Caldwell catalogue

The Caldwell catalogue is an astronomical catalogue of 109 star clusters, nebulae, and galaxies for observation by amateur astronomers. The list was compiled by Patrick Moore as a complement to the Messier catalogue.[1]

While the Messier catalogue is used by amateur astronomers as a list of deep-sky objects for observation, Moore noted that Messier's list was not compiled for that purpose and excluded many of the sky's brightest deep-sky objects,[1] such as the Hyades, the Double Cluster (NGC 869 and NGC 884), and the Sculptor Galaxy (NGC 253). The Messier catalogue was actually compiled as a list of known objects that might be confused with comets. Moore also observed that since Messier compiled his list from observations in Paris, it did not include bright deep-sky objects visible in the Southern Hemisphere, such as Omega Centauri, Centaurus A, the Jewel Box, and 47 Tucanae.[1][2] Moore compiled a list of 109 objects to match the commonly accepted number of Messier objects (he excluded M110[3]), and the list was published in Sky & Telescope in December 1995.[3]

Moore used his other surname – Caldwell – to name the list, since the initial of "Moore" is already used for the Messier catalogue.[1][4] Entries in the catalogue are designated with a "C" and the catalogue number (1 to 109).

Unlike objects in the Messier catalogue, which are listed roughly in the order of discovery by Messier and his colleagues,[5] the Caldwell catalogue is ordered by declination, with C1 being the most northerly and C109 being the most southerly,[1] although two objects (NGC 4244 and the Hyades) are listed out of sequence.[1] Other errors in the original list have since been corrected: it incorrectly identified the S Norma Cluster (NGC 6087) as NGC 6067 and incorrectly labelled the Lambda Centauri Cluster (IC 2944) as the Gamma Centauri Cluster.[1]

Caldwell catalogue
Caldwell Catalogue
Montage of Caldwell Catalogue objects.

Caldwell star chart

Caldwell Star Chart

Number of objects by type in the Caldwell catalogue

Dark nebulae 1
Galaxies 35
Globular clusters 18
Nebulae 9
Star clusters 25
Star clusters and nebulae 6
Planetary nebulae 13
Supernova remnants 2
Total 109

