The constellations have been called humanity's oldest picture book. For 5,000 and more years, people have looked into a clear night sky and seen the same stars we see today. They isolated groups of stars and connected them to each other with imaginary lines, much as we play connect-the-dots.

In the past, people had an excellent knowledge of the night sky. They were able to tell when to plant and when to harvest, and later they navigated the seas with the stars' help. Characters of myth and legend were used to name and tell the stories of the stars. Here are a few.

The group of stars that looked like a man with a sword was named Orion, for the famous hunter in Greek mythology. The pattern that looked like twin boys they called Gemini, the Twins. The large, bright group of stars in the shape of a lion is known as Leo. According to Greek mythology, Leo was the fierce lion killed by Hercules.

There are millions of stars, but only 5,780 are visible to the naked eye. The largest constellation is Hydra, the Sea Serpent. The smallest constellation is Crux, the Southern Cross.

Twelve constellations, together called the Zodiac, form a belt around the earth. As the earth revolves around the sun, a different part of the sky becomes visible until, after a year, the earth has completed one trip and starts again. Each month, one of the 12 constellations appears above the horizon in the east to begin its march across the sky. Night after night, the constellation appears to move across our sky until it disappears below the horizon in the west and the next constellation appears in the east.

The word Zodiac comes from both Greek and Latin. It means “circle of figures” or “circle of life.” According to the ancient Romans, the year began on the spring equinox, with Aries.

Aries (The Ram)

March 21-April 19

In Greek mythology, Aries was a winged ram with golden wool. His hide became the much-desired golden fleece.

Taurus (The Bull)

April 20-May 20

Jupiter, the supreme Roman god, turned himself into a bull when he swam from Phoenicia to Crete.

Gemini (The Twins)

May 21-June 20

This constellation reminded the Greeks of Castor and Pollux, the mythological twin sons of Zeus. It was thought to bring good luck to sailors since it appeared at the end of the winter storm season.

Cancer (The Crab)

June 21-July 22

Cancer represents the crab that Juno, queen of the gods, sent to rescue Hydra. But Hercules stepped on the crab, crushing it to death. To reward the crab for its heroic attempt, Juno chose it to represent this constellation.

Leo (The Lion)

July 23-August 22

This large constellation honors the strength and bravery of the lion.

Virgo (The Virgin)

August 23-September 22

Virgo is traditionally depicted as a maiden holding an ear of grain to symbolize the harvest.

Libra (The Scales)

September 23-October 22

Libra is the symbol of balance. This constellation appears at the time of the autumnal equinox, when days and nights are equal.

Scorpio (The Scorpion)

October 23-November 21

In mythology, Scorpio (or Scorpius) was the scorpion that attacked and killed the hunter Orion.

Sagittarius (The Archer)

November 22-December 21

This constellation is usually pictured as Chiron the archer, who is a centaur (half man, half horse). Chiron is said to be aiming his arrow at Scorpio to avenge the death of Orion.

Capricorn (The Sea Goat)

December 22-January 19

In many cultures, Capricorn has the head of a goat and the tail of a fish. The goat, an expert climber, represents the sun's climb from its lowest position in the sky. After December 22, the shortest day, the sun's time in the sky increases daily.

Aquarius (The Water Bearer)

January 20-February 18

The Babylonians believed that this group of stars represented an old man pouring water from a jar. The Greeks saw Ganymede, the cup bearer of the gods, who poured the water of life.

Pisces (The Fishes)

February 19-March 20

Pisces represents Venus, the Roman goddess of love and beauty, and her son Cupid. To escape from a monster, they turned into fish and jumped into a river.