Messier 15 – M15 - Globular Cluster

M15 is one of the brightest and finest globular clusters in the northern section of the sky and the best deep-sky object in the constellation of Pegasus. It is only marginally fainter and smaller than M13, the finest northern globular cluster. M15 is relatively easy to find, located 4 degrees to the northwest of magnitude +2.4 star Enif (Epsilon Pegasi - e Pegasi) and positioned on one edge of a right-angled triangle made up of stars of 6th, 7th and 8th magnitudes.

M15 Globular Cluster (NASA, ESA, and The Hubble Heritage Team (STScI/AURA))

Finder Chart for M15

Finder Chart for M15 - pdf format

Finder Chart for M2 (also shown M15)

Finder Chart for M2 (also shown M15) - pdf format

Approaching naked eye visibility under excellent conditions, this globular cluster is easily observed with binoculars or finder scopes, appearing as a magnitude +6.2 fuzzy star. A 100mm (4-inch) telescope at low power (40x) reveals a uniformly lit disk while high powers (>100x) hint at resolution of some of the outer stars. When viewed through a larger 200mm (8-inch) telescope, M15 appears as a large bright diffuse ball surrounding a dense compact centre region, with many individual stars resolved in the outer halo. The brightest of these stars are of magnitude +12.6. Larger telescopes do even better. A 300mm (12-inch) scope resolves many stars across the complete disk, creating a spectacular 3-dimensional effect. In total, the globular has an apparent diameter of 18 arc minutes, however in amateur telescopes it appears somewhat smaller, perhaps only 8 arc minutes visually.

M15 is one of the most densely packed globulars known in the Milky Way galaxy. Its core has undergone a contraction known as "core collapse" resulting in an enormous number of stars surrounding what may be a central black hole. It is also unusual in that it is one of only four known globulars (along with M22, NGC 6441 and Palomar 6) that contains a planetary nebula. The planetary nebula is named Pease 1.

The cluster was discovered by Italian born French astronomer Jean-Dominique Maraldi on September 7, 1746 and is located 33,600 light-years from Earth. With an age of at least 12.0 billion years, it's thought to be one of the oldest known Milky Way globular clusters.

M15 Data Table

Messier15
NGC7078
Object TypeGlobular Cluster
ConstellationPegasus
Distance (kly)33.6
Apparent Mag.6.2
RA (J2000)21h 29m 58s
DEC (J2000)12d 10m 00s
Apparent Size (arcmins)18 x 18
Radius (light years)88
Age (years)12000M

Sky Highlights - July 2016

Mercury, Venus and Jupiter
Mercury, Venus and Jupiter visible together in the evening sky from southern and tropical latitudes from July until September 2016

Moon and Jupiter
Jupiter and the waxing crescent Moon form a nice grouping on July 9, 2016 with an occultation visible from the southern tip of Africa

Moon, Mars, Saturn and Antares
The Moon, Mars and Saturn close together during evenings from July 14 to 16, 2016

Meteor Shower
Delta Aquariids (Aquarids) meteor showers peak on July 29, 2016

R Aquilae within binocular range
Mira type variable star R Aquilae (R Aql) now within binocular range

The Planets
This Month's Guide

Algol Minima
Algol eclipse dates and times for July 2016

Comet
PanSTARRS (C/2013 X1) a binocular and small telescope comet.

Northern Hemisphere
Evening
West:- Jupiter (mag. -1.8)
South:- Mars (mag. -1.4 to -0.8), Saturn (mag. +0.2)
Midnight
Southwest:- Mars, Saturn
Southeast:- Neptune (mag. +7.8)
East:- Uranus (mag. +5.8)
Morning
South:- Neptune
Southeast:- Uranus

Southern Hemisphere
Evening
West:- Venus (mag. -3.9), Mercury (mag. -1.2 to -0.2) both second half of the month
West:- Jupiter
Northeast:- Mars, Saturn
Midnight
West:- Mars, Saturn
Northeast:- Neptune
East:- Uranus
Morning
Northwest:- Neptune
North:- Uranus

Deep Sky
Naked Eye:-
Melotte 111 - Mel 111 - The Coma Star Cluster (Open Cluster)
Messier 44 - M44 - The Praesepe (Open Cluster)
NGC 869 and NGC 884 - The Double Cluster - Open Clusters
Binoculars / Small telescopes:-
Messier 13 – M13 - Great Hercules Globular Cluster
Messier 3 - M3 - Globular Cluster
Messier 81 - M81 - Bode's Galaxy (Spiral Galaxy)
Messier 82 - M82 - Cigar Galaxy (Starburst Galaxy)
Messier 27 - M27 - The Dumbbell Nebula (Planetary Nebula)

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