The Caldwell Objects

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NGC 147
Type: Elliptical Galaxy (E5
pec)
Con: Cassiopeia
RA: 00 h 33.2 m
Dec: +48° 30'
Mag: 9.5
Dim: 17.8' x 11.0'
SB: 14.7
Dist: 2.3 million light-years
Disc: John Herschel, 1829
J. H ERSCHEL: [Observed 8
September 1829] Very
faint, very large, irregularly round, 4' to 5' diameter,
loses itself insensibly, has a magnitude 11 star in cen-
tre. (h29)
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NGC 185
Type: Elliptical Galaxy (Ε3 pec)
Con: Cassiopeia
RA: 00 h 39.0 m
Dec: +48° 20'
Mag: 9.2
Dim: 17.0' x 14.3'
SB: 14.7
Dist: 2.3 million light-years
ALTHOUGH THE DWARF ELLIPTICAL GALAXIES
NGC 147 and NGC 185 lie within the boundaries
of Cassiopeia, they are in fact companions of, and
gravitationally bound to, the great Andromeda
spiral galaxy M31, which looms some 7° to the
south. (Here is a classic example of the arbitrary
nature of constellation boundaries.) Both dwarf
galaxies are essentially at the same distance as
M31. NGC 147 is
GC/NGC: Very faint, very large, irregularly round, gradually
then suddenly much brighter in the middle to a star of
magnitude 11.
Disc: William Herschel, 1787
17 & 18
W. H ERSCHEL: [Observed30 November 1787] Pretty bright, very
large, irregularly round, very gradually much brighter in the
middle, resolvable, 5' or 6' diameter. (Η II-707)
GC/NGC: Pretty bright, very large, irregularly round, very
gradually much brighter in the middle, resolvable.
approaching us at a speed of 163 km per second
and NGC 185 is doing so at 211 km per second.
By comparison, M31 is rushing toward our solar
system at 298 km per second. These velocities
suggest that the two dwarfs are in a similar phase
in their orbit about M31, either approaching the
grand spiral from our side or heading away from
it on the spiral's far side. Most astronomers
would take the dwarfs'
The Caldwell Objects 75