The Caldwell Objects

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14 14 Double Cluster NGC 869 and NGC 884 Type: Pair of Open Clusters Con: Perseus NGC 869 RA: 02 H 19.0 M Dec: +57° 08' Mag: 5.3; 4.5 (O'Meara) Diam: 18' Dist: 7,300 light-years Disc. known since antiquity W. HERSCHEL: [Observed 1 November 1788] A very beautiful and brilliant cluster of [bright] stars, very rich. The middle contains a vacancy. (H VT-33) GC/NGC: Remarkable cluster, very large, very rich, stars ranging from magnitude 7 to 14. THERE'S A PARTY GOING ON IN THE SKY EVERY Christmas Eve, and it focuses on the Double Cluster in Perseus. This cheerful gathering of an imaginary celestial family is one you won't 62 NGC 884 RA: 02 H 22.0 M Dec: +57° 08' Mag: 6.1; 5.7 (O'Meara) Diam: 18' Dist: 7,300 light-years Disc. known since antiquity W. HERSCHEL: [Observed 1 November 1788] A very beautiful, brilliant cluster of [bright] stars, irregularly round. Very rich. Near ½° in diameter. (H VI-34) GC/NGC: Remarkable cluster, very large, very rich, ruby star in the middle. find mentioned in any previous book on star lore; it's a celestial play I created at the age of 10. (It sounds silly now, but it might make a good under-the-stars skit for children.) The Deep-Sky Companions: The Caldwell Objects
play begins at 8:00 p.m., when my eyes knock on the door of the northwestern horizon. If the night is clear, the door opens. And there, standing with perfect posture, is the matronly form of the Northern Cross. Dressed in the evening gown of the Milky Way, she welcomes me with open arms: "Why, Stephen, what a pleasant surprise! Come and join us!" Orion and his dogs suddenly burst through the back door of the southeastern horizon; winds lap at me like wet tongues, sending shivers up and down my spine. I look to the north and see three more friends, Cepheus, Cassiopeia, and Perseus, parading over the snowcapped hill of the celestial pole. My attention is drawn to Perseus because he carries a special gift wrapped in mist. The moment has come. I use my telescope, and the magic of magnification, to open the gift. The mist evaporates to reveal two crystal spheres. I look away from the telescope and see Perseus hanging them at the apex of the heavens. "If enough people wish for snow on Christmas day," he tells me, "their thoughts will shatter the crystal and the pieces will fall and turn to snow" As you can imagine, if snow did fall the next day I could see in it pieces of this shattered crystal glinting sharply in the morning light. It's not surprising that the Double Cluster could ignite a fire of imagination in a young skywatcher. Around the globe the great Double Cluster in Perseus is hailed as one of the most impressive telescopic sights in the heavens. Under dark skies the glow from this pair of stellar islands stretches across two Moon diameters and looks like a 4th-magnitude knot in the ruffled folds of the Milky Way, about halfway between Delta (δ) Cassiopeiae and Gamma (γ) Persei. Although Herschel is credited with discovering these objects' star-cluster nature, the combined glow of NGC 869 and NGC 884 has 14 been known since antiquity. Hipparchus recorded them as a "cloudy spot." In his book Star Names: Their Lore and Meaning, Richard Hinckley Allen says that Ptolemy noted them as a "dense mass," and subsequent pretelescopic astronomers saw them as nebulous entities. Allen also says that the twin clusters "seem strangely to have escaped the notice of astrologers, who, as a rule, devoted much attention to clusters as harmful objects which portended accidents to sight and blindness." Without the aid of a telescope, however, it's doubtful astrologers would have associated this "cloud" with an obvious cluster, such as the Pleiades. Today NGC 869 and 884 are simply known as the Double Cluster in the Sword Hand of Perseus. One long-lived mystery concerning the Double Cluster is why the 18th-century French comet hunter Charles Messier did not include it in his famous catalog. (Actually, Messier probably had a good reason not to do so; see Appendix Β for details). An equally compelling mystery is that, while Hipparchus and other early skywatchers listed NGC 869 and NGC 884 as two objects, few of today's amateurs seem to believe the components can be resolved with the unaided eye. Most popular astronomy books and articles state that the Double Cluster can be seen with the unaided eye only as a hazy patch of light, which becomes two beautiful objects with the aid of binoculars or a rich-field telescope. With a sweep of the hand that statement is true. But I wonder how many observers have missed seeing two distinct components with the unaided eye (not to mention the brightest stars superposed on them) because no one told them to look. Together the two clusters occupy a full degree of sky, and their bright cores are separated by 25' — nearly a full Moon diameter. Why, then, have these distinct cores escaped The Caldwell Objects 63
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DEEP-SKY COMPANIONS The Caldwell Ob
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DEEP-SKY COMPANIONS The Caldwell Ob
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Contents Foreword by Patrick Moore
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to be more difficult than others, s
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years of thought and observation ar
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XII position, type, angular size, a
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sky and share its splendors. There
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CHAPTER 1 About This Book O N ONE S
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times vog can back up and cause a s
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when there is moisture in the air.
