CALDWELL CATALOGUE (CONTINUED)
RA (2000.0) Dec.
C NGC/IC Constellation Type h min ° Magnitude Size () Comment
56 246 Cetus planetary nebula 00 47.0 11 53 8.6 4 3
57 6822 Sagittarius irregular galaxy 19 44.9 14 48 8.8 20 10
58 2360 Canis Major open cluster 07 17.8 15 37 7.2 13
59 3242 Hydra planetary nebula 10 24.8 18 38 7.8 0.27 GHOST OF JUPITER
60 4038 Corvus Sc galaxy 12 01.9 18 52 10.5 2.6 2 ANTENNAE
61 4039 Corvus Sp galaxy 12 01.9 18 53 10.5 2.6 2 ANTENNAE
62 247 Cetus SAB galaxy 00 47.1 20 46 9.1 20 7
63 7293 Aquarius planetary nebula 22 29.6 20 48 7.3 13 HELIX NEBULA
64 2362 Canis Major open cluster 07 18.8 24 57 4.1 8
65 253 Sculptor Scp galaxy 00 47.6 25 17 7.1 25 7 Silver Coin Galaxy
66 5694 Hydra globular cluster 14 39.6 26 32 10.2 3.6
67 1097 Fornax SBb galaxy 02 46.3 30 16 9.2 9 7
68 6729 Corona Australis bright nebula 19 01.9 36 58 — 1.0
69 6302 Scorpius planetary nebula 17 13.7 37 06 9.6 2 1
70 300 Sculptor Sd galaxy 00 54.9 37 41 8.1 20 15
71 2477 Puppis open cluster 07 52.3 38 33 5.8 27
72 55 Sculptor SB galaxy 00 15.1 39 13 7.9 25 4
73 1851 Columba globular cluster 05 14.1 40 03 7.3 11
74 3132 Vela planetary nebula 10 07.7 40 26 8.2 1.4 0.9
75 6124 Scorpius open cluster 16 25.6 40 40 5.8 29
76 6231 Scorpius open cluster 16 54.0 41 48 2.6 15
77 5128 Centaurus radio galaxy 13 25.5 43 01 6.8 18 14 CENTAURUS A
78 6541 Corona Australis globular cluster 18 08.0 43 42 6.6 13
79 3201 Vela globular cluster 10 17.6 46 25 6.7 18
80 5139 Centaurus globular cluster 13 26.8 47 29 3.6 36 Centauri
81 6352 Ara globular cluster 17 25.5 48 25 8.1 7
82 6193 Ara open cluster 16 41.3 48 46 5.2 15
83 4945 Centaurus SBc galaxy 13 05.4 49 28 8.7 20 4
84 5286 Centaurus globular cluster 13 46.4 51 22 7.6 9
85 IC 2391 Vela open cluster 08 40.2 53 04 2.5 50
86 6397 Ara globular cluster 17 40.7 53 40 5.7 26
87 1261 Horologium globular cluster 03 12.3 55 13 8.4 7
88 5823 Circinus open cluster 15 05.7 55 36 7.9 10
89 6087 Norma open cluster 16 18.9 57 54 5.4 12
90 2867 Carina planetary nebula 09 21.4 58 19 9.7 12
91 3532 Carina open cluster 11 06.4 58 40 3.0 55
92 3372 Carina bright nebula 10 45.0 59 50 — 120 120 Carinae Nebula
93 6752 Pavo globular cluster 19 10.9 59 59 5.4 20
94 4755 Crux open cluster 12 53.6 60 20 4.2 10 KAPPA CRUCIS CLUSTER
95 6025 Triangulum Australis open cluster 16 03.7 60 30 5.1 12
96 2516 Carina open cluster 07 58.3 60 52 3.8 30
97 3766 Centaurus open cluster 11 36.1 61 37 5.3 12
98 4609 Crux open cluster 12 42.3 62 58 6.9 5
99 — Crux dark nebula 12 53 63 — 420 300 COALSACK
100 IC 2944 Centaurus cluster 11 36.6 63 02 4.5 60 40
101 6744 Pavo SBb galaxy 19 09.8 63 51 8.3 16 10
102 IC 2602 Carina open cluster 10 43.2 64 24 1.9 50
103 2070 Dorado bright nebula 05 38.7 69 06 — 30 20 TARANTULA NEBULA
104 362 Tucana globular cluster 01 03.2 70 51 6.6 13
105 4833 Musca globular cluster 12 59.6 70 53 7.3 14
106 104 Tucana globular cluster 00 24.1 72 05 4.0 31 FORTY-SEVEN TUCANAE
107 6101 Apus globular cluster 16 25.8 72 12 9.3 11
108 4372 Musca globular cluster 12 25.8 72 40 7.8 19
109 3195 Chamaeleon planetary nebula 10 09.5 80 52 8.4 40 30
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Callisto Outermost and darkest of the GALILEAN SATEL