Caldwell objects

  Star cluster   Nebula   Galaxy

Caldwell number NGC number Common name Picture Type Distance
(1000 ly)
Constellation Magnitude
C1 NGC 188   NGC 188 Open Cluster 4.8 Cepheus 8.1
C2 NGC 40 Bow-Tie Nebula Ngc40 Planetary Nebula 3.5 Cepheus 11
C3 NGC 4236   NGC 4236 I FUV g2006 Barred Spiral Galaxy 7,000 Draco 9.7
C4 NGC 7023 Iris Nebula N7023 Open Cluster and Nebula 1.4 Cepheus 7
C5 IC 342   IC 342 Spiral Galaxy 10,000 Camelopardalis 9
C6 NGC 6543 Cat's Eye Nebula Cat's Eye Nebula Planetary Nebula 3 Draco 9
C7 NGC 2403   NGC2403-SN2004dj Spiral Galaxy 14,000 Camelopardalis 8.4
C8 NGC 559   NGC 559 Open Cluster 3.7 Cassiopeia 9.5
C9 Sh2-155 Cave Nebula Cave Nebula Nebula 2.8 Cepheus 7.7
C10 NGC 663   NGC663HunterWilson Open Cluster 7.2 Cassiopeia 7.1
C11 NGC 7635 Bubble Nebula NGC 7635HSTFull Nebula 7.1 Cassiopeia -
C12 NGC 6946 Fireworks Galaxy SpiralGalaxy NGC6946 Spiral Galaxy 18,000 Cepheus 8.9
C13 NGC 457 Owl Cluster, E.T. Cluster NGC457 Open Cluster - Cassiopeia 6.4
C14 NGC 869 & NGC 884 Double Cluster, H & χ Persei NGC869NGC884 Open Cluster 7.3 Perseus 4
C15 NGC 6826 Blinking Planetary NGC 6826HSTFull Planetary Nebula 2.2 Cygnus 10
C16 NGC 7243   NGC 7243 Open Cluster 2.5 Lacerta 6.4
C17 NGC 147   NGC 0147 2MASS Dwarf Spheroidal Galaxy 2,300 Cassiopeia 9.3
C18 NGC 185   Ngc185 Dwarf Spheroidal Galaxy 2,300 Cassiopeia 9.2
C19 IC 5146 Cocoon Nebula Cocoonhunter2 Open Cluster and Nebula 3.3 Cygnus 7.2
C20 NGC 7000 North America Nebula Nord america Nebula 1.8 Cygnus 4
C21 NGC 4449   Starburst in NGC 4449 (captured by the Hubble Space Telescope) Irregular galaxy 10,000 Canes Venatici 9.4
C22 NGC 7662 Blue Snowball Ngc7662hst Planetary Nebula 3.2 Andromeda 9
C23 NGC 891   NGC891HunterWilson Spiral Galaxy 31,000 Andromeda 10
C24 NGC 1275 Perseus A NGC1275 (1) Type-cD galaxy 230,000 Perseus 11.6
C25 NGC 2419   NGC 2419 Hubble WikiSky Globular Cluster 275 Lynx 10.4
C26 NGC 4244   NGC4244 Spiral Galaxy 10,000 Canes Venatici 10.2
C27 NGC 6888 Crescent Nebula NGC 6888HSTfull Nebula 4.7 Cygnus 7.4
C28 NGC 752   Ngc 752 Open Cluster 1.2 Andromeda 5.7
C29 NGC 5005   NGC5005 Spiral Galaxy 69,000 Canes Venatici 9.8
C30 NGC 7331   NGC 7331 zoomed Spiral Galaxy 47,000 Pegasus 9.5
C31 IC 405 Flaming Star Nebula FlamingStarHunterWilson Nebula 1.6 Auriga -
C32 NGC 4631 Whale Galaxy Whalegalaxy Barred Spiral Galaxy 22,000 Canes Venatici 9.3
C33 NGC 6992 East Veil Nebula Veil Nebula 800x600 Supernova Remnant 2.5 Cygnus -
C34 NGC 6960 West Veil Nebula WestVeilHunterWilson Supernova Remnant 2.5 Cygnus -
C35 NGC 4889   Ssc2007-10a1 Type-cD galaxy 300,000 Coma Berenices 11.4
