Constellation

A constellation is a group of stars that form a longrecognized pattern in the sky. The names of many constellations are Greek in origin and are related to ancient mythology. (The ancient Chinese astronomers also divided stars into constellations that, today, are called Xiu, or mansions.) The stars that make up a constellation may be at very different distances from the Earth and from one another. The pattern is one that humans choose to see and has no physical significance. In fact, in three-dimensional space, most of the stars within a constellation are far distant from one another—having little or nothing in common with respect to their distance from Earth or from one another.

Novice stargazers are often taught that the pattern of stars in a constellation resembles an animal or a person engaged in some activity. For example, Sagittarius is supposed to be an archer, Ursa Major a large bear, and Ursa Minor a small bear. However,

most people locate Sagittarius by looking for a group of stars that resemble an old-fashioned coffee pot. Ursa Major is more commonly seen as a Big Dipper and Ursa Minor as a Little Dipper. In fact, it is more likely that ancient stargazers named constellations to honor people, objects, or animals that were a part of their mythology, not because they thought the pattern resembled the honoree.

Today, the International Astronomical Union divides the stars in the sky into 88 constellations that are used by astronomers to identify regions where stars and other objects are located in the celestial sphere (sky). Just as a person might tell someone that Pike’s Peak is near Colorado Springs, Colorado, so an astronomer refers to nebula (M 42) as the Orion Nebula or speaks of galaxy M 31 in Andromeda and the globular cluster M 13 in Hercules.

The constellations seen in the Northern Hemisphere’s winter sky—Orion, Taurus, Canis Major, and others—gradually move westward with time, rising above the eastern horizon approximately four minutes earlier each evening. By late spring and early summer, the winter constellations are on the western horizon in the early evening and Leo, Bootes, Cygnus, and Sagittarius dominate the night sky. In the fall, Pegasus, Aquila, and Lyra brighten the heavens. A number of polar constellations (Cephus, Cassiopeia, and Ursa Minor in the north and Crux, Centaurus, and Pavo in the south) are visible all year as they rotate about points directly above the North and South Poles.

The westward movement of the constellations is the result of Earth’s motion along its orbit about the sun. With each passing day and month, humans see a different part of the celestial sphere at night. From this frame of reference, on a planet with a tilted axis, the sun, moon, and planets follow a path along the celestial sphere called the ecliptic, which makes an angle of 23.5° with the celestial equator. As the sun moves along the ecliptic, it passes through 12 constellations, which ancient astronomers referred to as the Signs of the Zodiac—Aries, Taurus, Gemini, Cancer, Leo, Libra, Scorpius, Sagittarius, Capricorn, Aquarius, and Pisces. The planets also move along the ecliptic, but because they are much closer to the Earth than the stars, their paths change with respect to the constellations. These wanderers, which is what the ancients called the planets, led to astrology—the belief that the motion of the sun, moon, and planets along the zodiac has some influence on human destiny. While there is no evidence to support such belief, the pseudoscience of astrology led to the careful observations of early astronomers.

See also Celestial coordinates; Milky Way; Star.

Constellation

A constellation is a group of stars that form a long-recognized pattern in the sky, as viewed from Earth. The stars that make up a constellation do not represent any meaningful order in the universe. Those stars may be at very different distances from Earth and from one another. Constellations seen from Earth would be shaped much differently and would be unrecognizable if viewed from another part of our galaxy.

The naming of constellations dates back to ancient civilizations. Although some constellations may resemble the animals, objects, or people for which they were named, others were merely named in honor of those figures. Many of the constellations were originally given Greek names and are related to ancient mythology. These names were later replaced by their Latin equivalents, names by which they are still known today.

Words to Know

Asterism: Familiar star pattern that is not a constellation.

Celestial sphere: The sky or imaginary sphere that surrounds Earth and provides a visual surface on which astronomers plot celestial objects and chart their apparent movement due to Earth's rotation.

Ecliptic: The apparent path of the Sun, the Moon, and the major planets among the stars in one year, as viewed from Earth.

Stargazing, however, was not limited to the ancient Greeks and Romans. Many cultures looked to celestial bodies to understand the creation

and structure of the universe and their place in it. Their naming of the different stars reflects their views or mythology. For example, the constellations the Romans called Ursa Major and Cassiopeia (pronounced kas-eeo-PEE-a) were called Whirling Man and Whirling Woman by the Navajo.