-LITESof JUPITER. It has an albedo of only 0.2. Callisto is heavily cratered and is the only member of the group to show no clear surface signs of current or past geological activity. Callisto’s density of 1.9 g/cm3suggests that it is composed of rock and ice in a 40:60 mixture. Gravity measurements made by the Galileo orbiter during close flybys of Callisto suggest that its interior is only weakly dif-ferentiated (seeDIFFERENTIATION), and that the rock is not all concentrated into a core, in contrast to Callisto’s neigh-bour GANYMEDE. Perplexingly, measurements made by the Galileo orbiter hinted at a magnetic field, apparently generated at a shallow depth within Callisto as a result of its orbital passage through Jupiter’s MAGNETOSPHERE. One way to explain this would be if Callisto has a salty ocean no more than 100 km (60 mi) below its icy surface, but this is hard to reconcile with the great age of the surface implied by the density of CRATERS.
Although Callisto’s craters are clearly produced by meteoroidal or cometary impact, they are rather different from those found on the Moon. For example, Callisto has very few craters less than about 60 km (40 mi) in diame-ter, showing that the satellite was bombarded by a differ-ent population of impactors from that responsible for lunar craters. The largest craters have a subdued shape, as if Callisto’s LITHOSPHEREhas not been strong enough to support their topography. There are also a few enormous impact basins marked by concentric rings of fractures; the largest of these, named VALHALLA, is about 4000 km (2500 mi) across. About a dozen linear chains of craters have been identified on Callisto, each of which was proba-bly produced by the serial impact of fragments of a comet broken up by tidal forces during a close passage of Jupiter (seeSHOEMAKER–LEVY9). See data at JUPITER
Caloris Planitia (‘Basin of Heat’) Largest single feature on MERCURYimaged by MARINER10. It is situated near one
of the planet’s hot poles and centred on 30º.5N 189º.8W.
The Caloris Planitia is an enormous multi-ring impact structure 1300 km (800 mi) in diameter – a quarter that of the planet. Imaged half-lit from the departing spacecraft, it is defined by a ring of discontinuous mountains, the Montes Caloris, roughly 2 km (1.2 mi) high. The BASIN
floor consists of smooth plains with quasi-concentric and other ridges, transected by younger crack-like GRABEN. The ejecta blanket extends to a distance of approximately 700 km (430 mi) beyond the Montes Caloris; it comprises tracts of uneven hummocky plains and lineated terrain.
The whole structure is undoubtedly the modified scar left by the impact of an asteroid-sized body, the floor being the end result of refilling of the crater by the crusting-over, semi-molten ASTHENOSPHERE. On the other side of Mer-cury, antipodal to Caloris, is a region of ‘weird terrain’, an extraordinary place of hills and valleys that break into other landforms; it probably formed as a result of shock-waves from the impact that created Caloris.
Caltech Submillimeter Observatory (CSO) Enclosed 10.4-m (34-ft) radio dish with a hexagonally segmented mirror, at MAUNA KEA OBSERVATORY, Hawaii. The tele-scope is operated by the CALIFORNIA INSTITUTE OF TECH
-NOLOGY under contract from the National Science Foundation, and has been in regular use since 1988. The instrument operates at wavelengths between 350m and 1.3 mm, and can be linked with the nearby JAMES CLERK MAXWELL TELESCOPEfor short-baseline interferometry.