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Herschel's original observations, p
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we use today and to one another? I
Page 29 and 30: SIMBAD (Set of identifications, Mea
Page 31 and 32: Caldwell 26. The objects in the Cal
Page 33 and 34: tion near the edges of the charts).
Page 35 and 36: nights of observing. Unless otherwi
Page 37 and 38: CHAPTER 2 The Caldwell Objects 1 1
Page 39 and 40: Because of its location far from th
Page 41 and 42: as strongly energized as would be e
Page 43 and 44: suggested by the patchiness of NGC
Page 45 and 46: 4 NGC 7023 Type: Reflection Nebula
Page 47 and 48: astronomers found direct evidence o
Page 49 and 50: and his contemporaries. Why then wa
Page 51 and 52: 6 Cat's Eye Nebula NGC 6543 Type: P
Page 53 and 54: Eighth-magnitude NGC 6543 is locate
Page 55 and 56: 7 NGC 2403 Type: Mixed Spiral Galax
Page 57 and 58: according to theory, the gas densit
Page 59 and 60: 8 Ghost’s Goblet NGC 559 Type: Op
Page 61 and 62: One other thing adds to the cluster
Page 63 and 64: RA: 22 h 56.8 m Dec: +62° 37' Mag:
Page 65 and 66: nebula is a near impossibility, eve
Page 67 and 68: 1 0 The Horseshoe Cluster NGC 663 T
Page 69 and 70: heart of the cluster, dividing it i
Page 71 and 72: appears to be the edge of a rapidly
Page 73 and 74: 1 2 NGC 6946 Type: Mixed Spiral Gal
Page 75 and 76: to the west by a row of similarly b
Page 77 and 78: the south-southwest. NGC 457, howev
Page 79: photographs. The cluster's bright "
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Page 87 and 88: 15 outer shell falls upon the retin
Page 89 and 90: "knots" have also been noted by exp
Page 91 and 92: tight gathering of a half-dozen rou
Page 93 and 94: 1 7 NGC 147 Type: Elliptical Galaxy
Page 95 and 96: the center. A faint outer halo is a
Page 97 and 98: 1 9 Cocoon Nebula IC 5146 (nebula)
Page 99 and 100: trickle into the pool surrounding t
Page 101 and 102: 2 0 North America Nebula NGC 7000 T
Page 103 and 104: egion's size and mass extreme when
Page 105 and 106: The Caldwell Objects 20 87
Page 107 and 108: 2 1 Box Galaxy NGC 4449 Type: Irreg
Page 109 and 110: fuse but obvious glow of patchy lig
Page 111 and 112: qualifier—the word "light" — ha
Page 113 and 114: with a sheen of light, especially a
Page 115 and 116: 1003, NGC 1023, and NGC 1058 (a nic
Page 117 and 118: Way) that pop in and out of view as
Page 119 and 120: RA: 03 h 19 m 48 s Dec: +41° 30.7'
Page 121 and 122: Through the 4-inch, NGC 1275 is les
Page 123 and 124: (300,000 light-years), Pal 4 (360,0
Page 125 and 126: 26 Silver Needle Galaxy NGC 4244 Ty
Page 127 and 128: 2 7 Crescent Nebula NGC 6888 Type:
Page 129 and 130: Observatory, England) still lists a
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pie refractors and inefficient spec
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29 NGC 5005 Type: Mixed Spiral Gala
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s h a edges. r p However, Christian
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ulars; challenge yourself and your
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NGC 7331 is extended much farther t
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away" stars escaped the confines of
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sweep the telescope in a north-sout
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highly suspect by some. However, in
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33 Network Nebula; Bridal Veil Nebu
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A quarter-second later, the star en
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under the dark skies of Seagrave Ob
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35 NGC 4889 Type: Elliptical Galaxy
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magnitude 12.2 some 18' to the east
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36 NGC 4559 Type: Mixed Spiral Gala
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Comae Berenices, the obvious northe
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3 7 NGC 6885 Type: Open Cluster Con
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pressed, stars of magnitude 6 to 11
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of Herschel's telescope. W then e e
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see the dark needle near the third
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sion of a "thin flat ring of enormo
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(which does not appear on Sky Atlas
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not be found in planetary nebulae,
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star in a large naked-eye triangle
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4 0 NGC 3626 Type: Lenticular Galax
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40 NGC 4546 in Virgo, NGC 4138 in C
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Northern Hemisphere, and people cel
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magnitude field star 2' to the nort
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this state of affairs.) The Hyades
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4 2 NGC 7006 Type: Globular Cluster
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each square arcminute of its disk s
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4 3 Electric Arc NGC 7814 Type: Spi
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hook as my "train route." Start at
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230 billion Suns and a physical dia
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4 5 NGC 5248 Type: Mixed Spiral Gal
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of the field. Those living under da
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1" in a mere four days. Clearly, La
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porarily) even the most practiced o
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stragglers are stars that appear to
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4 8 NGC 2775 Type: Spiral Galaxy (S
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with a CCD camera — discovered a
