Constellation
A constellation is a recognized grouping of stars that forms a pattern in the night sky, often named for its resemblance to mythological figures, animals, or objects. Most modern constellations have their roots in ancient cultures, particularly the Greeks, who inherited knowledge from earlier civilizations such as the Sumerians and Babylonians. There are officially eighty-eight constellations, each assigned a specific area of the sky, and they depict a wide array of figures, including heroes and creatures from mythology. The origins of these patterns date back tens of thousands of years, with evidence of star representations found in ancient artifacts and cave paintings.
While the constellations we see today are not composed of stars that are physically close to one another, they appear grouped together from our vantage point on Earth. The Greek scientist Ptolemy documented many of these constellations in his influential work, the "Almagest," which served as an astronomical reference for centuries. Throughout history, constellations have taken on additional significance, influencing various cultural practices, including astrology. The International Astronomical Union standardized the constellations in the early 20th century, solidifying their modern boundaries. Notable constellations include Orion, Ursa Major, and Centaurus, each with its own rich history and cultural associations.
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Constellation
A constellation is a group of stars that forms a pattern in the sky and is named after its resemblance to mythological figures, animals, or objects. Most of the modern constellations come from the Ancient Greeks, although their origins almost certainly date back before recorded human history. The stars that make up the patterns are not near each other in space but seem to be grouped together only from the perspective of Earth. There are eighty-eight official constellations, each assigned a specific area of the night sky. Among the various figures set in the heavens are Greek heroes, mythological beasts, the pieces of an ancient ship, a painter's easel, and even strands of a queen's hair.
History
The exact origin of the constellations is unclear, but researchers have traced mankind's fascination with the night sky as far back as tens of thousands of years. In 1979, archeologists unearthed an ivory mammoth tusk dating from about 32,500 years ago that seems to show the figure of the constellation Orion, the hunter. Images of star patterns have also been discovered on cave paintings in France and Spain from 14,000 to 16,500 years ago.
Many of today's more recognizable constellations have their origins in the Sumerian and Babylonian civilizations of the third or fourth millennia B.C.E. The Babylonians also recorded the constellation Orion and referred to it as a heroic hunter figure. About 3000 B.C.E., the Egyptians observed the constellation Scorpius, and called it "the scorpion king." These ancient cultures would not have seen the exact same star patterns that exist today. Because of a slight wobble in Earth's rotation, called precession, the planet's axis has shifted over thousands of years, altering the positions of stars in the sky.
The Greeks undoubtedly inherited their knowledge of the constellations from the Egyptians, who received theirs from the Babylonians. The poet Homer made the first Greek references to constellations in his Iliad and Odyssey around 750 BCE, describing Orion; Boötes, the herdsman; and Ursa Major, the great bear. About the year 150 CE, the Greek scientist Ptolemy combined his own observations with older scientific works in the Almagest, a book detailing the existing astronomical knowledge of the era.
Ptolemy listed forty-eight star patterns, including twenty-one found in the northern skies, fifteen in the southern, and the twelve constellations of the zodiac. The zodiac constellations—Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpius, Sagittarius, Capricornus, Aquarius, and Pisces—lie along a path of sky called the ecliptic. The sun, moon, and planets appear to move through the ecliptic, which is the projection of Earth's orbit around the sun on the celestial sphere. Ancient cultures often gave these constellations divine importance, leading to the pseudoscience of astrology and the development of the horoscope. Most of Ptolemy's forty-eight constellations are still used in the modern era, except for Argo Navis, the ship sailed by Jason and the Argonauts in Greek myth. The constellation was later broken up into smaller pieces, such as its sail, stern, and keel.
The Almagest was considered an astronomical standard for more than a millennium. By the sixteenth century, European trading vessels were sailing the southern seas and discovering new star patterns unknown to the Greeks. Advancements in optical technology also made fainter stars visible for the first time. A German astronomer added two new constellations in 1536, including Coma Berenices, named after the hair of Egypt's Queen Berenice. Almost sixty years later, a Dutch astronomer began mapping the southern sky, cataloging several new star patterns. Other astronomers in the ensuing centuries added even more constellations. Many of these patterns were given names based on technology of the day: Circinus, the compass; Pictor, the painter's easel; and Sextans, the sextant. Constellations were even used to curry favor from royalty. British astronomers of the seventeenth and eighteenth centuries tried to introduce Robur Carolinum (Charles' Oak), in honor of King Charles II, and Psalterium Georgii (George's Harp), for King George III.
By the early twentieth century, there were many star catalogs being published, often with overlapping or competing constellations. In 1922, the International Astronomical Union decided to standardize the night sky and agreed upon eighty-eight official constellations and their boundaries. The changes were approved in 1930.
Notable Constellations
Orion: Orion is the hunter, who legend says was placed in the heavens by the gods after being stung by Scorpius. Orion is one of the most recognizable patterns in the sky and is famous for its three-star "belt" and the Orion Nebula, a cloud of gas and dust where new stars are formed. The ancient Egyptians associated Orion with the god Osiris.
Canis Major: The "greater dog" is one of Orion's two hunting dogs. The constellation contains Sirius, the brightest star in the sky other than the sun.
Centaurus: Centaurus is named after Chiron, the king of the centaurs, who was accidentally killed by Hercules and placed in the sky as a reward from Zeus. Centaurus is a large constellation visible only in the Southern Hemisphere and contains more than one hundred stars, including two of the sky's top ten brightest.
Ursa Major: The "great bear" is a large constellation in the northern sky. It contains the famous group of seven stars known as the Big Dipper, which makes up the bear's "tail." The Big Dipper is an asterism, a group of stars within a constellation. The Big Dipper is one of the oldest known star patterns. The Chinese saw it as a chariot for the Emperor of Heaven; in Britain it was a plow; in France it was a saucepan; and to the Mayans it was a legendary parrot named Seven Macaw.
Hydra: Named after the legendary serpent slain by Hercules, Hydra is the largest constellation, snaking across more than 3 percent of the sky.
Bibliography
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