A constellation is a group of stars that makes a pattern in the sky. The constellations do not change their shape, but as the night passes they seem to move around the sky. If you watch carefully, you will see that they appear to move in a circle around a center point. In the northern hemisphere, that center point is the North Star, also known as the Pole Star, or Polaris. The North Star is above the North Pole. 

But the stars are not really moving. We are moving. The Earth is rotating, and that makes all the stars appear to rotate.

What is a constellation?

What are two other names for the Pole Star?   and 
Why do the stars seem to rotate around the sky?

For thousands of years, people have looked up at the sky and wondered about what they saw. They played a game by connecting the stars and creating pictures. They imagined people, animals, and gods in the heavens.

But for many of these people so long ago, this was not really a game.  They needed to know how and when these star pictures moved around the sky. This told them when to plant and harvest their crops. (They didn't have calendars then.) Certain constellations would appear in the spring, and others would appear as the weather was about to get colder. Other ancient people used the stars to guide them at night, especially when they were out on the ocean.

What are two reasons that ancient people imagined star pictures in the heavens? 

Many of the constellations were named by ancient astronomers in Greece, Rome, and Babylonia. They honored the heroes and villains of many of their favorite stories by placing them in the sky.
What do you think an astronomer is?

Here are a few of the well-known constellations 
that we can see in the northern hemisphere.

ORION - the hunter
            This constellations was named after a hunter in an ancient story. It is seen in the winter sky. Orion was the companion of the goddess of the hunt.

PEGASUS - the winged horse
            Perseus rode this magical horse when he saved Andromeda from a sea monster.

AQUARIUS - the water carrier
            Ancient people imagined seeing a man pouring water from a jar.

CANCER - the crab
            The crab was a monster in Greek legends who attacked Hercules.

CANIS MAJOR - the great dog
            This large dog was the faithful companion of Orion, the hunter.

CAPRICORN - the goat
            This creature had the head of a goat and the tail of a fish.  He could travel on both land and sea.

DRACO - the dragon
            Hercules killed this monster in legend.

GEMINI - the twins
            The twins were named Castor and Pollux, the names of the stars that are their heads.  They were devoted brothers.

            The ancient Greeks thought Hercules was the strongest and bravest man on Earth. He killed many monsters.  Many of the monsters he killed are other constellations in the sky.

LEO - the lion
            Leo was the fiercest lion in the world. No weapons would hurt him. So Hercules choked him!

PISCES - the fish
            The fish were imagined to be Venus and Cupid who turned themselves into fish and jumped into a river to escape a monster.

SAGITTARIUS - the archer
            This centaur, half man and half horse, aims his arrow at a giant scorpion.

TAURUS - the bull
            Zeus, according to legend, disguised himself as a white bull to win the love of a princess.

URSA MAJOR - the great bear
            It seems Zeus was hanging out with another woman. His wife did not like that, so she turned the woman into a bear. Within this constellation is the familiar Big Dipper constellation.

URSA MINOR - the little bear
            Zeus turned his son into a little bear and put him in the sky.  This constellation is also know as the Little Dipper.  The North Star is at the end of the handle of the dipper.

VIRGO - the maiden
            Virgo was the Greek goddess of justice.  It is also linked with the goddess of the harvest.

LIBRA - the scales
            To the ancient Romans, this constellation represented the scales of justice.

Look back at the descriptions of Leo, Cancer, and Draco.  What do they have in common?

Click here to see what the sky looks like on a clear night in the northern hemisphere.