Calypso Small satellite of SATURN, discovered in 1980 by Dan Pascu (1938– ) and others in images from the
VOYAGERmissions. It is irregular in shape, measuring about 30 16 16 km (19 10 10 mi). With a distance from the centre of the planet of 294,700 km (183,100 mi), it is co-orbital with TETHYS and TELESTO. Calypso and Telesto have circular, near-equatorial orbits, near the L5 and L4LAGRANGIAN POINTS, respectively, of Tethys’ orbit around Saturn, with a period of about 1.89 days.
Callisto
C
CallistoAsgard, a multi-ring impact basin on Callisto, imaged by the Galileo spacecraft. Callisto’s icy surface is heavily scarred by impact cratering.
Caloris PlanitiaThis vast (1300 km/800 mi diameter) multi-ring impact basin on Mercury was imaged during the Mariner 10 mission in 1974.
Shockwaves from the impact, early in Mercury’s history, have produced unusual geological features on the opposite hemisphere of the planet.
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Cancer Cambridge Low Frequency Synthesis Telescope
(CLFST) East–west aperture synthesis radio telescope consisting of 60 trackable Yagi antennae, operated by the
MULLARD RADIO ASTRONOMY OBSERVATORYand situated close to the RYLE TELESCOPE. The individual antennae are located on a 4.6-km (2.9-mi) baseline, and have a working frequency of 151 MHz
Cambridge Optical Aperture Synthesis Telescope (COAST) Instrument built by the MULLARD RADIO ASTRONOMY OBSERVATORY to extend the interferometric image-reconstruction techniques used in radio astronomy to optical and near-infrared wavelengths. It consists of an array of five 400-mm (16-in.) telescopes, of which up to four are in use at any one time. They can be used to synthe-size a virtual telescope mirror 100 m (330 ft) in diameter, yielding images showing detail as fine as 0.001 (1 milliarc-second). COAST produced its first images in 1995.
Cambridge Radio Observatory SeeMULLARD RADIO ASTRONOMY OBSERVATORY
Camelopardalis See feature article
Camilla MAIN-BELT ASTEROID; number 107. It is notable because it is accompanied by a small moon.
Campbell, (William) Wallace (1862–1938) American astronomer and mathematician who measured a large num-ber of radial velocities. As director of Lick Observatory (1900–1930), he founded the observatory’s southern-hemisphere station in Chile and designed important acces-sory instruments for Lick’s telescopes, including the Mills spectrographs. Campbell led an eclipse expedition in 1922, which confirmed Einstein’s general theory of relativity by showing that the Sun’s mass was sufficient to deflect light waves from other stars. With Heber CURTIS, he undertook a huge photographic survey of stellar spectra to determine the radial velocities of stars. This project had two important results: it allowed Campbell to map the local Milky Way and our Sun’s motion relative to other nearby stars, and it led to the discovery of over a thousand spectroscopic binaries.
Canada–France–Hawaii telescope Optical/infrared telescope of 3.6-m (142-in.) aperture located at MAUNA KEA OBSERVATORY and operated jointly by the National Research Council of Canada, the Centre National de la Recherche Scientifique of France and the University of Hawaii. The instrument began operation in 1979, and its suite of instruments includes high-resolution wide-field imagers.
canals, Martian Elusive network of dark linear markings on the surface of Mars, reported by some observers from around 1870 until well into the 20th century. In 1877 Giovanni SCHIAPARELLImarked a number of very narrow features on his map of Mars which he referred to as canali, which in Italian means ‘channels’ or ‘canals’. But when his findings were translated into English, it was the latter sense, with its implication of artificial construction, that found its way into reports. Controversy continued in the 1880s, some astronomers claiming they could see the
‘canals’, while others could not. In the 1890s, their exis-tence was championed by Percival LOWELL, who founded Lowell Observatory in Flagstaff, Arizona, largely to study them. He became convinced that they were waterways constructed by intelligent beings to irrigate a desiccating planet. Only when close-up images were returned by the Mariner craft and later Mars probes was the existence of canals disproved with certainty.
