The Caldwell Objects

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5 their full extent as seen in photographs. Hints of tangential spiral filaments could also be gleaned, though the reality of those features remains uncertain; the eye tends to follow chains of faint stars, tricking observers into believing they are seeing coherent extragalactic structures. Although faint, the spiral structure in IC 342 is much easier to trace than that in either M74 orMlOl. IC 342 is a close neighbor of the Milky Way, cosmologically speaking; it resides only 13 million light-years away — 19 million light-years closer than M74 and 4.5 million light-years closer than Μ101. IC 342 is inclined at an angle of about 20° from face on. It measures 61,000 light-years in diameter and is receding from the solar system at a cosmologically negligible speed of 32 km per second. The galaxy belongs to the Coma-Sculptor Cloud and trav- els through space with NGC 2403 (Caldwell 7), NGC 6946 (Caldwell 12), and NGC 147 and NGC 185 (Caldwell 17 and 18, respectively). IC 342 is a starburst galaxy of sorts. Its nucleus contains a cluster of hot, 10-million-yearyoung supergiant stars, each with a mass between 12 to 18 Suns. This cluster is surrounded by a gaseous star-forming ring about 230 lightyears in diameter. Intense star formation is happening in two giant Η II regions roughly 4" to either side (east and west) of the nucleus. These regions are similar to "super-clusters" like 30 Doradus in the Large Magellanic Cloud (see Caldwell 103) and are only about 5 million years old. The sweeping motion of an inner bar structure could be triggering these starbursts as it moves through molecular clouds populating the inner regions of IC 342. 32 Deep-Sky Companions: The Caldwell Objects
6 Cat's Eye Nebula NGC 6543 Type: Planetary Nebula Con: Draco RA: 17 h 58 m 33.4 s Dec: +66° 37' 59" Mag: 8.1 Dim: 23" x 17" Dist: ~3,000 light-years Disc: William Herschel, 1786 W . HERSCHEL: [Observed 15 February 1786] A planetary nebula. Very bright. Has a disk of about 35" diameter, very ill-defined edge. With long attention a very bright well defined round center becomes visible. (H IV-37) BY AREA, DRACO RANKS EIGHTH AMONG THE 88 constellations, containing 1,083 square degrees of sky within its long, zigzagging borders. Despite its generous size, Draco possesses only one noteworthy planetary nebula: NGC 6543, commonly called the "Cat's Eye." Jay McNeil, a planetary-nebula aficionado from Kingwood, Texas, rates NGC 6543 as one of the best of the night sky's bright planetaries. William Herschel is often credited with naming these curious objects "planetary nebulae" in 1785 because their round forms resembled that of the pale green planet (Uranus) he discovered four years earlier. But French astronomer Antoine Darquier de Pellepoix also deserves credit; in 1779 Darquier de Pellepoix discovered the famous Ring Nebula (M57) in Lyra and likened its appearance to a "fading planet." At the time, most observers believed these objects to be masses of unresolved stars rather than gaseous nebulae. The first clue to their true nature came on August 29,1864, when English amateur astronomer William Huggins turned The Caldwell Objects GC / NGC: Planetary nebula, very bright, pretty small in angular size, suddenly brighter in the middle to a very small nucleus. 6 a spectroscope to NGC 6543; it was the first nebula of its kind to be studied this way. Huggins immediately recognized that the spectrum he saw was that of a luminous gas, not a haze of unresolved suns. Today we know planetary nebulae are indeed thick shells of gas ejected by, and moving out from, the extremely hot cores of dying red-giant stars. Such activity portends the fate of our Sun. On January 11, 1995, the Space Telescope Science Institute introduced the Cat's Eye to the public eye. Magazines, newspapers, and calendars soon carried stunning HST images of NGC 6543. Ground-based images, like that above, merely show the planetary's bright central star seemingly tied in a loose knot of overlapping gas shells. But HST's powerful eye added depth to the scene, revealing a three-dimensional tangle of loops, bubbles, and jets. Apparently the nebula's innermost structure is an oblong bubble of gas blown out at supersonic speeds from what is now suspected to be a binary central star; the ends of this bubble seem to have burst open. The elongated central bubble 33
Page 5 and 6: DEEP-SKY COMPANIONS The Caldwell Ob
Page 7 and 8: DEEP-SKY COMPANIONS The Caldwell Ob
Page 9 and 10: Contents Foreword by Patrick Moore
Page 11 and 12: to be more difficult than others, s
Page 13 and 14: years of thought and observation ar
Page 15 and 16: XII position, type, angular size, a
Page 17 and 18: sky and share its splendors. There
Page 19 and 20: CHAPTER 1 About This Book O N ONE S
Page 21 and 22: times vog can back up and cause a s
Page 23 and 24: when there is moisture in the air.
Page 25 and 26: Herschel's original observations, p
Page 27 and 28: 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 his contemporaries. Why then wa
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 and 80: photographs. The cluster's bright "
Page 81 and 82: play begins at 8:00 p.m., when my e
Page 83 and 84: ightness by summing the contributio
Page 85 and 86: jewels. Here are sapphires, rubies,
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
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2 0 North America Nebula NGC 7000 T
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egion's size and mass extreme when
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The Caldwell Objects 20 87
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2 1 Box Galaxy NGC 4449 Type: Irreg
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fuse but obvious glow of patchy lig
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qualifier—the word "light" — ha
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with a sheen of light, especially a
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1003, NGC 1023, and NGC 1058 (a nic
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Way) that pop in and out of view as
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RA: 03 h 19 m 48 s Dec: +41° 30.7'
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Through the 4-inch, NGC 1275 is les
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(300,000 light-years), Pal 4 (360,0
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26 Silver Needle Galaxy NGC 4244 Ty
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2 7 Crescent Nebula NGC 6888 Type:
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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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