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Messier 15: Pegasus’ huge stellar metropolis

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Globular cluster Messier 15 is each an excellent telescopic sight and an excellent imaging goal. Picture: Adam Block.

Messier 15 (NGC 7078) in Pegasus is a showpiece object of the early autumn sky and one of many best globular clusters to grace the northern sky. Globular clusters are a very spectacular class of deep-sky object, being densely-packed and near-spherical collections of historic stars.

Beneath a pristine darkish sky, eagle-eyed observers might spot it with the bare eye; by means of 10 x 50 binoculars it seems as a vibrant, fuzzy ball. Messier 15 lies properly above the celestial equator, so observers at mid-northern latitude received’t face any low-altitude points. Certainly, its observable all through September at an honest altitude from dusk by means of to close daybreak.

Messier 15 (NGC 7078) lies in western Pegasus, 4 arcminutes north-west of magnitude +2.4 Enif (epsilon [ε] Pegasi).

Learn how to observe:

Messier 15 shines at magnitude +6.0 and spans 16’ to 18’ at its fullest extent (sources differ on M15’s obvious diameter). It’s positioned 4 arcminutes north-west of magnitude +2.4 Enif (epsilon [ε] Pegasi), a place that from London sees it culminate shortly after 10.30pm BST at an altitude of round 50 levels.

A telescope within the 80mm (~three-inch) class exhibits Messier 15 as a vibrant unresolved haze some 4’ in obvious diameter. It’s a well-concentrated globular that’s rated IV on the I to XII focus scale. A 150mm (six-inch) telescope, working an influence of round 200x, intensifies the core’s look, although you’ll want the resolving energy of at the least a 200mm (eight-inch) ’scope to start to select the cluster’s outlying stars. On a gentle and clear evening, a 300mm (12-inch) telescope can resolve Messier 15 to its core.

Can you notice planetary Pease 1?

Messier 15 is one in all a small, choose group of globular clusters that may boast the presence of a planetary nebula amongst their teeming stars. Pease 1 was the primary planetary to be detected inside a globular cluster when, in 1927, American astronomer Francis Gladheim Pease noticed the nebula on a photographic plate taken with the 100-inch (~2.5-metre) Hooker Telescope at Mount Wilson Observatory in California, USA. 

That object, at the moment generally known as Pease 1 and catalogued moreover as PK 65-27.1, shines faintly at magnitude +14.9 and lies simply 1.5’ north-east of Messier 15’s core. It exhibits up properly in the perfect novice photographs however is a tricky visible problem, owing partly to its diminutive 3” obvious diameter and its place near Messier 15’s core, the place it’s embedded deeply amongst many stars of comparable brightness.

To have any likelihood of discovering it, a magnification of round 300x will must be dropped at bear on a really clear and nonetheless evening. If stars are twinkling fiercely overhead, overlook it! A 250–300mm (ten- to twelve-inch) telescope could also be adequate to trace it down; when you’re certain that you just’re trying in the fitting place, slip an O-III filter into the sunshine prepare.

Pease 1 is a tiny planetary nebula embedded in Messier 15. Picture: Hubble/NASA.
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