The 88 Constellations
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13-OY2e_APP(351-364).qxd 14/02/05 10:24 PM Page 351 APPENDIX A The 88 Constellations Latin name English name First-magnitude star(s) Andromeda Andromeda Antlia The Air-Pump Apus The Bee Aquarius The Water-Bearer Aquila The Eagle Altair Ara The Altar Aries The Ram Auriga The Charioteer Capella Boötes The Herdsman Arcturus Cælum The Sculptor’s Tools Camelopardalis The Giraffe Cancer The Crab Canes Venatici The Hunting Dogs Canis Major The Great Dog Sirius Canis Minor The Little Dog Procyon Capricornus The Sea-Goat Carina The Keel Canopus Cassiopeia Cassiopeia Centaurus The Centaur Alpha Centauri, Cepheus Cepheus Agena Cetus The Whale Chamæleon The Chameleon Circinus The Compasses Columba The Dove Coma Berenices Berenice’s Hair Corona Australis The Southern Crown Corona Borealis The Northern Crown Corvus The Crow Crater The Cup Crux Australis The Southern Cross Acrux, Beta Crucis 351 13-OY2e_APP(351-364).qxd 14/02/05 10:24 PM Page 352 352 The 88 Constellations Latin name English name First-magnitude star(s) Cygnus The Swan Deneb Delphinus The Dolphin Dorado The Swordfish Draco The Dragon Equuleus The Little Horse Eridanus The River Achernar Fornax The Furnace Gemini The Twins Pollux Grus The Crane Hercules Hercules Horologium The Clock Hydra The Watersnake Hydrus The Little Snake Indus The Indian Laceta The Lizard Leo The Lion Regulus Leo Minor The Little Lion Lepus The Hare Libra The Balance Lupus The Wolf Lynx The Lynx Lyra The Lyre Vega Mensa The Table Microscopium The Microscope Monoceros The Unicorn Musca Australis The Southern Fly Norma The Rule Octans The Octant Ophiuchus The Serpent-Bearer Orion The Hunter Rigel, Betelgeux Pavo The Peacock Pegasus The Flying Horse Perseus Perseus Phœnix The Phœnix Pictor The Painter Pisces The Fishes Piscis Australis The Southern Fish Fomalhaut Puppis The Poop Pyxis The Compass Reticulum The Net Sagitta The Arrow Sagittarius The Archer Scorpius The Scorpion Sculptor The Sculptor Scutum The Shield Serpens The Serpent Sextans The Sextant Taurus The Bull Aldebaran Telescopium The Telescope Triangulum The Triangle Triangulum Australe The Southern Triangle Tucana The Toucan Ursa Major The Great Bear Ursa Minor The Little Bear Vela The Sails Virgo The Virgin Spica Volans The Flying Fish Vulpecula The Fox 13-OY2e_APP(351-364).qxd 14/02/05 10:24 PM Page 353 APPENDIX B Glossary Absolute magnitude. The apparent magnitude that a star would have if it could be observed from a standard dis- tance of 10 parsecs (32.6 light-years). Achromatic object-glass. An object-glass which has been cor- rected so as to eliminate chromatic aberration or false colour as much as possible. Albedo. The reflecting power of a planet or other non- luminous body. The Moon is a poor reflector; its albedo is a mere 7% on average. Altazimuth mounting for a telescope. A mounting on which the telescope may swing freely in any direction. Altitude. The angular distance of a celestial body above the horizon. Ångström unit. One hundred-millionth part of a centimetre. Aphelion. The furthest distance of a planet or other body from the Sun in its orbit. Apogee. The furthest point of the Moon from the Earth in its orbit. Apparent magnitude. The apparent brightness of a celestial body. The lower the magnitude, the brighter the object: thus the sun is approximately –27, the Pole Star +2, and the faintest stars detectable by modern techniques around +30. Asteroids. One of the names for the minor planet swarm. Astrolabe. An ancient instrument used to measure the alti- tudes of celestial bodies. Astronomical unit. The mean distance between the Earth and the Sun. It is equal to 149 598 500 km. 353 13-OY2e_APP(351-364).qxd 14/02/05 10:24 PM Page 354 354 Glossary Aurora. Auroræ are ‘polar lights’; Aurora Borealis (northern) and Aurora Australis (southern). They occur in the Earth’s upper atmosphere, and are caused by charged particles emitted by the Sun. Baily’s beads. Brilliant points seen along the edge of the Moon just before and just after a total solar eclipse. They are caused by the sunlight shining through valleys at the Moon’s limb. Barycentre. The centre of gravity of the Earth-Moon system. Because the Earth is 81 times as massive as the Moon, the barycentre lies well inside the Earth’s globe. Binary star. A stellar system made up of two stars, genuinely associated, and moving round their common centre of gravity. The revolution periods range from millions of years for very widely-separated visual pairs down to less than half an hour for pairs in which the components are almost in contact with each other. With very close pairs, the components cannot be seen separately, but may be detected by spectroscopic