Some familiar star groups known by common names are not constellations at all. These groups are called asterisms. Two examples are the Big Dipper and the Little Dipper. The Big Dipper, also known as the Plough, is part of the constellation Ursa Major (the Great Bear). The Little Dipper is part of the constellation Ursa Minor.

Eighty-eight constellations encompass the present-day celestial sphere (the sky or imaginary sphere that surrounds Earth). Each of these constellations is associated with a definite region in the celestial sphere. The yearly path of the Sun, the Moon, and the major planets among the stars, as viewed from Earth, is called the ecliptic. Twelve constellations are located on or near the ecliptic. These constellations—Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricornus, Aquarius, and Pisces—are known as the constellations of the zodiac. The remaining constellations can be viewed in the celestial sphere during the year from either the Northern Hemisphere (28 constellations) or the Southern Hemisphere (48 constellations).

The daily rotation of Earth on it axis causes the constellations to appear to move westward across the sky each night. The yearly revolution of Earth around the Sun, which brings about the seasons, causes different constellations to come into view during the seasons.

[See also Star ]

Constellation

A constellation is a group of stars that form a long-recognized pattern in the sky. The names of many constellations are Greek in origin and are related to ancient mythology. The stars that make up a constellation may be at very different distances from the earth and from one another. The pattern is one that we as humans choose to see and has no physical significance.

Novice stargazers are often taught that the pattern of stars in a constellation resembles an animal or a person engaged in some activity. For example, Sagittarius is supposed to be an archer, Ursa Major a large bear, and Ursa Minor a small bear. However, most people locate Sagittarius by looking for a group of stars that resemble an old-fashioned coffee pot. Ursa Major is more commonly seen as a Big Dipper and Ursa Minor as a Little Dipper. In fact, it is more likely that ancient stargazers named constellations to honor people, objects, or animals that were a part of their mythology and not because they thought the pattern resembled the honoree.

Today's modern stars divide the sky into 88 constellations that are used by astronomers to identify regions where stars and other objects are located in the celestial sphere (sky). Just as you might tell someone that Pike's Peak is near Colorado Springs, Colorado, so an astronomer refers to nebula (M 42) as the Orion Nebula, or speaks of galaxy M 31 in Andromeda and the globular cluster M 13 in Hercules.

The constellations that you see in the Northern Hemisphere's winter sky—Orion, Taurus, Canis Major, and others—gradually move westward with time , rising above the eastern horizon approximately four minutes earlier each evening. By late spring and early summer, the winter constellations are on the western horizon in the early evening and Leo, Bootes, Cygnus, and Sagittarius dominates the night sky. In the fall, Pegasus, Aquila, and Lyra brighten the heavens. A number of polar constellations (Cephus, Cassiopeia, and Ursa Minor in the north and Crux, Centaurus, and Pavo in the south) are visible all year as they rotate about points directly above the North and South Poles.

The westward movement of the constellations is the result of Earth's motion along its orbit . With each passing day and month, we see a different part of the celestial sphere at night. From our frame of reference on a planet with a tilted axis, the sun , moon and planets follow a path along the celestial sphere called ecliptic, which makes an angle of 23.5° with the celestial equator. As the sun moves along the ecliptic, it passes through 12 constellations, which ancient astronomers referred to as the Signs of the Zodiac—Aries, Taurus, Gemini, Cancer, Leo, Libra, Scorpius, Sagittarius, Capricorn, Aquarius, and Pisces. The planets also move along the ecliptic, but because they are much closer to us than the stars constellations along the zodiac their paths change with respect to the constellations. These wanderers, which is what the ancients called the planets, led to astrology—the belief that the motion of the sun, moon, and planets along the zodiac has some influence on human destiny. While there is no evidence to support such belief, the careful observations of early astronomers owes much to the pseudoscience of astrology.

See also Celestial coordinates; Milky Way; Star.

con·stel·la·tion / ˌkänstəˈlāshən/ • n. a group of stars forming a recognizable pattern that is traditionally named after its apparent form or identified with a mythological figure. Modern astronomers divide the sky into eighty-eight constellations with defined boundaries. ∎  a group or cluster of related things.ORIGIN: Middle English (as an astrological term denoting the relative positions of the “stars” (planets), supposed to influence events): via Old French from late Latin constellatio(n-), based on Latin stella ‘star.’

constellation †(astrol.) relative position of the stars; (astron.) number of fixed stars artificially grouped together. XIV. — (O)F. — late L. constellātiō, -ōn-, f. CON- + stella STAR; see -ATION.