The Caldwell Objects

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51 5 1 The Scarecrow IC 1613 Type: Irregular Barred Dwarf Galaxy (IBm) Con: Cetus RA:01 h 04.8 m Dec: +02° 07' Mag: 9.2 Dim: 18.8' x 17.3' SB: 15.5 Dist: 2.3 million light-years Disc: Max Wolf, 1906 H ERSCHEL: None. GC: None. IC: Faint, most extremely large. T HE IRREGULAR DWARF GALAXY IC 1613 (Caldwell 51) is the most challenging object to see in the Caldwell Catalog. It hides in the northwestern quadrant of Cetus, just ½° south of the Pisces border, where it escaped detection until Max Wolf discovered it photographically in 1906 with the Bruce 16-inch refractor at the Astrophysical Observatory in Heidelberg, Germany. Dating this important discovery was somewhat of a chore. The Index Catalogues credit Wolf with the discovery but do not provide a date or any references. Having exhausted some other resources, I turned the problem over to Brent Archinal, who ran up against the same wall. Archinal recruited the help of Harold Corwin, who also came up empty handed. But Corwin did suspect we'd find the discovery in the journal Astronomische Nachrichten. Archinal followed Corwin's advice and checked that journal's indexes covering dates from 1895 to 1908 (Sidney van den Bergh had noted in Astronomy & Astrophysics Review that IC 1613 was known in 1907). One of the last papers Archinal looked at appeared in the October 17, 1907, Astronomische Nachrichten. It was a paper by Wolf entitled "Ein Nebelfleckhaufen und Nebelreichtum in Sagittarius." It described what Wolf thought were some unusual patches of nebulosity in Sagittarius. "It turns out," Archinal says, "that these patches of nebulosity are obviously Barnard's Galaxy (NGC 6822) [Caldwell 57]. More importantly this paper compares these patches to a nebula near 26 Ceti discovered earlier by Wolf, and reported in the November 9, 1906, Monthly Notices of the Royal Astronomical Society." Sure enough, in the Monthly Notices letter — "Extended Nebula near 26 Ceti" — Wolf announces his discovery of what we now call IC 1613: 202 Deep-Sky Companions: The Caldwell Objects
On four plates taken with the Bruce 16-inch telescope in September I find an extended nebula, which attracts attention both by its situation and its appearance. Practically all extended nebulosities are found in or near the Milky-way, but this object is about 70° distant from the plane of the Milky-way. Its densest part is situated at [RA] = 0 h 57 m .4 [Dec] = + 1° 20' (1855.0) Round this is spread faint nebulous matter of varying intensity. At several points small clouds of greater density shine forth. Further out, the intensity is so feeble that it is impossible to exactly define its limits. It seems that these will be materially altered by lengthening the exposure. My exposures extend to four hours. With these the nebulous cloud extends about 40' in declination and about 30' in R.A. [Three] B.D. stars [whose positions are given here] are all involved in the cloud. Southwards it reaches nearly to the B.D. star + 0°.207 0h56m.9 +1° 0' but it cannot be certainly detected up to the star. Especially towards the west the nebulous matter promises to go much further. Under the microscope the brighter parts of the mass are filled with numerous very small spots and short trails, so that the appearance is very different from that presented by the Milky-way nebulae. It seems possible that this object is a multitude of very small planetary nebulae collected in a cluster, which a more powerful instrument than mine may perhaps resolve. Astrophysical Observatory, Heidelberg: 1906 October. Archinal updated to equinox 2000.0 the positional information supplied by Wolf and The Caldwell Objects 51 discovered that Wolf's position for the galaxy "was off." He also noticed that the size listed in table on page 202 (18.8' x 17.3') is noticeably smaller than Wolf's estimate of 40' x 20'. "Did Wolf's exposure go so deep that it showed outer regions not indicated by the size in modern catalogues?" Archinal asks. "Is that why his position is off? It is also interesting that [Wolf] describes what are (now) obviously lots of Η II regions within the galaxy." That Messier and the Herschels failed to spot this loose assemblage of dim suns is not surprising. Although IC 1613 shines at 9th magnitude, its integrated brightness is deceiving. The galaxy's light is spread across an area of sky about the size of a quarter Moon, so each square arcminute of its surface shines with an apparent magnitude of 15.5 — more than six times fainter than Pluto's maximum brightness. This breath of extragalactic light was far beyond the visual grasp of Messier and his contemporaries, and it was too dim and large for the powerful but narrow-field Herschel telescopes. Many amateur astronomy guides pass over IC 1613, claiming it is too dim and difficult for amateur telescopes, but this is not necessarily the case. Before delving into that controversy, let's first look at the wonder of this tiny system, which astronomers often refer to as the dimmest member of our Local Group of galaxies. IC 1613 lies 2.3 million light-years distant, so it is as far as M31, the Great Andromeda galaxy. It measures 12,400 light-years across, which is comparable to the sizes of NGC 147 and 185 (Caldwell 17 and 18), two of the dwarfs attending M31. But the Andromeda dwarfs are much easier than IC 1613 to see, because they have higher surface brightnesses. IC 1613 has the intrinsic luminosity of a mere 80 million Suns, making it one of the least luminous galaxies known. Like the Andromeda dwarfs, IC 203
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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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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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Page 177 and 178: 4 0 NGC 3626 Type: Lenticular Galax
Page 179 and 180: 40 NGC 4546 in Virgo, NGC 4138 in C
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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
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Page 219: At a glance the two stars at the cl
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Page 225 and 226: 5 2 NGC 4697 Type: Elliptical Galax
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Page 229 and 230: 53 The Spindle NGC 3115 Type: Lenti
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Page 241 and 242: 5 6 Pac-Man Nebula NGC246 Type: Pla
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Page 245 and 246: 5 7 Barnard's Galaxy NGC 6822 Type:
Page 247 and 248: to show how the galaxy's western re
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Page 251 and 252: core and limber arms, which, he wro
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Page 265 and 266: through the narrow haze. But give t
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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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9 5 NGC 6025 Type: Open Cluster Con
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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),
show all

The Caldwell Objects

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