This relatively bright object in the deep sky is now in a good place to view.
The globular cluster M15 is about 36,000 light-years away, but shines so well that it becomes a must-see object through your telescope.
Credit: Don Goldman
- M15 is a magnitude 6.2 globular cluster within the Pegasus constellation, measuring 12.3′ in diameter and visible to the naked eye from dark observation sites.
- Located by extending a line of 4° from Theta through Epsilon Pegasi, M15 displays resolved stars and star chains through a 4-inch telescope, giving an elliptical morphology.
- Advanced observations with an 11-inch or larger telescope enable the detection of Pease 1, the inaugural planetary nebula identified within a globular cluster, located about 1′ northeast of M15’s core.
- Successful observation of Pz 1 requires a magnification of 200x or greater, application of a nebula filter, and favorable atmospheric viewing conditions to distinguish the object from the surrounding stellar population.
If you live in the Northern Hemisphere and are looking for a great object to see on an autumn night, M15 is a showpiece globular cluster that resides within the boundaries of the Pegasus constellation, the winged horse. It is quite large, measuring 12.3′ in diameter.
From a dark observing site, sharp-eyed observers can see this magnitude 6.2 cluster with their naked eyes. Not to be confused by the magnitude 6.1 star just 17′ to the east. Confirm your vision through binoculars or a telescope.
And speaking of telescopes, a 4-inch scope will see dozens of stars surrounding M15’s extremely bright core. Notice the chains of stars emanating from its central region. Through a small telescope, these star patterns lead some observers to describe M15 as slightly oval.
The M15 is very easy to find. Use Theta and Epsilon Pegasi as indicators. Simply draw a line from theta to epsilon, and continue another 4°. By the way, 4° is the width of two fingers held at arm’s length.
look deeply
With an 11-inch or larger telescope, try for the challenge object inside M15 – Pz1, the first planetary nebula found within the globular cluster. In 1928, American astronomer Francis Gladheim Pease discovered the object when he observed an unusually bright ”star” on a photographic plate taken with the 100-inch Hooker telescope on Mount Wilson.
View this planetary nebula through an eyepiece that will give you a magnification of 200x or more. Use Nebula Filter. The filter will suppress the brightness of the numerous stars around Pz1. Be aware of sky conditions. You’ll need good eyesight to see the minor planet, which lies about 1′ northeast of M15’s core. If your vision is poor, try it on another night. But, hey, even looking average, the M15 will delight you.
