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BY GEORGE: Constellations Defined

Most of the well-known constellations date back to ancient Greece or earlier, but the precise list remained somewhat fuzzy until the early 20th century. Then, in a series of resolutions from 1922 to 1930, the International Astronomical Union (IAU) divided the celestial sphere into 88 precisely defined constellations with official spellings and abbreviations.

Every constellation name has two forms: the nominative, for use when you're talking about the constellation itself, and the genitive, or possessive, which is used in star names. For instance, Hamal, the brightest star in the constellation Aries (nominative form), is also called Alpha Arietis (genitive form), meaning literally "the Alpha of Aries."  I hope that’s as technical as I’ll get.  A lot of this is new to me as well.

Constellations are human inventions, and different cultures have divided and organized the stars in different ways, though a few patterns are nearly universal. The constellations recognized by scientists today are the ones that arose out of the European tradition.

The major European constellations are very old. A few, notably the Great Bear, are widely believed to predate the invention of writing some 5,000 years ago. And there's evidence that many, including the zodiacal constellations, originated in Mesopotamia sometime before 1,000 BC. Somehow, the Mesopotamian constellations were imported into ancient Greece, but there's no record of how or why this occurred.

The Greeks seem to have invented some constellations of their own, notably the Perseus family, around the same time that they adopted the Mesopotomian constellations, and a few more were added after 350 BC. The comprehensive list of ancient constellations appeared in a book written around AD 150 by the Greco-Egyptian astronomer Claudius Ptolemy. This book, which summarized all of classical astronomy, is now known by its Arabic name: Almagest, meaning "the Greatest."

Astronomy was neglected in Europe for more than a millennium following the Almagest, but it revived in the 15th century, when European navigators started to explore unknown waters. When these sailors ventured south of the equator, they saw stars that were not in Ptolemy's catalog and organized them into new constellations. Later, in the telescopic era, astronomers invented additional constellations to fill the gaps between the traditional ones.

Rome conquered the entire Greek-speaking world by 30 BC, and the Greek constellation names were translated into Latin, the primary language of the Roman Empire. Latin has remained the standard language for scientific nomenclature ever since. That's why all constellations invented since classical times have Latin names, as do all species of plants and animals.

Most constellation names are simple common nouns with obvious English equivalents. For instance, Leo is Latin for "the lion" or "a lion." The Greeks sometimes tried to associate the constellation Leo with some particular lion from their mythology, but there's every reason to believe that when they inherited this constellation from Mesopotamia, it was just a generic lion.

Other constellations are named after specific people or things. For instance, Eridanus is one particular mythological river, not the Latin equivalent of "a river" or "the river." The constellation Perseus is often nicknamed the Hero in English, but this is a little misleading, as that nickname could apply equally well to Hercules.

Not surprisingly, there are plenty of intermediate cases. Thus, Cetus means just a sea monster, whale, or large fish, but it's very likely that the constellation's inventor was thinking of the particular monster that tried to eat Andromeda. And Gemini is the common Latin word for "twins" but also the special epithet of the mythological twins Castor and Pollux.  And you thought the English language was confusing.


By: George Elliott


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