C36 NGC 4559   NGC 4559 I FUV g2006 Spiral Galaxy 32,000 Coma Berenices 9.9
C37 NGC 6885   NGC 6885 Open Cluster 1.95 Vulpecula 6
C38 NGC 4565 Needle Galaxy Ngc 4565pg Spiral Galaxy 32,000 Coma Berenices 9.6
C39 NGC 2392 Eskimo Nebula/Clown Face Nebula Ngc2392 Planetary Nebula 4 Gemini 10
C40 NGC 3626 NGC 3626 SDSS Spiral Galaxy 86,000 Leo 10.9
C41 Mel 25 Hyades Hyades Open Cluster 0.151 Taurus 0.5
C42 NGC 7006   NGC7006 Globular Cluster 135 Delphinus 10.6
C43 NGC 7814   NGC7814HunterWilson Spiral Galaxy 49,000 Pegasus 10.5
C44 NGC 7479   Ngc7479 Barred Spiral Galaxy 106,000 Pegasus 11
C45 NGC 5248   Ngc5248-hst-R814G547B336 Spiral Galaxy 74,000 Boötes 10.2
C46 NGC 2261 Hubble's Variable Nebula Ngc2261 Nebula 2.5 Monoceros -
C47 NGC 6934   NGC 6934 Hubble WikiSky Globular Cluster 57 Delphinus 8.9
C48 NGC 2775   NGC2775-hst-R814GB450 Spiral Galaxy 55,000 Cancer 10.3
C49 NGC 2237 Rosette Nebula Rosette Nebula NGC 2237 - C49 Nebula 4.9 Monoceros 9.0
C50 NGC 2244   Ngc2244 Open Cluster 4.9 Monoceros 4.8
C51 IC 1613   IC1613-3 Irregular galaxy 2,300 Cetus 9.3
C52 NGC 4697     Elliptical galaxy 76,000 Virgo 9.3
C53 NGC 3115 Spindle Galaxy NGC 3115 2MASS Lenticular Galaxy 22,000 Sextans 9.2
C54 NGC 2506     Open Cluster 10 Monoceros 7.6
C55 NGC 7009 Saturn Nebula Ngc7009 hst big Planetary Nebula 1.4 Aquarius 8
C56 NGC 246   NGC 246 Planetary Nebula 1.6 Cetus 8
C57 NGC 6822 Barnard's Galaxy NGC6822 Barred irregular galaxy 2,300 Sagittarius 9
C58 NGC 2360   NGC 2360 in CMa Open Cluster 3.7 Canis Major 7.2
C59 NGC 3242 Ghost of Jupiter Ngc3242a Planetary Nebula 1.4 Hydra 9
C60 NGC 4038 Antennae Galaxies Antennae.jpeg Galaxy 83,000 Corvus 10.7
C61 NGC 4039 Antennae Galaxies Antennae galaxies xl Interacting galaxy 83,000 Corvus 13
C62 NGC 247   Ngc247 Spiral Galaxy 6,800 Cetus 8.9
C63 NGC 7293 Helix Nebula NGC 7293 Planetary Nebula 0.522 Aquarius 7.3
C64 NGC 2362   NGC 2362 NASA Open Cluster and Nebula 5.1 Canis Major 4.1
C65 NGC 253 Sculptor Galaxy Ngc253 2mass barred spiral Galaxy 9,800 Sculptor 7.1
C66 NGC 5694     Globular Cluster 113 Hydra 10.2
C67 NGC 1097   Ngc1097atlas Galaxy 47,000 Fornax 9.3
C68 NGC 6729 R CrA Nebula NGC 6729 Nebula 0.424 Corona Australis -
C69 NGC 6302 Bug Nebula NGC 6302 Hubble 2009.full Planetary Nebula 5.2 Scorpius 13
C70 NGC 300   Composite Image of NGC 300 Galaxy 3,900 Sculptor 9
C71 NGC 2477   NGC2477 Open Cluster 3.7 Puppis 5.8
C72 NGC 55   Spiral Galaxy NGC 55 Galaxy 4,200 Sculptor 8
C73 NGC 1851   PIA07908 Globular Cluster 39.4 Columba 7.3
C74 NGC 3132 Eight Burst Nebula NGC 3132 Planetary Nebula 2 Vela 8
