Stellar Sky

Stellar Sky

 

the aggregate of heavenly bodies visible at night in the sky. With good conditions it is possible to see with the unaided eye at one time in the night half of the sky about 2,500 stars (to the sixth magnitude), the majority of which are situated near the band of the Milky Way. Use of a telescope permits the observation of a significantly greater number of stars (see Table 1).

Table 1. Number of stars in the stellar sky
Stellar magnitude (apparent)Number of stars to the given magnitude
113
240
3100
4500
51,600
64,800
715,000
842,000
9125,000
10350,000
11900,000
122,300,000
135,700,000
1414,000,000
1532,000,000
1671,000,000
17150,000,000
18300,000,000
19550,000,000
201,000,000,000
212,000,000,000

For ease of orientation, the stellar sky is divided into parts, called constellations. In each constellation the brightest stars form characteristic groups, which, after training, can be easily recognized in the sky. The division of stars into primary constellations, including zodiacal ones, dates from early antiquity. The names of the constellations are derived partly from Greek mythology (for example, Andromeda, Perseus, Delphinus) or are connected with various occupations of the ancients—agriculture, stock breeding, hunting (for example, Virgo, Bootes, Pisces, Lepus). Constellations that were distinguished much later received names connected with travel and the development of technology (for example, Sextans, Microscopium). In all, 88 constellations are recognized (see Table 2), the boundaries between which were established in 1930 according to a resolution of the International Astronomical Union. Table 2 gives the names of the constellations as well as their abbreviations. The bright stars in constellations are designated by letters of the Greek alphabet or by numbers. Certain types of stars have special designations; variables, for example, are denoted by capital Latin letters. A number of stars have proper names (see Table 3). Most stars, however, are designated by the name of a star catalog with information on the given star and the number under which the star is recorded in it (for example, Lacaille 9352).

One can also observe in the stellar sky star clusters, stellar associations, galactic nebulas, galaxies, quasars, clusters of galaxies, and other objects; bodies constituting the solar system

Table 2. Constellations
NameAbbreviationPosition in sky
AndromedaAndN
Antlia (Pump)AntS
Apus (Bird of Paradise)ApsS
Aquarius (Water-pourer)AqrEq
Aquila (Eagle)AqlEq
Ara (Sacred Altar)AraS
Aries (Ram)AriN
Auriga (Charioteer)AurN
Bootes (Ox-driver)BooN
Caelum (Chisel)CaeS
Camelopardalis (Giraffe)CamN
Cancer (Crab)CncN
Canes Venatici (Hunting Dogs)CVnN
Canis Major (Greater Dog)CMaS
Canis Minor (Smaller Dog)CMiN
Capricorn (Horned Goat)CapS
Carina (Keel)CarS
CassiopeiaCasN
Centaurus (Centaur)CenS
CepheusCepN
Cetus (Sea Monster)GetEq
ChamaelonChaS
Circinus (Pair of Compasses)CirS
Columba (Dove)ColS
Coma Berenices (Berenice’s Hair)ComN
Corona Australis (Southern Crown)CrAS
Corona Borealis (Northern Crown)CrBN
Corvus (Raven)CrvS
Crater (Cup)CrtS
Crux (Cross)CruS
Cygnus (Swan)CygN
Delphinus (Dolphin)DelN
Dorado (Gilded Fish)DorS
Draco (Dragon)DraN
Equuleus (Foal)EquN
Eridanus (River)EriS
Fornax (Furnace)ForS
Gemini (Twins)GemN
Grus (Crane)GruS
HerculesHerN
Horologium (Clock)HorS
Hydra (Water Monster)HyaS
Hydrus (Water Snake)HyiS
Indus (Indian)IndS
Lacerta (Lizard)LacN
Leo (Lion)LeoN
Leo Minor (Little Lion)LMiN
Lepus (Hare)LepS
Libra (Balance)LibS
Lupus (Wolf)LupS
LynxLynN
Lyra (Lyre)LyrN
Mensa (Table Mountain)MenS
Microscopium (Microscope)MicS
Monoceros (Unicorn)MonEq
Musca (Fly)MusS
Norma (Square)NorS
Octans (Octant)OctS
Ophiuchus (Serpent-holder)OphEq
OrionOriEq
Pavo (Peacock)PavS
Pegasus (Flying Horse)PegN
PerseusPerN
PhoenixPheS
Pictor (Painter)PicS
Pisces (Fish)PscEq
Piscis Austrinus (Southern Fish)PsAS
Puppis (Stern)PupS
Pyxis (Compass)PyxS
Reticulum (Net)RetS
Sagitta (Arrow)SgeN
Sagittarius (Archer)SgrS
Scorpio (Scorpion)ScoS
SculptorSclS
Scutum (Shield)SetEq
Serpens (Serpent)SerEq
Sextans (Sextant)SexEq
Taurus (Bull)TauN
Telescopium (Telescope)TelS
Triangulum (Triangle)TriN
Triangulum Australe (Southern Triangle)TrAS
Tucana (Toucan)TucS
Ursa Major (Greater Bear)UMaN
Ursa Minor (Smaller Bear)UMiN
Vela (Sails)VelS
Virgo (Maiden or Virgin)VirEq
Volans (Flying Fish)VolS
Vulpecula (Little Fox)VulN

