core of the cluster.