Exposure: L 8×240 Bin 1, RGB 8×120 Bin2
Telescope: 10″ RC
Camera: QSI 683
Distance: 26,700 Light Years
Size: 14 Arc Minutes
Cluster Type: Globular Class IV
Messier 92 is a class IV globular cluster in the constellation Hercules. M92 is estimated at 14 billion years in age and thought to be the oldest globular cluster in the galaxy. This age estimate is partially based on the low metallicity counts in the stars of M92. Low metallicity indicates that the globular cluster was formed very early from gas and dust that was not yet enriched with metals.
M92 has 24 variable stars as of July 2012. [Christine Clement’s Catalog of variable stars in M92] Of these 17 are classified as RR Lyrae type variables. The other 7 are type SXP which is short for SX Phoenicis, a type of variable star with low metallicity and very short periods. M92 also has blue straggler stars with the heaviest concentration in the center of the cluster. A blue straggler star is a young hot star that is thought to have formed from an interaction with another star. During this interaction, the stars shed material and the cores merge to form a new star.
M92 will be within 1 degree of the North celestial pole in about 14,000 years. This will be the result of the Earths 25,772 year precession cycle.