Messier 92 (M92)

Also Known as: NGC 6341

Object Type: Globular Cluster

Constellation: Hercules

Distance from Earth: 26,700 light years

Apparent Magnitude: 6.3

Coordinates: RA 17H 17M 07.39S DEC 43 deg 08 min 09.4 sec

Actual Size: 108,000 light years in diameter

Apparent Dimensions: 14 arc-minutes

Discovered by: Messier 92 was discovered by the German astronomer Johann Elert Bode on December 27, 1777. Bode described the object as a “nebula. More or less round with pale glow.”.
Charles Messier independently discovered the cluster and catalogued it on March 18, 1781, along with eight galaxies in the Virgo Cluster: Messier 84, Messier 85, Messier 86, Messier 87 (Virgo A), Messier 88, Messier 89, Messier 90 and Messier 91. The galaxies are located in the constellations Virgo and Coma Berenices.

Description: Messier 92 is one of the brighter northern globulars – both visually and in terms of absolute magnitude – and can be seen without binoculars under good conditions.
It is, however, not as popular a target for amateur astronomers as the brighter and larger Hercules Globular Cluster (M13), which lies in the vicinity.
M92 has a much denser core and is more difficult to resolve than M13.
M92 contains about 250,000 stars with an estimated mass of 330,000 solar masses. The cluster is approaching at 112 km/s.
With an estimated age of 14.2 billion years – almost the same age as the universe itself – M92 is one of the oldest clusters known and possibly the single oldest globular in the Milky Way.
The cluster has an extremely low abundance of elements other than hydrogen and helium, with only 0.5 percent of the Sun’s metallicity.
The cluster is located 16,000 light years above the galactic plane and 33,000 light years from the galactic center.
Messier 92 is classified as an Oosterhoff type II (OoII) globular cluster, which means that it is a metal poor cluster with longer period variable stars of the RR Lyrae type.
It contains 28 candidate variables, of which 20 have been confirmed.
These include 17 RR Lyrae variables and a W Ursae Majoris type variable, an eclipsing binary star whose two components share an envelope of material and are in contact with one another.
The north celestial pole will come within a degree of M92 in about 14,000 years. Every 26,000 years, the Earth completes a precession of its axis and, during that cycle, the pole moves near M92. M92 was last a pole cluster back in 10,000 B.C.
Currently, the pole is pointing toward Polaris, Alpha Ursae Minoris, the brightest star in Ursa Minor constellation.

Click Below Image(s) for Full Size:

With 10x50 binoculars, M92 appears as a blurry star with a bright core.
Small and medium sized telescopes resolve some of the stars in the outer regions of the cluster. 6 and 8-inch scopes show and oval-shaped cluster with bright center surrounded by a halo of stars.

The best time to observe M92 is during the summer months of June-August when Hercules is high overhead in the evening for northern observers.

Platesolve

M92 Globular Cluster

Imaging Details
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