The Caldwell Objects

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NGC 4565
Type: Spiral Galaxy (Sb)
Con: Coma Berenices
RA: 12 h 36.3 m
Dec: +25° 59'
Mag: 9.6
Dim: 16.2' x 2.3'
SB: 12.9
Dist: 32 million light-years
Disc: William Herschel,
1785
W. H ERSCHEL: [Observed 6
April 1785] A lucid ray 20' long
or more. 3' or 4' broad from north preceding to south
following [from northwest to southeast]. Very bright in
the middle. A beautiful appearance. (H V-24)
M ORE THAN ANY OTHER DEEP- SKY OBJECT,
the sight of the edge-on spiral galaxy NGC 4565
jars my imagination, causing me to wonder about
the unseen vistas hiding beyond its dusty
confines. Compare the photograph of NGC 4565
above with that of the nearly face-on system IC
342 (Caldwell 5) on page 30. To me NGC 4565
looks more mysterious than IC 342. But why?
Perhaps it's because order can be seen in longexposure
photographs of face-on spiral galaxies:
multitudes of stars cling like nettles to wellstructured
arms; dust accumulates rather neatly
in channeled lanes. Seen from above, a spiral
galaxy is a recognizable visual vortex, a snapshot
of celestial water pouring down a drain. Similar
spiral structure abounds on Earth — in the
unfolding of a flower, in swirling autumn leaves,
or in the spinning arms of a hurricane.
Edge-on systems, in contrast, lack that
immediacy of recognition. Most of their treasures
are hidden behind turgid veils of dust.
150
G C / Ν G C: Bright, extremely large, extremely extended
toward position angle 135°, very suddenly brighter in the
middle to a nucleus equaling a star of magnitude 10 or 11.
From our limited perspective it appears that we
see more darkness than light, lending these
galaxies a supernatural quality that attracts our
curiosity. One might think that 19th-century
astronomers would have seen these curious
"nebulae" as their contemporaries saw the jungles
of Africa from passing ships — "so hopeless and
so dark," in the words of Joseph Conrad's
Marlow, "so impenetrable to human thought."
But in 1855 William Parsons, the third Earl of
Rosse, described NGC 4565 as a "beautiful object"
after seeing it through his 72-inch reflector. Using
that powerful telescope five years earlier, Lord
Rosse had drawn the equatorial dust lane in
another edge-on system, NGC 891 (Caldwell 23).
At that time he also discovered the spiral nature
of some "nebulae" and likened them to nascent
planetary systems. The clairvoyant John
Herschel, however, had already hinted that
extended nebulae were perhaps round nebulae
seen edge on. NGC 891, in particular, gave him
the impres-
Deep-Sky Companions: The Caldwell Objects