The Caldwell Objects

lowing night fell clear, when Herschel returned to
his "potential planet" he discovered that" [t] he
small star is still 1.5 diam. from edge. It has
therefore not moved perceptibly, and is therefore
not a planet." We do not need to be at Herschel's
side to sense his disappointment. It's the feeling
every observer gets after he or she encounters a
strange nebulous glow and believes it might be a
comet — until its true identity as a star cluster or
faraway galaxy is revealed on a star chart.
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Today we know Herschel's planetary nebula as
NGC 2867, and we know that it is an expanding
shell of gas blown off the surface of a dim and
dying star. NGC 2867 is one of the easiest objects
of its type to spy in the sky. Shining at magnitude
9.7, it is only 0.9 magnitude (roughly a factor of 2)
fainter than M57, the famous Ring Nebula in
Lyra. But NGC 2867 is seven times smaller than
the Ring, so its light is much more concentrated
on the plane of the sky. In fact, the nebula has
such a high surface brightness that it appears
virtually stellar at low powers, a 10th-magnitude
"star" among the multitudes in the rich Carina
Milky Way. The object's field is a cinch to locate,
for it lies a little more than 1° northeast of the
2nd-mag-nitude star Iota (ι) Carinae (Aspidiske),
which marks the southeastern arm of the False
Cross. The nebula is the center "star" in a 10'-long
chain of three roughly 9th-magnitude, equallyspaced
suns oriented northwest to southeast.
Almost any instrument will show NGC
The Caldwell Objects 355