The Caldwell Objects

8
Ghost’s Goblet
NGC 559
Type: Open Cluster
Con: Cassiopeia
RA:01 h 29.5 m
Dec: +63° 18'
Mag: 9.5
Diam: 7.0'
Dist: 3,700 light-years
Disc: William Herschel, 1787
W. HERSCHEL: [Observed 9
November 1787] A com-
pressed cluster of some pretty
[bright] and many very [faint]
stars. Irregularly round. 6' or
7' diameter. (H VII-48)
GC: Cluster, bright, pretty large, pretty rich, stars of NGC: Cluster, bright, pretty large, pretty rich,
mixed magnitudes.
F OR STARWATCHERS IN THE N ORTHERN
Hemisphere, late autumn signals a time of
change. Hot and hazy nights are replaced with
brisk and transparent evenings. The powerful
glow of the summer Milky Way, with its awesome
central bulge, has all but slipped into the
twilight. High in the north, a more delicate river
of stars arches over the celestial pole. In its midst
five bright stars trace a wide Μ (or W) that
dominates the view, looking somewhat like a
newborn deer extending its legs in an attempt to
stand for the first time. These stars, which belong
to the constellation Cassiopeia, lie in the direction
of the Milky Way's outer fringes (though
nowhere near as far).
The density of stars we see surrounding
Cassiopeia increases sharply around the famous
Μ asterism because that asterism lies on the
galactic equator — the dense midplane of the
8
galactic disk. It is a region rich in galactic, or
open, star clusters. If you draw a 4°-wide circle
around the midpoint between the 3rd-magnitude
stars Delta (δ) and Epsilon (ε) Cassiopeiae, you
will find at least eight such clusters within the
reach of binoculars or a small telescope. The
westernmost of these clusters is NGC 559
(Caldwell 8).
Most open clusters, which are loose packs of
physically associated stars, will usually reward
viewers no matter what size instrument is used
to see them. But their visual beauty can be subtle.
Take NGC 559, for example. The cluster shines
meekly at magnitude 9.5. About 120 stars
populate the cluster, but only about 40 of them
are of magnitude 12 or brighter; the brightest
cluster member is a paltry magnitude 9.0. The
cluster's surface brightness (13.7 magnitudes per
square arcminute) further
The Caldwell Objects 41