C75 NGC 6124   NGC 6124 Open Cluster 1.5 Scorpius 5.8
C76 NGC 6231   NGC 6231 Open Cluster and Nebula 6 Scorpius 2.6
C77 NGC 5128 Centaurus A Centaurus A Galaxy 16,000 Centaurus 7
C78 NGC 6541   NGC 6541 Globular Cluster 22.3 Corona Australis 6.6
C79 NGC 3201   NGC 3201 Hubble WikiSky Globular Cluster 17 Vela 6.8
C80 NGC 5139 Omega Centauri STSci-PRC01-33 omega centauri Globular Cluster 17.3 Centaurus 3.7
C81 NGC 6352   NGC 6352 Globular Cluster 18.6 Ara 8.2
C82 NGC 6193   Rgb-ngc6193 Open Cluster 4.3 Ara 5.2
C83 NGC 4945   NGC 4945 Galaxy 17,000 Centaurus 9
C84 NGC 5286   NGC 5286 Globular Cluster 36 Centaurus 7.6
C85 IC 2391 Omicron Velorum Cluster Open Cluster 0.5 Vela 2.5
C86 NGC 6397   P0321a Globular Cluster 7.5 Ara 5.7
C87 NGC 1261   Ngc1261eso Globular Cluster 55.5 Horologium 8.4
C88 NGC 5823   NGC 5823 in Cir Open Cluster 3.4 Circinus 7.9
C89 NGC 6087[note 1] S Norma Cluster NGC 6087 Open Cluster 3.3 Norma 5.4
C90 NGC 2867   NGC 2867HST Planetary Nebula 5.5 Carina 10
C91 NGC 3532 Wishing Well Cluster NGC 3532 in Carina Open Cluster 1.6 Carina 3
C92 NGC 3372 Eta Carinae Nebula Carina Nebula Nebula 7.5 Carina 3
C93 NGC 6752   NGC 6752 Hubble WikiSky Globular Cluster 13 Pavo 5.4
C94 NGC 4755 Jewel Box A Snapshot of the Jewel Box cluster with the ESO VLT Open Cluster 4.9 Crux 4.2
C95 NGC 6025   NGC 6025 Open Cluster 2.5 Triangulum Australe 5.1
C96 NGC 2516 NGC 2516 in Carina Open Cluster 1.3 Carina 3.8
C97 NGC 3766 Pearl Cluster NGC 3766 in Cen Open Cluster 5.8 Centaurus 5.3
C98 NGC 4609   NGC 4609 Open Cluster 4.2 Crux 6.9
C99 - Coalsack Nebula Coal.sack.nebula.arp.300pix Dark Nebula 0.61 Crux -
C100 IC 2944 Lambda Centauri Nebula Bok globules in IC2944 Open Cluster and Nebula 6 Centaurus 4.5
C101 NGC 6744   Ngc 6744 Galaxy 34,000 Pavo 9
C102 IC 2602 Theta Car Cluster IC 2602 Open Cluster 0.492 Carina 1.9
C103 NGC 2070 Tarantula Nebula Spitzer-TarantulaNebula Open Cluster and Nebula 170 Dorado 8.2
C104 NGC 362   GALEX image of NGC 362 Globular Cluster 27.7 Tucana 6.6
C105 NGC 4833   NGC 4833 Hubble WikiSky Globular Cluster 19.6 Musca 7.4
C106 NGC 104 47 Tucanae 47tuc Globular Cluster 14.7 Tucana 4
C107 NGC 6101   NGC 6101 Globular Cluster 49.9 Apus 9.3
C108 NGC 4372   NGC 4372 in Musca Globular Cluster 18.9 Musca 7.8
C109 NGC 3195   Ngc3195 Planetary Nebula 5.4 Chamaeleon 11.6
Caldwell number NGC number Common name Picture Object type Distance to object in thousands of light years Constellation Apparent magnitude
  1. ^ C89 was mistakenly written as NGC 6067 in the original, but its description is that of NGC 6087.

