Messier 14: Globular Cluster in Ophiuchus

Messier 14 is the quiet member of the Ophiuchus globular clusters. It sits in a bare stretch of sky away from the better-known M10 and M12, and it is harder to resolve than either.

What it is

M14 is a globular cluster, a dense ball of old stars bound by gravity in the halo of the Milky Way. It is almost twice as far away as M10 and M12, at about 29,800 light-years, and its 11′ apparent size works out to roughly 95 light-years across, so it is similar in true size to them. Its stars are spread fairly evenly, without a sharp bright core. M14 is rich in variable stars, which astronomers use to study the cluster's age and distance. It is also one of the few globular clusters in which a nova has been recorded: a star in the cluster flared up in 1938.

When to see it

M14 is a summer object. From about 40°N it is highest in the south around 11 p.m. daylight time in early July, and it is well placed in the evening through August. It climbs to about 47° above the horizon at 40°N. It lies just south of the celestial equator, so it is equally visible from the Southern Hemisphere.

How to find it

The area around M14 has no bright stars, so use Beta Ophiuchi (Cebalrai), a 2.8-magnitude star in the northeastern part of Ophiuchus, about 8° south-southeast of Rasalhague (Alpha Ophiuchi). M14 lies about 8° south of Beta Ophiuchi, slightly to the west. You can also reach it from M10: M14 is about 10° due east of M10, at almost the same declination.

What you will see

In binoculars M14 is a small, faint, round smudge, visible from a dark site but easy to miss from the suburbs. A 70–100 mm telescope shows an evenly lit, slightly oval glow with little central brightening and no resolved stars. A 200 mm or larger telescope at high power gives the glow a grainy texture, and the faintest stars at the edge begin to show, but the cluster never breaks up the way M12 does. No filter helps.

History

Charles Messier discovered M14 in early June 1764 and described it as a round nebula without stars. William Herschel was the first to resolve it into stars, in the 1780s. The 1938 nova was not noticed at the time; it was found only in 1964, when photographic plates taken in 1938 were examined. It was the first nova seen in a globular cluster since one in M80 in 1860.