Celestial Atlas
Caldwell Objects Not In The NGC/IC

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Page last updated Sep 13, 2023

C9, the Cave Nebula
(= Sh2-155 = Sharpless 155)

First noted (1959) as a galactic emission nebula in the extended second edition of the Sharpless Catalogue
A magnitude 7.7 emission nebula in Cepheus (RA 22 57 17.1, Dec +62 28 33)
Note About The Nickname: The nickname was coined by Patrick Moore, "presumably derived from photographic images showing a curved arc of emission nebulosity" obscured by a foreground absorption nebula "corresponding to a cave mouth." Unfortunately, that appellation had been previously assigned to a brighter reflection nebula (also in Cepheus but unrelated to C9) known as Ced 201, and as a result, SIMBAD returns a search for the Cave Nebula with Ced 201, instead of Caldwell 9.
(Physical information and other images to be posted once all Caldwell objects have been added to this Catalog.)
HST image of Caldwell 9Above, a ? arcmin wide HST image of C9
(Image Credit NASA, ESA, and K. Stapelfeldt (Jet Propulsion Laboratory); Processing: Gladys Kober (NASA/Catholic University of America)
(Note: The 'palette' used for this image is not the "standard" HST palette, so the colors are very different from other images of the nebula)

C41, the Hyades
(= Cr 50 = Mel 25)

Known in prehistory
Catalogued (1654) by Giovanni Hodierna
A magnitude 0.5 open cluster in Taurus (RA 04 27, Dec +15 52)
Physical Information: Shown to consist of stars moving together in the 1800's, and currently thought to have a common origin with the open cluster known as Praesepe, around 625 million years ago. (Additional physical information and other images to be posted once all Caldwell objects have been added to this Catalog.
DSS image of region near the Hyades
Above, a 5 degree wide DSS image of the Hyades (most of the blue stars; the yellow star Aldebaran is a foreground object)

C99, the Coalsack Nebula
Noted by several southern civilizations in prehistoric times
Reported (1499) by Spanish navigator Vicente Yáñez Pinzón
Also noted (date?) by Amerigo Vespucci
Modern name acquired (1899) due to Richard Hinckley Allen naming a northern absorption nebula
An absorption cloud primarily located in Crux (roughly centered near RA 12 50, Dec -62 30)
Historical References: Among the Australian aborigines, who like many primitive cultures used dark regions in the Milky Way as constellations, it was known as the head of the "emu in the sky". Vespucci referred to it as "the dark Canopus". It later became known as "Magellan's Spot", or the "Black Magellanic Cloud", as opposed to the bright Large and Small Magellanic Clouds (which are of course galaxies, and not part of the Milky Way). The term "coalsack" was long used for any dark region in the Milky Way, and what we now call the Coalsack Nebula only became the Coalsack Nebula in 1899, when Richard Hinckley Allen's Star-Names and Their Meaning (later republished as Star-Names -- Their lore and meaning) assigned "The Northern Coalsack Nebula" to an absorption feature in the Northern sky.
Physical Information: The nebula is a cloud of gas and dust less than 600 light-years from us, and although only about 30 to 35 light-years in size, its close proximity allows it to obscure a region about 7 by 5 degrees across, covering not only part of Crus, but also parts of Centaurus and Musca. It is slightly patchy, and although covering almost everything lying beyond it, there are places where more distant objects can be seen, and of course anything closer than the absorption nebula is also visible. Still, it is a very obvious and striking blot on the starry background of the Milky Way.
ESO image of the Southern Cross and the Coalsack Nebula
Above, a 10 by 12 degree wide ESO image of the Southern Cross and the Coalsack Nebula
Part of an image of Crux (Image Credit ESO, Brunier)
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