See also


  1. ^ a b c d e f g O'Meara, Stephen James (2002). The Caldwell Objects. Cambridge University Press. ISBN 978-0-521-82796-6.
  2. ^ "Caldwell Club Introduction". Retrieved 2006-09-08.
  3. ^ a b Moore, Patrick (December 1995). "Beyond Messier: The Caldwell Catalogue". Sky & Telescope: 38. Archived from the original (subscription required) on 2009-01-16. Retrieved 2006-08-29.
  4. ^ Mobberley, Martin (2009). The Caldwell Objects and How to Observe Them. Springer. ISBN 978-1-4419-0325-9.
  5. ^ Jones, Kenneth Glyn (1991). "Introduction". Messier's Nebulae & Star Clusters. Cambridge University Press. pp. 1–8. ISBN 0-521-37079-5.

External links

Astronomical catalog

An astronomical catalog or catalogue is a list or tabulation of astronomical objects, typically grouped together because they share a common type, morphology, origin, means of detection, or method of discovery. Astronomical catalogs are usually the result of an astronomical survey of some kind.


C56 or C-56 may refer to :

C-56 Lodestar, an American military aircraft

C-56 (Michigan county highway)

JNR Class C56, a class of Japanese steam locomotive

Caldwell 56 (NGC 246, the Skull Nebula), a planetary nebula in the constellation Cetus

Sickness Insurance (Sea) Convention, 1936 code

Two Knights Defense ECO code

Planetary nebula referenced as C56 in Caldwell catalogue

Ovarian cancer ICD-10 code

Hexachlorocyclopentadiene, an organochlorine compound that is a precursor to several pesticidesRelated:

S56 (disambiguation) (example: the S56, a Soviet submarine labeled C-56 using Cyrillic alphabet)


C58 or C-58 may refer to :

C-58 Bolo, an American military aircraft

C-58 (Michigan county highway)

JNR Class C58, a class of Japanese steam locomotive

HMS Fiji (C58), a 1940 British Royal Navy cruiser

Caldwell 58 (NGC 2360), an open cluster in the constellation Canis Majorand also :

Two Knights Defense ECO code

NGC 2360 referenced C58 in Caldwell catalogue

Minimum Age (Sea) Convention (Revised), 1936 code

a Toyota C transmission

Choriocarcinoma ICD-10 code


C89 may refer to:

C89 (C version) or ANSI C, a C programming-language version

Ruy Lopez (ECO code: C60–C99), a chess opening

KNHC, a radio station in Seattle, Washington known as C89.5

Night Work (Women) Convention (Revised), 1948, an ILO convention

NGC 6087 (Caldwell catalogue: C89), an open clusters in the constellation Norma

Sylvania Airport, an airport in Wisconsin with the FAA LID "C89"

Charles Messier

Charles Messier (French: [me.sje]; 26 June 1730 – 12 April 1817) was a French astronomer most notable for publishing an astronomical catalogue consisting of 110 nebulae and star clusters, which came to be known as the Messier objects. The purpose of the catalogue was to help astronomical observers, in particular comet hunters like himself, distinguish between permanent and transient visually diffuse objects in the sky.

Coalsack Nebula

The Coalsack Nebula (Southern Coalsack, or simply the Coalsack) is the most prominent dark nebula in the skies, being easily visible to the naked eye as a dark patch silhouetted against the southern Milky Way. It is located at a distance of approximately 600 light-years away from Earth, in the constellation Crux.

Double Cluster

The Double Cluster (also known as Caldwell 14) is the common name for the open clusters NGC 869 and NGC 884 (often designated h Persei and χ Persei, respectively), which are close together in the constellation Perseus. Both visible with the naked eye, NGC 869 and NGC 884 lie at a distance of 7500 light years. NGC 869 has a mass of 3700 solar masses and NGC 884 weighs in at 2800 solar masses; however, later research has shown both clusters are surrounded with a very extensive halo of stars, with a total mass for the complex of at least 20,000 solar masses. Based on their individual stars, the clusters are relatively young, both 12.8 million years old. In comparison, the Pleiades have an estimated age ranging from 75 million years to 150 million years. There are more than 300 blue-white super-giant stars in each of the clusters. The clusters are also blueshifted, with NGC 869 approaching Earth at a speed of 39 km/s (24 mi/s) and NGC 884 approaching at a similar speed of 38 km/s (24 mi/s). Their hottest main sequence stars are of spectral type B0.

Herschel 400 Catalogue

The Herschel 400 catalogue is a subset of William Herschel's original Catalogue of Nebulae and Clusters of Stars, selected by Brenda F. Guzman (Branchett), Lydel Guzman, Paul Jones, James Morrison, Peggy Taylor and Sara Saey of the Ancient City Astronomy Club in St. Augustine, Florida, United States c. 1980. They decided to generate the list after reading a letter published in Sky & Telescope by James Mullaney of Pittsburgh, Pennsylvania, USA.In this letter Mr. Mullaney suggested that William Herschel's original catalogue of 2,500 objects would be an excellent basis for deep sky object selection for amateur astronomers looking for a challenge after completing the Messier Catalogue.

The Herschel 400 is a subset of John Herschel's General Catalogue of Nebulae and Clusters published in 1864 of 5,000 objects, and hence also of the New General Catalogue.

