The Caldwell Objects

The galaxy received some incidental recognition
after January 1996, when the public first saw the
now-famous Hubble Deep Field — a 10-day-long
Hubble Space Telescope exposure revealing at
least 1,500 new galaxies, some as faint as 30th
magnitude, in an area of sky only 2 across. ' The
Deep Field lies only about 42' to the northwest of
NGC 4605, which often appeared in photographs
and finder charts that were published to help
amateurs locate the tiny sky patch scrutinized by
Hubble. Through the Genesis NGC 4605 (whose
true linear diameter is a modest 22,000 lightyears)
appears as a warped bar, oriented
northwest to southeast, surrounded by a spindle
of light. Its disk displays a mottled texture and
has a large and obvious patch of dust in its
northwestern quadrant. Long-exposure
photographs reveal a larger envelope
surrounding the spindle, several ΗII regions,
and what appears to be a tiny galaxy protruding
from NGC 4605's southeastern tip. NGC 4605
resides in the Coma-Sculptor Cloud of galaxies
and is receding from us at 140 km per second.
2
N G C 7 7 8 9
T y O p e C : n l u s t e r
C o C n a : s s i o p e i a
RA: 23 h 57.0 m
Dec: +56° 43'
Mag: 6.7
Diam: 25'
Dist: 6,000 light-years
Just 3° southwest of Beta (β) Cassiopeiae, or
Caph (the westernmost star in Cassiopeia's
famous W asterism), and midway between Rho
(ρ) and Sigma (σ) Cassiopeiae, lies the large,
uniform glow of NGC 7789. This star cluster is a
magnificent spectacle in 7x35 binocu-
lars, appearing nearly as large as the full Moon
and just as round. In fact, when seen through
binoculars the cluster looks like a tailless comet
crossing the rich star fields of the northern Milky
Way. NGC 7789 lies at or just beyond the limit of
unaided vision, making it a great naked-eye
challenge under dark skies. The Rev. T W Webb, .
in his Celestial Objects for Common Telescopes, calls
it a" [b]eautiful large faint cloud of minute stars,"
while John Herschel called it a "most superb"
cluster. Piazzi Smyth, though, saw NGC 7789 as a
"mere condensed patch in a vast region of
inexpressible splendour, spreading over many
fields; including the whole Galaxy through this
and the adjacent constellations." At its estimated
distance of 6,000 light-years, the cluster's angular
diameter corresponds to a respectable physical
size of 44 light-years. There are 583 stars in the
cluster, with the brightest shining at magnitude
10.0. Many of NGC 7789' stars can s be spied at
23x, and higher magnification shows a distinct
background of unresolved suns. Equally
impressive in wide-field telescopes is the
complex of dark nebulae in and around the
cluster. These impressive veils are not outlined
on any star atlas that I'm aware of.
3
N G C 2 81 a n I 1 d C 5 9 0
T y E p m e i : Ne s b s a u i n l O o d p a n C e l n u s t e r
C o C n a : s s i o p e i a
RA: 00 h 52.8 m
Dec: +56° 38'
Mag: 8.0 (nebula); 7.4 (cluster)
Dim: 35' x 30' (nebula)
Diam: 4.0' (cluster)
Dist: ~7,500 light-years
The third object in this short list, NGC 281 in
Cassiopeia, is a bit of an enigma. Sky Atlas
Twenty Spectacular Non-Caldwell Objects 431