such as planets, asteroids, and comets; and artificial space objects, such as artificial earth satellites and space probes.

Most of these objects can be observed only with the aid of a telescope. Among those visible to the naked eye are the open clusters of the Pleiades and the Hyades in the constellation Taurus; Praesepe in the constellation Cancer; globular clusters in the constellations Tucana and Centaurus; galactic nebulas in the constellation Orion; galaxies in the constellation Andromeda; the Large and Small Magellanic Clouds; the planets Venus, Jupiter, Mars, Saturn, Mercury, and Uranus; the asteroid Vesta; comets; and the brightest artificial earth satellites.

Table 3. Names of Stars
Alamachγ Andromedae
Alaraphβ Virginis
Albireoβ Cygni
Achernarα Eridani
Alcorg Ursae Majoris
Alcyoneη Tauri
Aldebaranα Tauri
Alderaminα Cephei
Algenibγ Pegasi
Algiebaγ Leonis
Algolβ Persei
Alhenaγ Geminorum
Aliothε Ursae Majoris
Alphardα Hydrae
Alpheratzα Andromedae
Alramiα Sagittarii
Altairα Aquilae
Antaresα Scorpii
Arcturusα Bootis
Bellatrixγ Orionis
Benetnashη Ursae Majoris
Betelgeuseα Orionis
Canopusα Carinae
Capellaα Aurigae
Capriβ Cassiopeiae
Castorα Geminorum
Celaeno16 Tauri
Denebα Cygni
Deneb Kaitosβ Ceti
Denebolaβ Leonis
Dubheα Ursae Majoris
Electra17 Tauri
Fomalhautα Piscis A’ustrinus
Gemmaα Coronae Borealis
Hamalα Arietis
Kochabβ Ursae Minoris
Markabα Pegasi
Megrezδ UrsaeMajoris
Menkarα Ceti
Merakβ Ursae Majoris
Merope23 Tauri
Mirau Ceti
Mirachβ Andromedae
Mirfakα Persei
Mirzamβ Canis Majoris
Mizarε Ursae Majoris
Nathβ Tauri
Phactα Columbae
Phecdaγ Ursae Majoris
Pleione28 Tauri
Polarisα Ursae Minoris
Polluxβ Geminorum
Procyonα Canis Minoris
Ras Algethiα Herculis
Ras Alhagueα Ophiuchi
Regulusα Leonis
Rigelβ Orionis
Sadalmelikα Aquarii
Siriusα Canis Majoris
Spicaα Virginis
Thubanα Draconis
Vegaα Lyrae

The background of the sky is never completely black, since the sky gleams weakly because of atomic processes in the upper layers of the atmosphere. This night-sky glow from 1 square degree produces an illumination equivalent on the average to that from a star of magnitude 4.5. By day almost all celestial bodies disappear in the bright blue background of the air that is illuminated by the sun. Besides the sun, only the moon and Venus are visible to the unaided eye in the clear daytime sky.

The appearance of the stellar sky changes continuously because of the apparent diurnal rotation of the celestial sphere, which is explained by the earth’s rotation, and changes slowly because of the annual apparent movement of the sun among the stars, which occurs as a result of the earth’s revolution around the sun.

References in periodicals archive ?