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this wreathlike network of dust and
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fuzzy patch of light with the unaid
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known as NGC 2244; and NGC 2239 sho
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At a glance the two stars at the cl
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On four plates taken with the Bruce
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years. A total of 43 star-cluster c
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5 2 NGC 4697 Type: Elliptical Galax
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northeast of the sixth star in the
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53 The Spindle NGC 3115 Type: Lenti
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and the 100-inch telescopes atop Mo
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emerge, followed by a diffuse outer
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perfection than is actually the cas
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jets, like a stream of water from t
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5 6 Pac-Man Nebula NGC246 Type: Pla
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the triple-alpha process, wherein t
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5 7 Barnard's Galaxy NGC 6822 Type:
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to show how the galaxy's western re
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core and limber arms, which, he wro
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esembles Jupiter . . . '" Smyth's f
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years" and suggests amateurs monito
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6 0 Ringtail Galaxy; Rataail Galaxy
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war. X-ray images taken by the Rosa
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W. Sinnott's NGC 2000.0 has a visua
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62 Milkweed Seed Galaxy NGC247 Type
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through the narrow haze. But give t
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was more readily seen in binoculars
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Society. Accepting that distance, w
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any large telescope that can provid
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ought it to our attention in the Fe
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inch the cluster shows a pyramid of
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NGC 253 is the brightest member of
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magnitude stars, one just to the ea
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6 6 NGC5694 Type: Globular Cluster
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you see its core dancing? Its starl
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cosmologist Halton Arp (Max-Planck
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and kinked. All this detail is wrap
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telescope. But seeing it takes more
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streamers begin to appear, but they
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tounding, because NGC 6302 is a mag
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70 Southern Pinwheel NGC300 Type: S
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would John Herschel suddenly fault
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Dunlop discovered NGC 55 with his 9
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even when crossing the meridian. Co
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"nebulous clusters" (Class II); and
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galaxy's disk and halo. NGC 2477 ap
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condensed, almost to the very margi
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The asymmetry remains at high power
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other popular nickname, the Eight-B
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longed look, the object displays a
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times larger than the full Moon. In
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emains of a globular cluster that w
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he classified them accordingly. NGC
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NGC 6231). Under averted vision the
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7 7 Centaurus A NGC5128 Type: Pecul
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Harvard College Observatory's 24-in
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at 16 million light-years. If you s
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78 NGC 6541 Type: Globular Cluster
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seems to fragment into tiny stars,
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sense, evinced by any known cluster
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12th-magnitude double star. The clu
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original with Bayer, but goes back
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Omega Centauri is generally regarde
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glitter all come to mind as the clu
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shattered remains of their diminuti
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It's a nice even disk of l0th-magni
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with the fiery reddish light of hyd
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nebulosity when he viewed the regio
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the two jets of radio-wave-emitting
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pair of tweezers. A fairly bright s
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suggest that our universe may be on