The catalogue forms the basis of the Astronomical League's Herschel 400 club. In 1997, another subset of 400 Herschel objects was selected by the Rose City Astronomers of Portland, Oregon as the Herschel II list, which forms the basis of the Astronomical League's Herschel II Program.

Messier object

The Messier objects are a set of 110 astronomical objects catalogued by the French astronomer Charles Messier in his "Catalogue des Nébuleuses et des Amas d'Étoiles" ("Catalogue of Nebulae and Star Clusters").

Because Messier was interested in finding only comets, he created a list of non-comet objects that frustrated his hunt for them. The compilation of this list, in collaboration with his assistant Pierre Méchain, is known as the Messier catalogue. This catalogue of objects is one of the most famous lists of astronomical objects, and many Messier objects are still referenced by their Messier number.

The catalogue includes some astronomical objects that can be observed from Earth’s Northern Hemisphere such as deep-sky objects, a characteristic which makes the Messier objects extremely popular targets for amateur astronomers.A preliminary version first appeared in Memoirs of the French Academy of Sciences in 1771,

and the last item was added in 1966 by Kenneth Glyn Jones, based on Messier's observations.

The first version of Messier's catalogue contained 45 objects and was published in 1774 in the journal of the French Academy of Sciences in Paris. In addition to his own discoveries, this version included objects previously observed by other astronomers, with only 17 of the 45 objects being Messier’s.

By 1780 the catalogue had increased to 80 objects. The final version of the catalogue containing 103 objects was published in 1781 in the Connaissance des Temps for the year 1784.

However, due to what was thought for a long time to be the incorrect addition of Messier 102, the total number remained 102. Other astronomers, using side notes in Messier's texts, eventually filled out the list up to 110 objects.The catalogue consists of a diverse range of astronomical objects, ranging from star clusters, nebula to galaxies. For example, Messier 1 is a supernova remnant, known as the Crab Nebula, and the great spiral Andromeda Galaxy is M31. Many further inclusions followed in the next century when the first addition came from Nicolas Camille Flammarion in 1921, who added Messier 104 after finding Messier’s side note in his 1781 edition exemplar of the catalogue. M105 to M107 were added by Helen Sawyer Hogg in 1947, M108 and M109 by Owen Gingerich in 1960, and M110 by Kenneth Glyn Jones in 1967.

NGC 4889

NGC 4889 (also known as Coma B) is an E4 supergiant elliptical galaxy. It was discovered in 1785 by the British astronomer Frederick William Herschel I, who catalogued it as a bright, nebulous patch. The brightest galaxy within the northern Coma Cluster, it is located at a median distance of 94 million parsecs (308 million light years) from Earth. At the core of the galaxy is a supermassive black hole that heats the intracluster medium through the action of friction from infalling gases and dust. The gamma ray bursts from the galaxy extend out to several million light years of the cluster.

As with other similar elliptical galaxies, only a fraction of the mass of NGC 4889 is in the form of stars. They have a flattened, unequal distribution that bulges within its edge. Between the stars is a dense interstellar medium full of heavy elements emitted by evolved stars. The diffuse stellar halo extends out to one million light years in diameter. Orbiting the galaxy is a very large population of globular clusters. NGC 4889 is also a strong source of soft X-ray, ultraviolet, and radio frequency radiation.

As the largest and the most massive galaxy easily visible to Earth, NGC 4889 has played an important role in both amateur and professional astronomy, and has become a prototype in studying the dynamical evolution of other supergiant elliptical galaxies in the more distant universe.

NGC 884

NGC 884 (also known as χ Persei) is an open cluster located 7600 light years away in the constellation of Perseus. It is the easternmost of the Double Cluster with NGC 869. NGC 869 and 884 are often designated h and χ Persei, respectively. The cluster is most likely around 12.5 million years old. Located in the Perseus OB1 association, both clusters are located physically close to one another, only a few hundred light years apart. The clusters were first recorded by Hipparchus, but have likely been known since antiquity.

