The Caldwell Objects

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tor was obviously superior to Herschel's stoppeddown
speculum mirror. Had Messier used a 6inch
or smaller scope with a speculum mirror
during his sweeps of Sextans, the galaxy would
not have been an obvious sight. Walter Scott
Houston also had some trouble seeing the galaxy
in a small instrument: "Though I have observed
NGC 3115 with a 4-inch telescope from
Connecticut, averted vision was occasionally
needed to find it." ("Scotty" adds, however, that
the galaxy appeared "small but sharp" in a 5-inch
"apogee" scope.) I believe a combination of
factors were against Messier. When we go out to
find NGC 3115, we usually look when the object
is highest in the sky—that is, when it is near the
meridian. But Messier did not have that luxury.
He was a comet hunter sweeping the sky shortly
after sunset or shortly before sunrise. So his
sweeps through Sextans would have occurred
when the constellation was either dipping
toward the setting Sun or emerging from the
dawn. The combination of his marginal optics
and less-than-perfect observing circumstances
plausibly would have placed the galaxy out of
visual reach. Then again, perhaps Messier, like
many of us, simply shied away from the Sextans
void.
The origin of the galaxy's nickname, "The
Spindle," is somewhat of a mystery. In his 1978
Celestial Handbook, Robert Burnham Jr. writes that
NGC 3115 is "[p]opularly called the 'Spindle
Nebula,'" but he fails to credit a source for the
name. That Burnham uses the word "nebula"
instead of "galaxy" could imply that the word
"spindle" predated our knowledge of galaxies.
Then again, in the early and mid-1900s, the two
words were used interchangeably, even though
astronomers knew the difference. For instance,
M31, the Great Galaxy in Andromeda, was still
being called the Great Nebula in Andromeda
when I was young. Neither Smyth, the Rev. T.W
Webb, nor
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the Herschels describe NGC 3115 as a spindle.
In the 1962 Larousse Encyclopedia of Astronomy,
Lucien Rudaux and Gerard de Vaucouleurs make
no reference to the Spindle, but they do call NGC
3115 an "Elliptical Nebula." This led me to believe
that the name was probably applied to the object
between 1962 and 1978, when Burnham's
Handbook was published. So I checked the 1968
edition of Ernst Hartung's Astronomical Objects for
Southern Telescopes and found a possible solution.
Of NGC 3115 Hartung writes, "This elliptical
extra-galactic nebula looks like a bright pointed
spindle." Burnham occasionally references
Hartung's work, so it is possible that Burnham
picked up the word "spindle" from Hartung.
Yet the "spindle" appears so prominent in
photographs of NGC 3115 taken earlier this
century, I found it hard to believe that some
astronomer would not have referred to the
galaxy by that name. I mentioned this suspicion
to Brent Archinal, and he once again came to the
rescue by finding a paper by Frank G. Pease
entitled, "Photographs of nebulae with the 60inch
reflector 1911-1916," which was published
in a 1917 issue of the Astro-physical Journal Pease
described a 100-minute plate of NGC 3115 thus:
This is a bright spindle with an oblate center, which
measures about 30" x 35". The disk lies in p=45°, is
about 6" wide, and strong and continuous for about
45" either side of the nucleus; then come several
interruptions and knots. The whole lies within an
elliptical halo of nebulosity 3' x 1'.
So Pease and Hartung may be independent
sources for this popular nickname.
Hubble classified NGC 3115 as an E7
galaxy. He based his opinion on the way the
galaxy appeared on plates taken with the 60-
Deep-Sky Companions: The Caldwell Objects