The Caldwell Objects

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us, its central lens, and its spiral arms, which look
as thin and frail as old sewing thread. Tiny knots,
like filigree, adorn the arms, which become
frayed at the ends. Of NGC 2775's photographic
appearance Edwin Hubble wrote in 1961: "Notice
that the arms cannot be traced as individual
structures but rather as separate segments . . . The
arms, with their associated dust lanes, start
abruptly at the edge of a completely amorphous
central nucleus and lens. The boundary between
the lens and the spiral structure is sharp." We see
the galaxy inclined 39° from face on, so the arms
appear to wrap around the central lens in an
oblique, ringlike fashion. Despite its tender
appearance, the galaxy is quite large. Accepting
an estimated distance of 55 million light-years,
the galaxy measures 73,000 light-years across and
has a total luminosity of 17 billion Suns. It is
receding from us at a speed of 1,135 km per
second. The galaxy's spectrum is dominated by
the light of old, cool stars.
NGC 2775 belongs to the Antlia-Hydra
Cloud of galaxies, which has 106 members with
known redshifts. It is also the largest member of
the sparse NGC 2775 group, a few of whose
members can be seen peppering the photograph
on page 191. Just 11' northeast of NGC 2775 is
NGC 2777, an amorphous 14th-magnitude galaxy
that is plotted on the Millennium Star Atlas. A
1981 Arecibo radio-telescope map of the group
shows a cloud of neutral atomic hydrogen (Η I)
gas extending from NGC 2777 toward NGC 2775.
There is no evidence for an interaction in visiblelight
photographs. Are the two galaxies tidally
interacting? No, but a recent Very Large Array
radio map of the complex reveals a neutralhydrogen
bridge between NGC 2777 and "U3," an
anonymous companion galaxy that is about 3.5'
west-southwest from NGC 2777 and about 3
magnitudes fainter than NGC 2777. In a 1996
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American Astronomical Society abstract, David
E. Hogg and Morton S. Roberts (National Radio
Astronomy Observatory) argue that radio maps
of this neutral-hydrogen bridge clearly indicate
that U3 and NGC 2777 are interacting.
At 23x in the 4-inch NGC 2775 displays a
starlike core surrounded by a slightly oval haze
that's oriented northwest to southeast.
Many dim double stars populate the field, and
some are tight enough to look fuzzy at low
power — creating the illusion that the group's
dim and distant galaxies can be seen in the 4inch.
At higher powers NGC 2775 remains
largely elusive. The northeastern side may be
brighter than the southwestern side, and hints of
mottled clumps pop in and out of view in the
galaxy's halo. All this detail is at the limit of
vision with the 4-inch. But do concentrate on the
galaxy's feeble light, because the southeastern
extremity seems to have a faint arc suggesting
spiral structure, though nothing remains visible
long enough for me to be certain. See if the
northern and western sectors don't also show
some type of visual enhancements. Observers
with telescopes as large as 20 inches have failed
to see more structure.
On September 23, 1993, the Leuschner
Observatory Supernova Search — which used an
automated 30-inch telescope equipped
Deep-Sky Companions: The Caldwell Objects