The Double Cluster is a favorite of amateur astronomers. These bright clusters are often photographed or observed with small telescopes. Easy to find, the clusters are visible with the unaided eye between the constellations of Perseus and Cassiopeia as a brighter patch in the winter Milky Way. The Double Cluster was also included in the Caldwell catalogue, a catalogue of astronomical objects for amateur observation.In small telescopes the cluster appears as a beautiful assemblage of bright stars located in a rich star field. Dominated by bright blue stars the cluster also hosts a few orange stars that add to the visual interest. Both clusters together offer a spectacular low magnification view.


A nebula (Latin for "cloud" or "fog"; pl. nebulae, nebulæ, or nebulas) is an interstellar cloud of dust, hydrogen, helium and other ionized gases. Originally, the term was used to describe any diffuse astronomical object, including galaxies beyond the Milky Way. The Andromeda Galaxy, for instance, was once referred to as the Andromeda Nebula (and spiral galaxies in general as "spiral nebulae") before the true nature of galaxies was confirmed in the early 20th century by Vesto Slipher, Edwin Hubble and others.

Most nebulae are of vast size; some are hundreds of light years in diameter. A nebula that is barely visible to the human eye from Earth would appear larger, but no brighter, from close by. The Orion Nebula, the brightest nebula in the sky and occupying an area twice the diameter of the full Moon, can be viewed with the naked eye but was missed by early astronomers. Although denser than the space surrounding them, most nebulae are far less dense than any vacuum created on Earth – a nebular cloud the size of the Earth would have a total mass of only a few kilograms. Many nebulae are visible due to fluorescence caused by embedded hot stars, while others are so diffuse they can only be detected with long exposures and special filters. Some nebulae are variably illuminated by T Tauri variable stars.

Nebulae are often star-forming regions, such as in the "Pillars of Creation" in the Eagle Nebula. In these regions the formations of gas, dust, and other materials "clump" together to form denser regions, which attract further matter, and eventually will become dense enough to form stars. The remaining material is then believed to form planets and other planetary system objects.

Owl Nebula

The Owl Nebula (also known as Messier 97, M97 or NGC 3587) is a planetary nebula located approximately 2,030 light years away in the constellation Ursa Major. It was discovered by French astronomer Pierre Méchain on February 16, 1781. When William Parsons, 3rd Earl of Rosse, observed the nebula in 1848, his hand-drawn illustration resembled an owl's head. It has been known as the Owl Nebula ever since.The nebula is approximately 8,000 years old. It is approximately circular in cross-section with a little visible internal structure. It was formed from the outflow of material from the stellar wind of the central star as it evolved along the asymptotic giant branch. The nebula is arranged in three concentric shells, with the outermost shell being about 20–30% larger than the inner shell. The owl-like appearance of the nebula is the result of an inner shell that is not circularly symmetric, but instead forms a barrel-like structure aligned at an angle of 45° to the line of sight.The nebula holds about 0.13 solar masses of matter, including hydrogen, helium, nitrogen, oxygen, and sulfur; all with a density of less than 100 particles per cubic centimeter. Its outer radius is around 0.91 ly (0.28 pc) and it is expanding with velocities in the range of 27–39 km/s into the surrounding interstellar medium.The 14th magnitude central star has since reached the turning point of its evolution where it condenses to form a white dwarf. It has 55–60% of the Sun's mass, 41–148 times the brightness of the Sun, and an effective temperature of 123,000 K. The star has been successfully resolved by the Spitzer Space Telescope as a point source that does not show the infrared excess characteristic of a circumstellar disk.

Patrick Moore

Sir Patrick Alfred Caldwell-Moore, (4 March 1923 – 9 December 2012) was an English amateur astronomer who attained prominent status in that field as a writer, researcher, radio commentator and television presenter.Moore was President of the British Astronomical Association, co-founder and president of the Society for Popular Astronomy, author of over seventy books on astronomy, and presenter of the world's longest-running television series with the same original presenter, BBC's The Sky at Night. He became known as a specialist in Moon observation and for creating the Caldwell catalogue. Idiosyncrasies such as his rapid diction and monocle made him a popular and instantly recognisable figure on British television.

