constellation

constellation, in common usage, group of stars that appear to form a configuration in the sky; properly speaking, a constellation is a definite region of the sky in which the configuration of stars is contained. Identifiable groupings of bright stars have been recognized and named since ancient times, the names corresponding to mythological figures (e.g., Perseus, Andromeda, Hercules, Orion), animals (e.g., Leo the Lion, Cygnus the Swan, Draco the Dragon), or objects (e.g., Libra the Balance, Corona the Crown). Ptolemy listed 48 constellations in his Almagest (2d cent. A.D.).

As systematic observations were extended to the entire southern sky from the 17th cent. on, more constellations were added to the list by J. Bayer, N. L. de Lacaille, and others. For example, Ptolemy's 48th constellation, Argo Navis, representing a ship, was divided into four smaller constellations corresponding to different parts of the ship. The final list consists of 88 constellations, each associated with a definite region of the sky. Thus, the entire celestial sphere is divided according to a plan prepared by Eugene Delporte, with the boundaries fixed by international agreement in 1930, along lines of right ascension and declination (see equatorial coordinate system). The 12 constellations located along or near the ecliptic, the apparent path of the sun through the heavens, are known as the constellations of the zodiac; the remaining constellations are officially classified as northern (28 constellations) or southern (48 constellations).

The table entitled Constellations lists the constellations according to their official Latin names, with the English equivalents and the approximate positions given. In some cases, the English name for a constellation is not an exact translation of the Latin; e.g., the English name for Pictor reflects the fact that the figure in the constellation is not the painter himself but his easel. Certain familiar star groups, or asterisms, are not listed as constellations because they form only part of a larger constellation; the Big Dipper and Little Dipper are parts of the constellations Ursa Major and Ursa Minor, and the Northern Cross is part of Cygnus.

Bright stars within a constellation are designated according to a system originated by Bayer in 1603: the brightest star is designated by the Greek letter alpha followed by the genitive form of the Latin name for the constellation, the second brightest star by beta, and so on, with Roman letters and pairs of Roman letters being used after the Greek letters have all been assigned. For example, the brightest star in Taurus, Aldebaran, is designated Alpha Tauri, the second brightest, Elnath, is designated Beta Tauri, and so on. The alphabetical order does not always indicate the stars' relative brightness: in a few cases, e.g., Ursa Major, the assignment of a Bayer name is according to position rather than brightness.

Any of certain groupings of stars that were imagined by those who named them to form images of objects, mythological figures, or creatures in the sky. They are useful in helping sky gazers and navigators locate certain stars. A constellation's stars are often designated by its name and letters of the Greek alphabet in order of brightness. Of 88 named constellations in Western astronomy, about half retain the names Ptolemy gave the 48 he identified in his Almagest. Seealso zodiac.

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Aries (, symbol , Unicode ♈) is one of the constellations of the zodiac. It lies between Pisces to the west and Taurus to the east.

Notable features

Aries' stars are rather faint except for α Ari (Hamal) and β Ari (Sharatan). Other important stars are γ Ari (Mesarthim) and δ Ari (Botein).

Teegarden's star, a recent discovery in the constellation, is one of Sun's closest neighbors around 12 light years away. It exhibits one of the largest proper motions known at about 5.06 arc seconds/yr.

Notable deep sky objects

The few deep sky objects in Aries are very dim. They include the galaxies NGC 697 (northwest of β Ari), NGC 772 (southeast of β Ari), NGC 972 (in the constellation's northern corner), and NGC 1156 (northwest of δ Ari).

Graphic visualization

The stars of the constellation Aries can be connected in an alternative way, which graphically shows the ram running (or jumping).

The ram's head consists of the stars α Ari, λ Ari, and β Ari: α Ari being of the second magnitude and beta Arietis of the third magnitude.

The ram's body consists of the stars α Ari, η Ari, ε Ari, 41 Ari, and 35 Ari: ε Ari and 41 Ari being of the fourth magnitude.

The ram's tail consists of the stars 35 Ari, 41 Ari, and 39 Ari.

The star γ Ari, of fourth magnitude, represents the ram's front foot, and the star δ Ari, also of fourth magnitude, represents the ram's hind foot.

Mythology

According to Greek mythology, Aries was a ram, possibly a golden one, that got the gods' mission to save Helle and Phrixos from a king Cretheus for false accusations. The ram managed to save Phrixos into the land of Colchis, while Helle instead ended up in the arms of Poseidon. In gratitude for this, Phrixos sacrificed the ram to the gods and hanged its skin in a temple.

Astrology and religion

The Western astrological sign Aries of the tropical zodiac (March 21–April 20) differs from the astronomical constellation and the Hindu astrological sign of the sidereal zodiac (August 15 - October 15).

References

• H. A. Rey, The Stars—A New Way To See Them. Enlarged World-Wide Edition. Houghton Mifflin, Boston, 1997. ISBN 0-395-24830-2.
• Ian Ridpath and Wil Tirion (2007). Stars and Planets Guide, Collins, London. ISBN 978-0007251209. Princeton University Press, Princeton. ISBN 978-0691135564.

External links

• The Deep Photographic Guide to the Constellations: Aries
• NightSkyInfo.com: Constellation Aries
• Star Tales – Aries