Constellation

A constellation is an area on the celestial sphere where a group of stars makes a pattern or outline. This pattern often looks like an animal, a story from long ago, or something that does not move. People have used constellations for thousands of years to tell stories, find their way, and learn about the night sky. The first constellations were probably made in prehistory, and different groups of people made their own star groups.

Twelve or thirteen old constellations are part of the zodiac. The zodiac follows where the Sun, Moon, and planets move in the sky. These constellations started with Babylonian and Chaldean people and later appeared in Greece. Today, the International Astronomical Union says there are 88 official constellations. Each one has its own space in the sky. These help scientists and people who love stars find things in the night sky.

Other star patterns are called asterisms. They are not official constellations but still help with navigation. Examples are the teapot in Sagittarius and the Big Dipper in Ursa Major. Constellations link us to old tales and help us see the amazing things above us.

Terminology

The word constellation means a "set of stars." It comes from a Late Latin word. It entered the Middle English language in the 14th century.

Today, there are officially 88 constellations. Each has a Latin name, as decided by the International Astronomical Union. Some stars in a constellation look close together in the sky, but they can be far apart in space. Over time, these star patterns change slowly as stars move.

Observation

The stars appear in different places in the sky during different times of the year. This happens because the Earth moves around the Sun. As the Earth turns, the sky looks like it spins. Stars move in circles around the north and south pole stars.

The Milky Way goes through many star patterns, called constellations. Some of these are Cygnus, Cassiopeia, Orion, Puppis, and Vela. In the northern sky, Polaris, also called the North Star, helps point toward north. In the southern sky, Sigma Octantis is near the south pole but it is hard to see.

History of the early constellations

Main articles: Old Babylonian astronomy, Egyptian astronomy, Ancient Greek astronomy, Chinese constellations, Chinese astronomy

People have grouped stars into patterns called constellations for thousands of years. These patterns often looked like animals, objects, or stories important to a culture.

The earliest proof that people used constellations comes from stone writings in Mesopotamia around 3000 BC. These early patterns helped shape later Greek constellations. In ancient Babylon, detailed lists of stars and constellations were made during the Middle Bronze Age. The Greeks later used many of these Babylonian constellations.

Ancient China also made its own set of constellations. They recorded these on special bones from the Shang dynasty and later organized them during the Han period. These Chinese constellations were different but sometimes had similarities with Babylonian ones.

Early modern astronomy

Most northern constellations have names from ancient Greek stories. People have used these names for a very long time. We know about them from old star charts, like one shown on a statue called the Farnese Atlas. Southern constellations were created later, mostly when sailors needed to find their way using the stars.

In 1603, a book called Uranometria by Johann Bayer gave each star in a constellation a Greek or Latin letter. This helped organize the stars into groups. Later, in 1922, astronomers agreed on 88 constellations that we still use today. These include both old Greek names and newer names for the southern sky.

Dark cloud constellations

Further information: Great Rift (astronomy) and Molecular cloud § List of molecular cloud complexes

Some cultures saw shapes in dark patches of the night sky. For example, the Inca people saw animals there. In Australian Aboriginal astronomy, one famous dark shape is called the "emu in the sky." Its head is formed by the Coalsack, a dark area in the sky.

List of dark cloud constellations

• Great Rift (astronomy)
  • Cygnus Rift
  • Serpens–Aquila Rift
  • Dark Horse (astronomy)
  • Rho Ophiuchi cloud complex
  • Emu in the sky