Messier 15 (M15)

Common Name: Great Pegasus Cluster

Also Known as: NGC 7078, GCI 120

Object Type: Globular Cluster

Constellation: Pegasus

Distance from Earth: 33,600 Light years

Apparent Magnitude: 6.2

Coordinates: RA 21H 29M 58.33S DEC 12 deg 10 min 0.12 sec

Actual Size: 175 light years in diameter.

Apparent Dimensions: 18 arc minutes.

Discovered by: Messier 15 was discovered by the Italian astronomer Jean-Dominique Maraldi on September 7, 1746. Maraldi stumbled upon the cluster while searching for a comet and described it as a “fairly bright nebulous star, which is composed of many stars.”
Charles Messier included it in his catalog in 1764 believing it was a nebula. It was William Herschel who finally resolved the cluster into individual stars in 1783.

Description: Messier 15 is one of the oldest known globulars in our galaxy. It has an estimated age of 12 billion years and only 1 percent of the Sun’s iron content.
Messier 15 has a density classification IV and is one of the most densely concentrated clusters of its kind. The central density cusp is a result of the cluster having undergone a core collapse, a contraction of its core region.
This is a common occurrence in globular clusters as they evolve.
The cluster is notable for its steep central cusp, with an exceptionally large number of stars orbiting what is likely a central black hole.
The cluster has an absolute magnitude of -9.2, which makes it about 360,000 times more luminous than the Sun. It has an apparent diameter of 18 arc minutes. It is one the most densely populated clusters.
The core of Messier 15 is very small – about 0.14 arc minutes or 1.4 light years – compared to the cluster’s size.
Half the cluster’s mass is concentrated within the central 10 light years, or 1.06 arc minutes.
Scientists have theorized that either the cluster contains a supermassive black hole at its core or the concentration of mass is a result of the gravitational interaction of the stars in this area.
A survey of the cluster’s inner 22 light years alone revealed about 30,000 stars. M15 contains more than 100,000 stars and is approaching us at 107 km/s.

Click Below Image(s) for Full Size:

Messier 15 can easily be seen in binoculars and small telescopes, but only appears as a fuzzy patch of light in smaller instruments. The cluster’s stars can be resolved by 6-inch and larger telescopes. Amateur telescopes will reveal an object about 7 arc minutes in size visually.

M15 is best viewed in the summer months.

Platesolve

M15 Globular Cluster imaged with SVX130 refractor

Imaging Details

M15 Globular Cluster imaged with Celestron 11 inch SCT

Imaging Details
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