The Caldwell Objects

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40 Now, if you push your telescope 35' due east of the center point between NGC 3607 and 3608, you will encounter a 10th-magnitude star. NGC 3626 sits alone just about 15' northeast of that star. NGC 3626 is only 0.2 magnitude (20 percent) fainter than NGC 3608, so look for something similarly bright when you search for the Caldwell galaxy. NGC 3626 is inclined 48° from face on. With the 4-inch at 23x and averted vision it looks like a slightly out-of-focus star south of a flattened keystone of dim suns. (With direct vision the galaxy just looks like another star.) Lenticular galaxies are known for being small and bright, packing a lot of light into their lens-shaped bodies. NGC 3626 is no exception, though its distance places it at a disadvantage. The galaxy is three and a half times farther from Earth than Leo's celebrated M65. If NGC 3626 were at M65's distance it would blaze at magnitude 8.3 (a full magnitude brighter than M65) and be a truly stunning sight, even outperforming the lenticular wonder NGC 5866 in Draco (see page 432). NGC 3626 is a large system, with a physical diameter of 70,000 light-years and a total mass of 120 billion Suns. Alas, even at 130x the galaxy shows very little detail in the 4-inch. A dim outer halo surrounds a brighter lens-shaped oval that hugs the galaxy's needle-sharp nucleus. With a long, intense look I convinced myself that the inner lens's light distribution is not entirely uniform, though the slight intensity differences are fleeting at best. If yours is a small telescope, do not fret. Most lenticular galaxies are notoriously bland. Even with her 20-inch reflector Barbara Wilson saw no outstanding details in NGC 3626. Indeed, even in the plates taken with the 48-inch Schmidt telescope atop Palomar Mountain (one of which is reproduced on page 159), the galaxy looks like three gray ovals of varying intensity superimposed on one 160 another; the brightest oval is skewed counterclockwise with respect to the smooth, symmetrical outer envelope. CCD images can penetrate the core that so often is burned out in photographs, and they reveal a pinpoint nucleus as well as a suggestive hint of obscuring dust in the eastern half of the inner lens. In a 1998 Astrophysical Journal paper, Daniela Bettoni (Astronomical Observatory of Padova, Italy) and her colleagues reported a massive counter-rotating disk of molecular gas in NGC 3626. The gas is swimming against the tide, so to speak, of the stars in the galaxy's disk. This finding is not unprecedented. In 1992 Vera Rubin (Carnegie Institute of Washington) discovered that almost half of the stars in the disk of Virgo's NGC 4550 were orbiting in the direction opposite that of the galaxy's other stars. In other words, NGC 4550 appears to contain two disks, one spinning clockwise as seen from Earth, the other counterclockwise. (Anyone who has been to the Vatican will appreciate this discovery, for the Vatican has an intricate double-spiral staircase in which ascending visitors never meet descending ones, even though the spirals are concentric.) Other galaxies that show this cospatial counterrotation are NGC 4826 in Coma Berenices, NGC 7217 and NGC 7332 in Pegasus, Deep-Sky Companions: The Caldwell Objects
40 NGC 4546 in Virgo, NGC 4138 in Canes Venatici, and NGC 3593 in Leo. How can a galaxy possess two disks with opposite angular momenta? NGC 3626's undisturbed morphology rules out a recent, disruptive merger between two spiral galaxies with opposite spins. But the counter-rotating gas might have been acquired gradually from the detritus of previous interactions. If the inwardfalling material's orbit around the mass-gaining galaxy opposes that of the galaxy's preexisting disk, a counter-rotating structure is formed. The Caldwell Objects 161
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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
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SIMBAD (Set of identifications, Mea
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Caldwell 26. The objects in the Cal
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tion near the edges of the charts).
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nights of observing. Unless otherwi
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CHAPTER 2 The Caldwell Objects 1 1
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Because of its location far from th
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as strongly energized as would be e
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suggested by the patchiness of NGC
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4 NGC 7023 Type: Reflection Nebula
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astronomers found direct evidence o
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and his contemporaries. Why then wa
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6 Cat's Eye Nebula NGC 6543 Type: P
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Eighth-magnitude NGC 6543 is locate
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7 NGC 2403 Type: Mixed Spiral Galax
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according to theory, the gas densit
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8 Ghost’s Goblet NGC 559 Type: Op
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One other thing adds to the cluster
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RA: 22 h 56.8 m Dec: +62° 37' Mag:
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nebula is a near impossibility, eve
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1 0 The Horseshoe Cluster NGC 663 T
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heart of the cluster, dividing it i
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appears to be the edge of a rapidly
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1 2 NGC 6946 Type: Mixed Spiral Gal
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to the west by a row of similarly b
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the south-southwest. NGC 457, howev
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photographs. The cluster's bright "
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play begins at 8:00 p.m., when my e
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ightness by summing the contributio
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jewels. Here are sapphires, rubies,
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15 outer shell falls upon the retin
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"knots" have also been noted by exp
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tight gathering of a half-dozen rou
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1 7 NGC 147 Type: Elliptical Galaxy
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the center. A faint outer halo is a
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1 9 Cocoon Nebula IC 5146 (nebula)
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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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Page 129 and 130: Observatory, England) still lists a
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Page 133 and 134: 29 NGC 5005 Type: Mixed Spiral Gala
Page 135 and 136: s h a edges. r p However, Christian
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Page 139 and 140: NGC 7331 is extended much farther t
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Page 145 and 146: highly suspect by some. However, in
Page 147 and 148: 33 Network Nebula; Bridal Veil Nebu
Page 149 and 150: A quarter-second later, the star en
Page 151 and 152: under the dark skies of Seagrave Ob
Page 153 and 154: 35 NGC 4889 Type: Elliptical Galaxy
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Page 161 and 162: 3 7 NGC 6885 Type: Open Cluster Con
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Page 177: 4 0 NGC 3626 Type: Lenticular Galax
Page 181 and 182: Northern Hemisphere, and people cel
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Page 187 and 188: 4 2 NGC 7006 Type: Globular Cluster
Page 189 and 190: each square arcminute of its disk s
Page 191 and 192: 4 3 Electric Arc NGC 7814 Type: Spi
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Page 197 and 198: 4 5 NGC 5248 Type: Mixed Spiral Gal
Page 199 and 200: of the field. Those living under da
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Page 205 and 206: 4 7 NGC 6934 Type: Globular Cluster
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Page 209 and 210: 4 8 NGC 2775 Type: Spiral Galaxy (S
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Page 219 and 220: At a glance the two stars at the cl
Page 221 and 222: On four plates taken with the Bruce
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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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5 4 NGC 2506 Type: Open Cluster Con
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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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8 7 NGC 1261 Type: Globular Cluster
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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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