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Home | History | Science | Observations | LG Members
Observations of the Local Group of Galaxies
NGC 147
NGC 147 was discovered sometime during the 1820's by Sir John Herschel. It appeared in Herschel's catalogue of 1833 as object h22. Herschel's general catalogue of 1864 listed the galaxy as GC27. Dreyer descrided the galaxy as "very faint very large, irregularly round, gradually suddenly much brighter middle, star of 11th magnitude nearby".
Walter Baade in 1944 published "NGC147 and NGC185, Two new members of the local group of galaxies." in APJ 100 p147-150. He proposed that NGC 147 and NGC 185 were members of the local group because:
(1) With both are associated a few globular clusters which have angular diameters comparable to those of the globular clusters in the Andromeda Nebula.
(2) According to N.U.Mayall, the radial velocity on NGC 185 is -270km/sec, which after allowance for galatic rotation, corresponds to a peculiar radial velocity of -50km/sec. Both factsd indicate that NGC 147 and NGC 185 are nearby systems, comparable in distance to the Andromeda group.
He estimated that the absolute magnitude of the galaxy was -10.3, and after inspecting the photographic plates of the galaxy Baade detected 2 globular clustersin the galaxy. It it interesting to note that at the time of publication the number of local group galaxies was 13.
NGC 147 is a dwarf eliptical galaxy 2.8 million light years distant. The galaxy has an absolute magnitude of -14.6. At that distance the apparent magnitude of NGC 147 is 9.5. Like all dwarf eliptical galaxies there is no nucleus to the galaxy. This seems to follow the rule that elliptical's with an absolute magnitude less than -15.5 have no nucleus.
The brightest stars in NGC 147 have an apparent magnitude of about 18 and are mainly redgiants. No significant change in the stellar population is noticed across the galaxy. There is little neutral hydrogen in the galaxy - a complete contrast to its neighbour NGC 185. Four globular clusters are associated with NGC 147. These clusters are almost two magnitudes fainter than the clusters associated with the galaxy NGC 205 and four magnitude fainter than those clusters in M31. The brightest of these globulars have a magnitude of 16.9.
Andrew Murrell observing from Australia using a 20" ƒ/5.
NGC 147 is located 7 degrees north of M31 in the constellation of Cassiopeia. The galaxy lies close to the Milky way so the skybackground is bright with 7th and 8th magnitude stars. Through the eyepeice of a 10" scope the galaxy appears as an ellongated haze 8' by 4', oriented almost NE-SW. It has an even surface brightness with a slight brightening toward the middle of the galaxy. NGC 147 is well defined from the sky background and has several stars superimposed over its face. I have made no attempt to observe the globular clusters at this time.
Steve Dillinger observing from Colorado USA using a 10"
The galaxy is a large faint oval glow. Uniform in brightness. No nuclear condensation.