methods. Black hole. A region round a very small, very massive col- lapsed star from which not even light can escape. BL Lacertæ objects. Variable objects which are powerful emitters of infra-red radiation, and are very luminous and remote. They are of the same nature as quasars. Cassegrain reflector. A reflecting telescope in which the sec- ondary mirror is convex; the light is passed back through a hole in the main mirror. Its main advantage is that it is more compact than the Newtonian reflector. Celestial sphere. An imaginary sphere surrounding the Earth, whose centre is the same as that of the Earth’s globe. Cepheid. A short-period variable star, very regular in behav- iour; the name comes from the prototype star, Delta Cephei. Cepheids are astronomically important because there is a definite law linking their variation periods with their real luminosities, so that their distances may be obtained by sheer observation. Chromosphere. That part of the Sun’s atmosphere which lies above the bright surface or photosphere. Circumpolar star. A star which never sets. For instance, Ursa Major (the Great Bear) is circumpolar as seen from England; Crux Australis (the Southern Cross) is circumpo- lar as seen from New Zealand. Conjunction. (1) A planet is said to be in conjunction with a star, or with another planet, when the two bodies are apparently close together in the sky. (2) For the inferior planets, Mercury and Venus, inferior conjunction occurs when the planet is approximately between the Earth and the Sun; superior conjunction, when the planet is on the far side of the Sun and the three bodies are again lined up. Planets beyond the Earth’s orbit can never come to inferior conjunction, for obvious reasons. Corona. The outermost part of the sun’s atmosphere, made up of very tenuous gas. It is visible with the naked eye only during a total solar eclipse. 13-OY2e_APP(351-364).qxd 14/02/05 10:24 PM Page 355 Glossary 355 Cosmic rays. High-velocity particles reaching the Earth from outer space. The heavier cosmic-ray particles are broken up when they enter the upper atmosphere. Cosmology. The study of the universe considered as a whole. Counterglow. The English name for the sky-glow more gen- erally called by its German name of the Gegenschein. Culmination. The maximum altitude of a celestial body above the horizon. Declination. The angular distance of a celestial body north or south of the celestial equator. It corresponds to latitude on the Earth. Dichotomy. The exact half-phase of the Moon or an inferior planet. Doppler effect. The apparent change in wavelength of the light from a luminous body which is in motion relative to the observer. With an approaching object, the wavelength is apparently shortened, and the spectral lines are shifted to the blue end of the spectral band; with a receding body there is a red shift, since the wavelength is apparently lengthened. Double star. A star made up of two components – either gen- uinely associated (binary systems) or merely lined up by chance (optical pairs). Driving clock. A mechanism for driving a telescope round at a rate which compensates for the axial rotation of the Earth, so that the object under observation remains fixed in the field of view. Dwarf novæ. A term sometimes applied to the U Geminorum (or SS Cygni) variable stars. Earthshine. The faint luminosity on the night side of the Moon, frequently seen when the Moon is in its crescent phase. It is due to light reflected on to the Moon from the Earth. Eclipse, lunar. The passage of the Moon through the shadow cast by the Earth. Lunar eclipses may be either total or partial. At some eclipses, totality may last for approxi- 3 mately 14 hours, though most are shorter. Eclipse, solar. The blotting-out of the Sun by the Moon, so that the Moon is then directly between the Earth and the Sun. Total eclipses can last for over 7 minutes under excep- tionally favourable circumstances. In a partial eclipse, the Sun is incompletely covered. In an annular eclipse, exact alignment occurs when the Moon is in the far part of its orbit, and so appears smaller than the Sun; a ring of sun- light is left showing round the dark body of the Moon. Strictly speaking, a solar ‘eclipse’ is the occultation of the Sun by the Moon. Eclipsing variable (or Eclipsing Binary). A binary star in which one component is regularly occulted by the other, so that the total light which we receive from the system is reduced. The prototype eclipsing variable is Algol (Beta Persei). Ecliptic. The apparent yearly path of the Sun among the stars. It is more accurately defined as the projection of the Earth’s orbit on to the celestial sphere. 13-OY2e_APP(351-364).qxd 14/02/05 10:24 PM Page 356 356 Glossary Elongation.