Credits: NASA, ESA, STScI and F. Ferraro (Universita di Bologna)
Discovered by Charles Messier in 1764, the globular cluster M14 is home to over 150,000 stars and has an apparent magnitude of 8.3.
It is located 29,000 light-years away from Earth in the constellation Ophiuchus, and is best observed with a telescope during July.
In the summer of 1938, M14 played host to a nova — an extraordinarily rare event in a cluster of its kind. A nova is a sudden stellar eruption where, in just a few days, a star’s brightness increases by a factor of 10,000. Then over the following months the outburst fades away and the star returns to its normal brightness.
This image of M14 was assembled using both infrared and visible-light observations from Hubble. Its stair-step appearance results from the design of the camera used to take the exposures. The camera consisted of four light detectors, one of which provided a higher resolution but had a smaller field of view than the other three. Because the detector with the higher resolution did not cover as much area as the others, black regions are left around its image segment when the exposures from all four detectors are combined into one picture.
Facts about M14 by Keith Turnecliff
Messier 14 (also known as M14 or NGC 6402) is a globular cluster of stars in the constellation Ophiuchus. It was discovered by Charles Messier in 1764.
At a distance of about 30,000 light-years, M14 contains several hundred thousand stars. At an apparent magnitude of +7.6 it can be easily observed with binoculars. Medium-sized telescopes will show some hint of the individual stars of which the brightest is of magnitude +14.
The total luminosity of M14 is in the order of 400,000 times that of the Sun corresponding to an absolute magnitude of -9.12. The shape of the cluster is decidedly elongated. M14 is about 100 light-years across.
A total of 70 variable stars are known in M14, many of the W Virginis variety common in globular clusters. In 1938, a nova appeared, although this was not discovered until photographic plates from that time were studied in 1964. It is estimated that the nova reached a maximum brightness of magnitude +9.2, over five times brighter than the brightest 'normal' star in the cluster.
Slightly over 3° southwest of M14 lies the faint globular cluster NGC 6366.