Martian ‘canals’ make an intriguing episode in the annals of observational astronomy. No canal was ever convincingly photographed, yet highly detailed maps were prepared from sketches made at the eyepiece that showed canals in prodigious numbers. Their explanation is part psychological, part physiological. There is no denying the integrity of some who reported having observed canals,
but equally there is no doubting that other observers were over-zealous in seeking evidence to fit a theory. The phys-iological factor was explained by Eugène ANTONIADIand others. When the eye is straining to discern detail at the very limits of visibility – and the disk of Mars is small, even at favourable oppositions – the brain can misinter-pret what the eye beholds. In particular, in conditions of low contrast, it ‘joins the dots’ to form lines between dis-crete features, and conjures firm borders between areas of differing brightness.
Cancer See feature article
C
CANCER (GEN. CANCRI, ABBR. CNC)
F
aintest constellation of the zodiac, lying between Gemini and Leo.Mythologically, it represents the crab that was crushed underfoot by Hercules during his fight with the Hydra. The brightest star is Cnc, a K4 giant of mag.
3.52, distance 290 l.y. Cnc is a long-period binary divisible through small telescopes, mags. 5.0 and 6.2. Even easier to divide is Cnc, mags. 4.0 and 6.6.
The constellation’s most celebrated feature is M44, also known as PRAESEPEor the Manger, a large open star cluster. North and south of it lie and Cnc, known as the ASELLI(‘asses’). In the south of the constellation, next to Cnc, binoculars show M67, a smaller and fainter open cluster 2500 l.y. away.
CAMELOPARDALIS (GEN. CAMELOPARDALIS, ABBR. CAM)
F
airly large but faint northern constellation, representing a giraffe; it extends from the northern borders of Perseus and Auriga towards the north celestial pole. Camelopardalis was introduced by Petrus Plancius in 1613, supposedly to commemorate the Biblical animal that carried Rebecca to Isaac. Its brightest star,Cam, is a wide double, mags. 4.0 and 8.6. NGC 1502 is a small open cluster from which a chain of stars called Kemble’s Cascade runs for 2 º towards neighbouring Cassiopeia.
CANES VENATICI (GEN. CANUM VENATICORUM, ABBR. CVN)
N
orthern constellation positioned beneath the tail of Ursa Major, representing a pair of hunting dogs, Asterion and Chara, held on a leash by neighbouring Boötes. Canes Venatici was introduced by Johannes Hevelius in 1687. CVn, known as COR CAROLI, is an easy double, mags. 2.9 and 5.6. Y CVn is a red supergiant semiregular variable known as La Superba, with range 5.0–6.5 and period roughly 160 days. The constellation’s most famous feature is the spiral galaxy M51, known as the WHIRLPOOL GALAXY. Other spirals visible with small instruments are M63 and M94. One of the best globular clusters in northern skies is M3, just on the naked-eye limit at 6th magnitude.CANIS MAJOR (GEN. CANIS MAJORIS, ABBR. CMA)
P
rominent constellation just south of the celestial equator, containing the brightest star in the sky, SIRIUS. Canis Major represents the larger of the two dogs of Orion and is one of the constellations recognized since the time of the ancient Greeks. (ADHARA) and CMa are difficult double stars with much fainter companions. UW CMa is an eclipsing binary, range 4.8–5.3, period 4.4 days. M41 is a naked-eye open cluster 4º south of Sirius, similar in apparent size to the full moon and containing some 80 stars of 7th magnitude and fainter.NGC 2362 is a small open cluster surrounding the mag. 4.4 blue supergiant CMa, its brightest member. See alsoMIRZAM; WEZEN
BRIGHTEST STARS
Name RA dec. Visual Absolute Spectral Distance
h m ° mag. mag. type (l.y.)
