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constellations

Because the human brain has a powerful urge to recognize pattern, we see patterns in the night sky, patterns like the Big Dipper. These patterns are called “asterisms.” Most asterisms are due to our point of view, and are not the result of a real, physical grouping of stars. An asterism may include small nearby stars and giant but distant ones.

Names of the constellations

Many cultures have had named constellations: the Chinese, for example. But because modern astronomy arose out of the Western tradition, the names now used internationally have Western roots. A number of constellations are mentioned in Homer (9th century bce), and Greek references are frequent by the 6th century bce, but the names appear to have come from even older cultures along the Euphrates River, possibly by way of the Phoenicians.

Drawing on the work of the astronomer Eudoxus, sometime around 270bce a poet named Aratus wrote a long poem called Phenomena, in which he described 44 constellations and told their stories. This work was extremely popular in classical times. No less an author than Cicero translated it into Latin. To this day, most books that tell the stories of the constellations are retellings of Aratus.

Ptolemy listed 48 constellations and their locations in his He Mathematike Syntaxis (2nd century ad). Medieval Europeans knew this work as the Almagest, its translation into Arabic. Most of the constellation names given in the Almagest are still in use.

Astronomers' view of constellations

To the astronomer, a constellation is not an asterism, but a well-defined area on the celestial sphere. So, for example, every constellation that is a part of the zodiac must occupy exactly one-twelfth of the celestial equator, a point recognized by the ancient Greeks. Every point on the celestial sphere must lie in one constellation or another; the entire celestial sphere is tiled with constellations.

As European astronomers began to travel to the Southern Hemisphere, more names were required to cover the part of the celestial sphere that can never be seen from Earth's Northern Hemisphere. The names of twelve of these southern constellations, suggested by Pieter Dirckszoon Keyzer, Amerigo Vespucci, Andrea Corsali and Pedro de Medina, were canonized by their use in 1630 in plate 49 of Johnn Bayer's extremely popular star atlas, Uranometria. By the end of the 17th century, astronomers were inventing new constellations to fill those regions which, because they contained few prominent stars, had never been identified with a particular constellation.

Differing definitions of the constellations and the use of curved boundaries (which made it a bit more difficult to determine in which constellation a given location lay) led the International Astronomical Union to standardize the names and the boundaries of the constellations in 1930, making them all run either north-south or east-west, like lines of latitude and longitude on the Earth.²

The names of the constellations are used in naming prominent stars. In a star's name the genitive form of the constellation's name is used, or it is abbreviated. The redrawing of the constellations' boundaries in 1930 resulted in a few stars no longer being in the constellations from which they take their names.

The system of three letter abbreviations for the names of constellations was proposed by Hertzsprung and Russell, and adopted with slight modifications by the First General Assembly of the IAU in 1922.¹ At the same meeting, it was decided that astronomers would use only the Latin form of the names of constellations.

The genitive form and abbreviation are given in the table below. The size is given in square degrees.² In comments, the letter refers to the first record of the name:

• P = mentioned in Ptolemy, Almagest (2nd century ce);
• B = Johann Bayer, Uranometria (1603)
• H = Johann Hewelke (1611–1687, Latin, Johannes Hevelius) of Danzig in his posthumously published celestial atlases, Firmamentum sobiescanium and Prodromus Astronomiae (1690).
• L = Nicholas Louis de Lacaille, Caelum Australe Stelliferum (1763)

1. A. Fowler, ed.
First General Assembly, held at Rome, May 2nd to May 10th, 1922.
Transactions of the International Astronomical Union. Volume 1.
London: Imperial College Bookstall, no date [1922 ?].

Pages 23, 158, 207.  See also Transactions of the IAU, volume 4, page 221; volume 9, pages 66 and 77.

2. E. Delaporte.
Delimitation scientifique des constellations (tables et cartes).
Cambridge (UK): Cambridge University Press, 1930.

See also:
A. Levin.
Areas of the constellations.
British Astronomical Association Handbook (1935)

3. Aratus, in Callimachus, Hymns and Fragments; Lycophron; Aratus.
G. R. Mair, translator.
Loeb Classical Library.
London: William Heinemann; New York: G. P. Putnams, 1921.

Douglas Kidd.
Aratus. Phaenomena.
Cambridge: Cambridge University Press, 1997.

Very expensive scholarly book.

Aaron Poochigian, trans.
Aratus: Phaenomena.
Baltimore: Johns Hopkins University Press, 2010.

for further reading

www.iau.org/public/themes/constellations/

Michael E. Bakich.
Cambridge Guide to the Constellations.
Cambridge University Press, 1995.

Wonderful.

Theony Condos.
Star Myths of the Greeks and Romans: A Sourcebook Containing the Constellations of Pseudo-Eratosthenes and the Poetic Astronomy of Hyginus.
Phanes Press, 1997.

Sources in the Western tradition, for scholars.

Jacqueline Mitton.
Once Upon a Starry Night.
National Geographic Society, 2004.
or, by the same author,
Zoo in the Sky.
National Geographic Society, 1998.

H. A. Rey
Find the Constellations.
Houghton Mifflin, 1954. Several revised editions, most recent edition in 1988.

Classic children's book, by the author of the Curious George books. It has stood the test of time and is just as useful to adults wishing to learn the constellations.

Julius D. W. Staal.
The New Patterns in the Sky. Myths and Legends of the Stars.
McDonald and Woodward, 1996. (Revision of a 1988 edition)

Recommended as an introduction at middle school and above.

Copyright © 2000 Sizes, Inc.  All rights reserved.
Last revised: 26 January 2004.