The Caldwell Objects

7
N G C 4 0 4
T y L p e n : G t a i l ( c a S x u O y l ) a r
C o A n d : r o m e d a
RA:01 h 09.4 m
Dec: +35° 43'
Mag: 10.3
SB: 14.0
Diam: 6.6'
Dist: 8 million light-years
NGC 404 is truly a hidden treasure. This lentic-
ular galaxy lies only 6' northwest of the 2nd-
magnitude topaz star Beta (β) Andromedae
(Mirach), whose light interferes with — but does
not drown out — this bright little gem. NGC 404
belongs to a small group of galaxies in the Coma-
Sculptor Cloud and is approaching us at a speed
of 35 km per second. The galaxy is quite small,
measuring only 16,000 light-years in diameter,
and images of it through large telescopes reveal it
to be a roundish spiral. Its small bulge contrasts
well with a surrounding dust ring. The galaxy is
just visible in a 60-mm refractor, and it takes
magnification remarkably well, so use enough
power to remove Beta Andromedae from your
field of view. In the 4-inch the circular galaxy has
a milky-smooth texture. A faint "star" punctuates
its core; high-resolution images show that NGC
404 has a very small, extremely bright nucleus,
with a dark crescent and patchy whorls of
darkness in its lens. A 1995 Hubble Space
Telescope image of this region reveals a bright,
unresolved point source (less than 1 parsec
across) surrounded by several fainter ones. The
latter are presumably star-forming regions
responsible for the galaxy's extended nebular
emission and for the young stellar features seen
in spectra of the nucleus.
8
Hockey Stick; The Hook
N G C 4 6 5 6
T y B p a e r S : r p G e i a d r l ( a S x p l B y e m c )
C o C n a : V n e n s a t i c i
RA: 12 h 44.0 m
Dec: +32° 10'
Mag: 10.5
SB: 14.8
Dim: 18.8' x 3.2'
Dist: 23.5 million light-years
Larry Mitchell of the Houston Astronomical
Society first introduced me to NGC 4656 during
the 1998 Texas Star Party. He calls it the Hockey
Stick galaxy, while his observing compatriot
Barbara Wilson refers to it as The Hook. After
seeing this galaxy through their large reflectors, I
understand both monikers. Situated ½° southeast
of NGC 4631 (Caldwell 32), NGC 4656 is an
irregular barred spiral galaxy, merely 10° from
edge on, with a warped appendage on its
northeastern end. Known as NGC 4657, this
appendage juts out at right angles to the main
shaft like the hooked blade of a hockey stick. The
most likely explanation for NGC 4656's distorted
appearance is a tidal interaction between it and
NGC 4631. In his 1994 Carnegie Atlas of Galaxies,
Allan R. Sandage writes that the pair's atomichydrogen
gas has provided evidence of a tidal
encounter between the two galaxies. The two are
350,000 light-years apart on the plane of the sky.
Wilson likens these interacting spirals to "two
ships nearly crashing in the night, both listing
from the encounter, with [NGC] 4656 definitely
the loser, but [NGC] 4631 . . . not unscathed."
NGC 4656 is easily visible in the 4-inch
Genesis. Southwest of what may be considered
its nuclear region, the galaxy is bright; on the
Twenty Spectacular Non-Caldwell Objects 435