Sirius 6 45 16 43 1.44 1.45 A0m 8.6
Adhara 6 59 28 58 1.50 4.10 B2 431
Wezen 7 08 26 24 1.83 6.87 F8 1800
Mirzam 6 23 17 57 1.98 3.95 B1 499
Aludra 7 24 29 18 2.45 7.51 B5 3200
Furud 6 20 30 03 3.02 2.05 B2.5 336
2 7 03 23 50 3.02 6.46 B3 2600
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Candy, Michael Philip (1928–94) English-born astronomer who worked at Royal Greenwich Observatory (1947–69) and Perth Observatory (1969–93). From Perth, he directed an observational programme that con-tributed greatly to the study of Halley’s Comet at its 1986/87 apparition. Candy was an expert on the orbits of comets and asteroids, and has one of each type of object named after him.
Canes Venatici See feature article, page 69 Canis Major See feature article, page 69 Canis Minor See feature article
cannibalism Merging of a GALAXYinto a much larger and more massive one, so that its content is incorporated without a major change in the structure of the larger galaxy. This process is thought to explain how CD GALAX
-IESat the centres of clusters have become so bright and massive. Cannibalism of dwarf satellites also seems to have played a role in the growth of the halos of SPIRAL GALAXIES, exemplified by the distinct streams of stars in the Milky Way and the ANDROMEDA GALAXY, which may be the assimilated remnants of former companions.
Cannon, Annie Jump (1863–1941) American astronomer who, working at the Harvard College
Obser-vatory under the direction of Edward C. PICKERING, refined the system for classifying stellar spectra. In 1896, after teaching physics at Wellesley College, Cannon joined Harvard’s staff of ‘Pickering’s women’, a group of com-puting assistants hired mainly to work on the HENRY DRAP
-ER CATALOGUEof stellar spectra.
Taking the alphabetical spectral classification begun by Williamina FLEMING and Antonia C. MAURY, Cannon dropped several categories and rearranged the sequence to give O, B, A, F, G, K, M, from the hottest stars to the coolest. White or blue stars were classified as type O, B or A, yellow stars as F or G, orange stars were designated K, and red stars as M. This scheme, which is the basis for the present-day HARVARD SYSTEM of spectral classification, was used by Cannon in the first ever catalogue of stellar spectra, for the 1122 brightest stars (1901). Later, she added types R, N and S, plus ten subcategories based upon finer spectral features.
In the course of her work, Cannon visually examined and classified hundreds of thousands of spectra: the Henry Draper Catalogue, filling nine volumes of the Harvard Annals, ultimately contained almost 400,000 stars sorted by spectral class. Cannon also discovered five novae, 300 new variable stars and published extensive catalogues of these objects in 1903 and 1907. She was the first woman to be elected an officer of the American Astronomical Society, but because of a reluctance of the scientific com-munity to accept women in astronomy, she did not receive a regular appointment at Harvard until 1938, just two years before she retired.
Canopus The star Carinae, the second-brightest star in the entire sky, visual mag. 0.62, distance 313 l.y. It is a white supergiant of spectral type F0 Ib, more than 10,000 times as luminous as the Sun. The Hipparcos satellite detected variations of about 0.1 mag., but the period (if any) and cause of the variation are not known.
Canopus is named after the helmsman of the Greek King Menelaus.
Cape Canaveral SeeKENNEDY SPACE CENTER
Capella The star Aurigae, at visual mag. 0.08 the sixth-brightest star in the sky, distance 42 l.y. It is a spectroscopic binary, consisting of two yellow giants with an orbital period of 104 days. Various spectral types have been given for this pair, but they are likely to be near G6 III and G2 III. The star’s name comes from the Latin meaning ‘she-goat’.
Cape Observatory See ROYAL OBSERVATORY, CAPE OF GOOD HOPE
Cape Photographic Durchmusterung (CPD) Cata-logue compiled from the first large photographic survey of the southern sky, made at the Cape Observatory between 1885 and 1900 under the direction of David
GILL. Data for the CPD were taken from Gill’s photo-graphic plates by Jacobus KAPTEYN. It contains 455,000 stars to 10th magnitude from dec. 18º to 90º and, achieved before the CÓRDOBA DURCHMUSTERUNG, com-plements the BONNER DURCHMUSTERUNG. It was later revised by Robert INNES.
