Constellations

Constellations are groups of stars which people have imagined form certain pictures in the sky. They have helped people from ancient times to tell time and find their way at night. The stars in constellations look like they are near each other in space and the same distance from Earth, but they are not. One star in a constellation can be much closer to the Earth than another.

The ancient Babylonians, Chinese and Egyptians first recorded stars and their movements. The ancient Babylonians grouped stars into constellations and even made a calendar. An astronomer studies the sky and everything in it. The most famous Greek astronomer was Ptolemy. His book, the Almagest, written in 150 A.D., included the known constellations.

Ptolemy wrote about 48 constellations, but more would be found later in history. Sailors used the constellations to help them find their way at night. When the telescope was discovered in the 1600's, astronomers discovered more stars and named more constellations. In 1687 Johannes Hevelius invented seven new constellations.

Some stars came to be listed in more than one constellation, so astronomers decided to organize the constellations. In 1930, the IAU (International Astronomical Union) made an official list of 88 constellations. The night sky was divided into 88 sections, one for each constellation.

Each constellation has a name. The names for many of these come from Greek myths or stories. The stories tell how the stars came to be where they are. Ursa Major, known as the Great Bear, appears in the Northern Hemisphere. The Big Dipper is a star pattern in this constellation. It looks like a long-handled ladle. The myth tells that the Greek goddess Hera was jealous of a woman named Callisto and turned her into a bear. The god Zeus, her boyfriend, carried her off to the sky before she could be killed by a hunter. The constellation looks like a bear.

Ursa Minor is called the Little Bear. A star pattern within Ursa Minor is called the Little Dipper. At the end of the handle is Polaris, the North Star. It sits right above the North Pole, so it seems not to move. It has guided people for thousands of years. The Big Dipper and Little Dipper are called asterisms. Each is a part of a constellation but not an official constellation.

When different people of the world view the constellations, they may see different objects. Where European astronomers saw the constellation Leo as a lion, the ancient Chinese thought they saw a horse. Sometimes different cultures saw almost the same thing. The Iroquois tribe in America looked at Ursa Major and saw a bear too, but they didn't give the bear a long tail like the Greeks. They thought the stars were hunters chasing the bear.

Other peoples in the world thought that stars were gods. The Maori tribe of New Zealand thought that the god Maui used the constellation Scorpius as a fishhook. He is said to have pulled up one of the islands of New Zealand from the ocean using that hook.

In summary, constellations are groups of stars which seem to form a pattern or picture in the night sky. For thousands of years, people have used these constellations to guide them in their travels. Some have incorporated them into their religions. The constellations have been named mainly from stories in Greek mythology. 88 constellations were officially named in 1930. They are varying distances from Earth.