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8 5 Omicron Velorum Cluster IC2391
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Nicolas Louis de Lacaille, however,
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much sky as does the full Moon, tho
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timates, making it 2 billion years
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NGC 5822. Don't be surprised if you
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89 S Normae Cluster NGC 6087 Type:
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fact, if you look about 7' southwes
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lowing night fell clear, when Hersc
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NGC 2867 is a nitrogen-rich planeta
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halfway between M37 in Auriga (200
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9 2 Eta Carinae Nebula GC 3372 Type
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anch of cold, dark material. Indeed
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stretch 16 billion km from the cent
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the object was known to some civili
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east, and a dim lip of gas to the s
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1 0 1 NGC 6744 Type: Barred Spiral
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have been identified in NGC 6752's
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ightest spiral arm(s) to the north,
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his maiden voyage of discovery in 1
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simply takes much too much effort t
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very wide double of near-equal inte
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went out and looked at the cluster
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NGC 2516 is 60 million years young
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and contains some 1,890 members, wh
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9 8 Coalsack Cluster NGC 4609 Type:
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it near the Swan? There is a still
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with the naked eye is a challenge.
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1 0 0 Lambda Centauri Cluster Colli
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position updates to (2000.0) R.A. 1
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Eta Carinae Nebula. But remember th
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9th magnitude. Of the latter, 23 ha
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103 1 0 3 Tarantula Nebula; True Lo
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southern-sky explorer Abbe Nicolas
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ters it has had thus far with the g
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ly east of NGC 362 we find the magn
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the eye ever inward and takes your
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1 0 5 Southern Butterfly NGC 4833 T
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stars"). Lacaille also likened NGC
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is about 7' in length, and nearly 2
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evealed a significant blue-straggle
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ightest stars shine around 4th magn
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egion looks cold and disturbing, no
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The galaxy received some incidental
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This entry is obviously in error, b
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7 N G C 4 0 4 T y L p e n : G t a i
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pointed her 7x35 binoculars toward
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13 NGC 288 Type: Globular Cluster C
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your telescope on Eta Sculptoris an
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19 N G C 6 2 8 1 T y O p e C : n l
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C Name Type Con. R.A. Dec Mag. Size
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C Name Type Con. R.A. Dec Mag. Size
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Appendix B Why Messier Did N o t i
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A typical pattern for evening hunti
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Earth turns, the cluster would clim
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Initially Herschel made his living
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of the heavens with it. For his swe
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tube's front end. This meant that t
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Star in Collo Ceti" about the star
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years, Herschel would observe some
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fluid, but added that ages of obser
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Appendix D Photo Credits in order o
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A Abell426, 101 Acrux, 388, 392, 39
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index Caldwell 44, 173, 176-178 Cal
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and nebulae, 271, 274, 362 and open
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Hevelius, Johannes, 72, 81, 452 Hip
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M103, 49-50, 58-59 M110, 77 MACHOs.
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NGC 3324, 369 NGC 3372 (Caldwell 92
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Perseus Cluster, 101 Phi Cas Cluste
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Τ Tarantula Nebula (Caldwell 103),
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The Caldwell Objects

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