What Are Star Constellations?

Star constellations are star groupings or patterns that appear to form a recognizable shape and are named for such. However, the stars in a constellation are unrelated except for their proximity to one another.

Purpose

The purpose of star constellations is to help astronomers map out the sky and identify certain stars.

Identification

Some constellations, such as the big and little dippers, are easily identified due to their tell-tale shape. The constellation Orion is popular for three of its stars that are lined up perfectly in a row known as Orion's Belt.

History

Constellations have been documented by the Sumerians, Babylonians, Ancient Egyptians and Ancient Greeks. Half of the 88 constellations recognized by the International Astronomical Union were first described by the Greeks. Twelve of these include the constellations of the Zodiac.

Fixed Stars

Constellations may appear different now than they did to our ancestors thousands of years ago. Although they are described as 'fixed stars', stars do move, but not at a rate high enough to be visible within a person's lifetime.

Circumpolar vs. Seasonal Constellations

Some constellations are visible all year while others only appear during specific seasons. For example, in the Northern hemisphere, the big and little dippers are can be seen year-round, but Orion is visible only in the winter.

References

• UCAR: Constellations
• Windows to the Universe: Stars and Constellations
• Students for the Development and Exploration of Space: Constellation Families

Resources

• International Astronomical Union (IAU)