The Caldwell Objects

the center. A faint outer halo is also suggested. At
72x the galaxy's core looks tight, though not
stellar. The Γ-wide core also seems elongated and
mottled. Christian Luginbuhl and Brian Skiff
found that through a 6-inch telescope the eastern
edge of the galaxy's halo has a "granular" texture
and with a 10-inch the galaxy "looks like an
unresolved globular cluster."
NGC 147, however, is a demon at 23x. The
region contains several clumps of field stars that
mimic hazes, and only after careful plotting did I
recognize NGC 147's true glow. (Do rely on both
the chart and the photograph provided here to
pinpoint it.) Dark skies are an absolute must for
this dim galaxy. NGC 147 clearly looks more oval
than NGC 185. Long and careful study of NGC
147 at 23x revealed hints of an elliptical center
surrounded by a large, albeit faint, lens of light.
Many times my eye caught the lens-shaped core
of this ellipti-
The Caldwell Objects
17 & 18
cal system quite clearly; at other times, a larger,
extended halo appears to round it out. The outer
halo is contained within a sharp diamondshaped
pattern of bright field stars. At 72x the
galaxy seems to scintillate with minute sparkles
of light. Perhaps this is an illusion created by
stars superposed on the galaxy. The more nights
I spent observing this galaxy, the easier it
became to pick out its faint glow on successive
nights. This underscores how experience can
make us better — and more efficient —
observers.
M31 and its four brightest companions
(NGC 147, NGC 185, M32, and Ml 10) are all
members of the larger Coma-Sculptor Cloud of
galaxies. In a 1998 Astronomical Journal article
Sidney van den Bergh (Dominion Astro-physical
Observatory, Canada) stated that NGC 147 and
NGC 185 probably form a stable binary system,
orbiting M31 together like affectionate siblings.
NGC 147's linear diameter is 12,000 light-years,
while NGC 185 measures 11,000 light-years
across; you could fit fully 10 galaxies the size of
either dwarf across the length of the Great
Andromeda spiral. In 1995 astronomer Paul
Hodge (University of Washington) announced
spectral evidence for some ongoing star
formation in NGC 185. But in 1999 a trio led by
David Martinez-Delgado (Astrophysical Institute
of the Canaries, Spain) found that most of NGC
185's stars were formed at an early stage in the
galaxy's evolution. "After that," these researchers
write, "star formation proceeded at a low rate
until the recent past, the age of the most recent
traces of star formation activity detected in the
galaxy being some 100 million years." They
found no evidence for stars younger than a
billion years beyond the galaxy's innermost few
hundred light-years. "Since the larger
concentration of stars of any age lies in the
central part of a galaxy," Martinez-Delgado and
his colleagues con-
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