|Right Ascension||05 : 24.2 (h:m)
|Declination||-24 : 31 (deg:m)
|Visual Brightness||7.7 (mag)
|Apparent Dimension||9.6 (arc min)
Discovered 1780 by Pierre Méchain.
Globular cluster Messier 79 (M79, NGC 1904) is a nice globular cluster in an unusual place for this kind of objects, in the hemisphere opposite to the Galactic Center, in the inconspicuous constellation Lepus.
M79 was found by Pierre Méchain on October 26, 1780, and reported his discovery to his friend and colleague, Charles Messier, who determined its position and included it in his catalog on December 17, 1780. It was first resolved into stars and recognized as a globular cluster by William Herschel in about 1784.
M79 is a beautiful globular cluster at a quite unusual location in the sky: Most globulars are grouped around the Galactic center, but this is one of the few which are situated in the other hemisphere, i.e. it is beyond us for hypothetical observers in the central stellar bulge of our Milky Way galaxy. It is little over 40,000 light years from us, but about 60,000 light years from the galactic center.
At this distance, M79's apparent diameter of 9.6 minutes of arc corresponds to a linear extension of about 118 light years. This cluster is slightly elliptical, extended at position angle 45 deg. It is receding from us at about 200 km/sec. As of July 2013, this cluster contains only 12 or 13 known variables, according to Clement (2013): 10 RR Lyrae stars (6 of type RR0, 4 of RR1), 1 semi-regular variable, and 1 long-term variable (the star M79-V7), perhaps a long-period type II Cepheid (type CW); 1 star (M79-V8) is of uncertain type and to be confirmed. Current state of variable star research in M79 is presented in Kains et.al. (2012).
Globular cluster M79 has a considerably dense core, which is thought to have possibly undergone a core collapse process, as have the globulars M15, M30, M70, and possibly also M62.
The position of M79 is given erroneously in many older references, including the Sky Catalogue 2000.0 and the NGC 2000.0: at RA 05:24.5 Dec -24:33 instead of the correct values, RA 05:24.2 Dec -24:31 (J2000.0), a notion of the present author. The source of the error is currently researched.
In 2003, it was found that M79 is perhaps a rather new immigrant into the globular cluster system of our Milky Way: It may come from, or still be a member, of the remnant globular cluster system of the Canis Major Dwarf galaxy, a dwarf spheroidal galaxy which is currently undergoing a very close encounter with our Galaxy, and in progressive state of dissolution. Together with M79, three more globular clusters are suspected to have immigrated from the Canis Major Dwarf: NGC 1851, NGC 2298, and NGC 2808.
About 0.5 degrees to the SW of M79 lies the 5.5 mag star ADS 3954 with its 7th mag companion, separated by 3".
Last Modification: May 23, 2014