Moore was also a self-taught xylophonist, glockenspiel player and pianist, as well as an accomplished composer. He was an amateur cricketer, golfer and chess player. In addition to many popular science books, he wrote numerous works of fiction. He was an opponent of fox hunting, an outspoken critic of the European Union, supporter of the UK Independence Party and served as chairman of the short-lived anti-immigration United Country Party. He served in the Royal Air Force during World War II; Moore claimed that his fiancée was killed during the war, and he never married or had children.

RCW Catalogue

The RCW Catalogue (from Rodgers, Campbell & Whiteoak) is an astronomical catalogue of Hα-emission regions in the southern Milky Way, described in (Rodgers et al. 1960). It contains 182 objects, including many of the earlier Gum catalogue (84 items) objects.

The later Caldwell catalogue included some objects from the RCW catalogue. There is also some overlap with the Sharpless catalogue-2 (312 items), although that primarily covered the northern hemisphere, whereas RCW and Gum primarily covered the southern hemisphere.

The RCW catalogue was compiled by Alexander William Rodgers, Colin T. Campbell and John Bartlett Whiteoak. They catalogued southern nebulae while working under Bart Bok at the Mount Stromlo Observatory in Australia in the 1960s.


Sh2-155 (also designated Sharpless 155 or S155) is a diffuse nebula in the constellation Cepheus, within a larger nebula complex containing emission, reflection, and dark nebulosity. It is widely known as the Cave Nebula, though that name was applied earlier to Ced 201, a different nebula in Cepheus. Sh2-155 is an ionized H II region with ongoing star formation activity, at an estimated distance of 725 parsecs (2400 light-years) from Earth.Sh2-155 was first noted as a galactic emission nebula in 1959 in the extended second edition of the Sharpless catalogue, being a part of the much larger Cep OB3 Association. Although Sh2-155 is relatively faint for amateur observation, some of its structure may be seen visually through a moderately sized telescope under dark skies.Sh2-155 lies at the edge of the Cepheus B cloud (part of the Cepheus molecular cloud), and is ionized by young stars from the Cep OB3 association. It has been suggested that radiation from the hot O-type star HD 217086 is compressing the region, triggering the formation of a new generation of stars. A study of the region's young stellar objects by the Chandra X-ray Observatory and Spitzer Space Telescope shows a progression of stellar ages in front of the cloud, supporting the hypothesis of triggered star-formation.

Sharpless catalog

The Sharpless catalog is a list of 313 HII regions (emission nebulae), intended to be comprehensive north of declination −27°. (It does include some nebulae south of that declination as well.) The first edition was published in 1953 with 142 objects (Sh1), and the second and final version was published by US astronomer Stewart Sharpless in 1959 with 312 objects. Sharpless also includes some planetary nebulae and supernova remnants, in addition to HII regions.In 1953 Stewart Sharpless joined the staff of the United States Naval Observatory Flagstaff Station, where he surveyed and cataloged H II regions of the Milky Way using the images from the Palomar Sky Survey. From this work Sharpless published his catalog of H II regions in two editions, the first in 1953 with 142 nebula. The second and final edition was published in 1959 with 312 nebulae.Sharpless coordinates are based on the star catalogs Bonner Durchmusterung (BD) and Cordoba Durchmusterung (CD), but the second release was adjusted to the 1900 epoch.In the second release, some coordinates for southern hemisphere regions have an uncertainty over 1 minute of arc. This can make them difficult to find, so a revised catalog called BFS (Blitz, Fich and Stark) was released. BFS has 65 new regions and about 20 removals. Most of the removed items were taken out because they were the aforementioned nebula or remnants.The 312 items in Sharpless sometimes overlap with the 110 Messier objects (M), 7,840 objects in the New General Catalogue (NGC), the Caldwell catalogue (that itself is a "best of" from other catalogues, with 109 items), and the RCW catalog. Contemporary catalogs were Gum and RCW, but they mainly covered the southern hemisphere.

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