M14 - Globular Cluster in Ophiuchus

Click on the image to see it 2x this size.


Discovered by Charles Messier in 1764.

Messier 14 (M14, NGC 6402) is a slightly elliptically shaped stellar swarm, about 100 light years across and about 30,000 light years away. While its bright main body about only about 3 arc minutes in angular diameter, the cluster's outlayers reach out to a total apparent diameter of 11.7 arc min. Its apparent visual brightness of 7.6 visual magnitudes corresponds to an absolute magnitude of -9.12, or to a luminosity about 400,000 times that of our sun - so while, because of its greater distance, it is apparently dimmer than the two other great Ophiuchus clusters, M10 and M12, it is intrinsically much more luminous.

M14 contains the considerably large number of over 70 variables, many of them W Virginis stars (Population II Cepheids; Demers and Wehlau 1971).

In 1938, a nova appeared in M14, which however was not discovered before 1964, when Amelia Wehlau of the University of Western Ontario surveyed a collection of photographic plates taken by Helen Sawyer Hogg between 1932 and 1963 (Hogg and Wehlau, 1964). This nova was visible on 8 plates, taken between June 21-28, 1938, as a 16th mag star - this faintness explains, at least in part, why it had not been discovered earlier. Mrs. Hogg has estimated that this corresponds to an absolute magnitude of -1.5 (a modern check yields -0.7), but thought that at its maximum, it should have been as bright as mag 9.2, or absolute magnitude -7.5 (modern check), or almost 5 magnitudes brighter than the brightest cluster members! This was the second known nova in a globular cluster after that of 1860 in M80, T Scorpii, and the first one ever photographed. In 1983, the 4-m telescope of CTIO and the 3.9-m Anglo-Australian Telescope were used in attempt to look for a remnant of the nova (Shara et.al. 1986). In 1991, astronomers used the Hubble Space Telescope to observe the field around this nova in M14, but could not find the star or a nebulous remnant (Margon et.al. 1991).

Globular cluster M14 is one of the original discoveries of Charles Messier who cataloged it on June 1, 1764 and described it as a round nebula without stars. It was first resolved into stars by William Herschel in 1783.

Globular cluster M14 was the first CCD image taken, according to TheSky advertising.

Click on the image above to see it twice as large.

Imaging Details: 

Scope: Planewave 12.5" CDK
Camera: Apogee U16M w Astrodon Gen II LRGB filters
Mount: Paramount ME (MKS5000)
Guiding: SBIG ST-402ME and Astrodon MMOAG
RGB: 6/5/5 x 10min
Luminance: 9x10min
Image acquisition via TSX and CCD-Commander
Calibration and combines in Maxim
Processed in PS CC 2015
Re-registration of the final product using RegiStar

Lucknow, Ontario, Canada
July, 2015