Capricornus See feature article
captured rotation SeeSYNCHRONOUS ROTATION
Carafe Galaxy (Cannon’s Carafe Galaxy) SEYFERT
GALAXYin the southern constellation of Caelum (RA 04h 28m.0 dec. 47º24), part of a group with NGC 1595 and NGC 1598. Long-exposure images show a curved jet of emerging material, possibly the result of gravitational interaction with NGC 1595.
carbon Sixth element, chemical symbol C; it is fourth in order of COSMIC ABUNDANCE. Its properties include:
Candy, Michael Philip
C
CANIS MINOR (GEN. CANIS MINORIS, ABBR. CMI)
C
onstellation on the celestial equator, representing the smaller of the two dogs following Orion, the other being Canis Major. Its leading star is PROCYON, the eighth-brightest in the sky. Apart from Procyon and CMi, known as Gomeisa, there is little of note.BRIGHTEST STARS
Name RA dec. Visual Absolute Spectral Distance
h m ° mag. mag. type (l.y.)
Procyon 7 39 5 14 0.40 2.68 F5 11.4
Gomeisa 7 27 8 18 2.89 0.70 B8 170
cannibalismA Hubble Space Telescope image of the elliptical galaxy NGC 1316 in Fornax. The dark dust clouds and bluish star clusters are probably remnants of a collision 100 million years ago, during which NGC 1316 consumed a smaller galaxy.
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carbon star
atomic number 6; atomic mass of the naturally occurring element 12.01115; melting point c.3820 K (it sublimes at 3640 K); boiling point 5100 K; valence 2, 3 or 4. Carbon has seven ISOTOPES, with atomic masses from 10 to 16, two of which are stable (carbon-12 and carbon-13). Car-bon-12 is used to define the ATOMIC MASS UNIT, and so its atomic mass is exactly 12. The naturally occurring ele-ment contains carbon-12 (98.89%) and carbon-13 (1.11%) plus variable but small amounts of carbon-14. In its free state, carbon exists as amorphous carbon, graphite and diamond.
Carbon is unique in the vast number and variety of compounds that it can form. The study of its reactions forms the entire discipline of organic chemistry. Carbon’s property of forming hexagonal rings and long-chain mol-ecules and of linking with hydrogen, nitrogen and oxygen makes it the basis of life. In the form of carbon dioxide (CO2) and methane (CH4) it produces the two most sig-nificant GREENHOUSEgases.
Carbon-14 is radioactive, with a half-life of 5730 years, and forms the basis for carbon-dating archaeologi-cal remains. It is continually produced in the Earth’s atmosphere from nitrogen-14 by COSMIC RAYS. Once produced, it is incorporated into living material. After the death of the organism, the decay of the carbon-14 slowly reduces its abundance relative to carbon-12, and so allows determination of the age.
Carbon plays an important role in the CARBON–NITRO
-GEN–OXYGEN CYCLE, which is the major helium-produc-ing nuclear reaction in massive stars. It is unusually abundant in some types of peculiar star (seeASTROCHEM
-ISTRY), and may comprise the bulk of the material form-ing some white dwarfs.
carbonaceous chondrite Chondritic METEORITEwith atomic magnesium to silicon ratio greater than 1.02. Car-bonaceous chondrites are subdivided, on chemical or tex-tural grounds, into seven groups, each (apart from the CH group) named after its type specimen. The CI (for Ivuna) group has six members, including TAGISH LAKE. These meteorites have a composition very close to that of
carbonaceous chondrite Chondritic METEORITEwith atomic magnesium to silicon ratio greater than 1.02. Car-bonaceous chondrites are subdivided, on chemical or tex-tural grounds, into seven groups, each (apart from the CH group) named after its type specimen. The CI (for Ivuna) group has six members, including TAGISH LAKE. These meteorites have a composition very close to that of