Constellations
Webpages concerning "Constellations"
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Wikipedia-Article "Constellations"
- For other uses, see Constellation (disambiguation).
A constellation is a group of stars visibly related to each other in a particular configuration.
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Explanation
In three-dimensional space, most of the stars we see have little relation to one another, but can appear to be grouped on the celestial sphere of the night sky. Humans excel at finding patterns and throughout history have grouped stars that appear close to one another into constellations.
An "unofficial" constellation, that is, one that may be widely known but is not recognized by the International Astronomical Union, is called an asterism. An example is the grouping called the Big Dipper (US) or the Plough (UK).
The stars in a constellation or asterism rarely have any astrophysical relationship to each other; they just happen to appear close together in the sky as viewed from Earth and typically lie many light years apart in space. However, one exception to this is the Ursa Major moving group.
The grouping of stars into constellations is essentially arbitrary, and different cultures have had different constellations, although a few of the more obvious ones tend to recur frequently, e.g., Orion and Scorpius.
The International Astronomical Union (IAU) divides the sky into 88 official constellations with precise boundaries, so that every direction belongs to exactly one constellation. In the northern celestial hemisphere, these are mostly based upon the constellations of the ancient Greek tradition, passed down through the Middle Ages, and contains the signs of the zodiac.
The constellation boundaries were drawn up by Eugène Delporte in 1930, and he drew them along vertical and horizontal lines of right ascension and declination. However, he did so for the epoch B1875.0, which means that due to precession of the equinoxes, the borders on a modern star map (eg, for epoch J2000) are already somewhat skewed and no longer perfectly vertical or horizontal. This skew will increase over the years and centuries to come.
History of the Constellations
- Main article: List of Constellations
Our current list is based on those listed by the Roman astronomer, Claudius Ptolemy, who lived in Alexandria, Egypt. (Claudius Ptolemy, the astronomer, was not related to the Greek kings of Egypt named Ptolemy.)
In more recent times this list has been added to, to fill gaps between Ptolemy's patterns. The Greeks considered the sky as including both constellations and dim spaces between. But Renaisance star catalogs by Johann Bayer and John Flamsteed required every star to be in a constellation, and the number of visible stars in a constellation to be manageably small.
Twelve of the constellations in the southern celestial hemisphere were not observable by the Greeks, and were created by Dutch navigators Pieter Dirkszoon Keyser and Frederick de Houtman in the sixteenth century and first cataloged by Johann Bayer.
Other proposed constellations didn't make the cut, most notably Quadrans Muralis (now part of Boötes) for which the Quadrantid meteors are named. Also the ancient constellation Argo Navis was so big that it was broken up into several different constellations, for the convenience of stellar cartographers.
Constellations in variant cultures
- Main article: Chinese constellation
Chinese constellations are different from the western constellations, due to the independent development of ancient Chinese astronomy. Ancient Chinese skywatchers divided their night sky in a different way, but there are also similarities. The Chinese counterpart of the 12 western zodiac constellations are the 28 "Xiu" (宿) or "mansions" (a literal translation).
Star names
All modern constellation names are Latin proper names or words, and some stars are named using the genitive of the constellation in which they are found. The genitive is formed using the usual rules of Latin grammar, and for those unfamiliar with that language the form of the genitive is unpredictable and must be memorized. Some examples include: Aries → Arietis; Taurus → Tauri; Gemini → Geminorum; Virgo → Virginis; Libra → Librae; Pisces → Piscium; Lepus → Leporis.
These names include Bayer designations such as Alpha Centauri, Flamsteed designations such as 61 Cygni, and variable star designations such as RR Lyrae. However, many fainter stars will just be given a catalog number designation (in each of various star catalogs) that does not incorporate the constellation name.
For more information about star names, see Star designations and the list of stars by constellation.
See also
| The 88 modern Constellations |
| Andromeda | Antlia | Apus | Aquarius | Aquila | Ara | Aries | Auriga | Boötes | Caelum | Camelopardalis | Cancer | Canes Venatici | Canis Major | Canis Minor | Capricornus | Carina | Cassiopeia | Centaurus | Cepheus | Cetus | Chamaeleon | Circinus | Columba | Coma Berenices | Corona Australis | Corona Borealis | Corvus | Crater | Crux | Cygnus | Delphinus | Dorado | Draco | Equuleus | Eridanus | Fornax | Gemini | Grus | Hercules | Horologium | Hydra | Hydrus | Indus | Lacerta | Leo | Leo Minor | Lepus | Libra | Lupus | Lynx | Lyra | Mensa | Microscopium | Monoceros | Musca | Norma | Octans | Ophiuchus | Orion | Pavo | Pegasus | Perseus | Phoenix | Pictor | Pisces | Piscis Austrinus | Puppis | Pyxis | Reticulum | Sagitta | Sagittarius | Scorpius | Sculptor | Scutum | Serpens | Sextans | Taurus | Telescopium | Triangulum | Triangulum Australe | Tucana | Ursa Major | Ursa Minor | Vela | Virgo | Volans | Vulpecula |
External links
- The Constellations
- Photographic Atlas of the Constellations
- Celestia free 3D realtime space-simulation (OpenGL)
- Stellarium realtime sky rendering program (OpenGL)
- Strasbourg Astronomical Data Center Files on official IAU constellation boundaries (the older NASA ADC service does not function anymore)
- Interactive Sky Charts (Allows navigation through the entire sky with variable star detail, optional constellation lines)
- http://www.astronomical.org/constellations/obs.html
- http://www.seds.org/Maps/Stars_en/Fig/const.html
- Constellations Articles
- Full constellation diagrams resembling their names
- Images of constellations