Understanding Star Patterns and Constellations

How Identifying Star Patterns Paved the Way for Modern Astronomy

Star chart of constellations and asterisms

ThoughtCo / Carolyn Collins Petersen

Observing the night sky is one of the oldest pastimes in human culture. It likely goes back to the earliest people, who used the sky for navigation; they noticed the backdrop of stars and charted how they changed over the year. In time, they began to tell tales about them, using the familiar look of some patterns to tell of gods, goddesses, heroes, princesses, and fantastic beasts.

The Start of Astronomy

In earlier times, telling stories was the most common form of entertainment, and the star patterns in the sky provided worthy inspiration. People also used the sky as a calendar once they noticed a correlation between the stars in the sky and different times of the year, like changing seasons. That led them to build observatories and temples that guided ritualistic skygazing.

These storytelling and viewing activities were the start of astronomy as we know it. It was a simple beginning: People noticed the stars in the sky and named them. Then, they noticed patterns amongst the stars. They also saw objects moving across the backdrop of stars from night to night and called them "wanderers"—we now know them as planets.

Of course, the science of astronomy grew over the centuries as technology advanced and scientists could define the objects in the sky they were seeing. However, even today, astronomers at all levels use some of the star patterns that were identified by the ancients; they provide a way to "map" the sky into regions.

Stonehenge at sunrise
Brian Bumby / Getty Images

The Birth of the Constellations

Ancient humans got creative with the star patterns they observed. They played cosmic "connect the dots" to establish patterns that looked like animals, gods, goddesses, and heroes, creating constellations. They also created stories to go along with these star patterns, which became the basis for many of the myths that have passed through centuries by the Greeks, Romans, Polynesians, Indigenous Americans, and members of various African tribes and Asian cultures. For example, the constellation Orion inspired an important figure in Greek mythology.

Most of the names we use for constellations today come from ancient Greece or the Middle East, a legacy of the advanced learning of those cultures. But those terms are widespread. For instance, the names "Ursa Major" and "Ursa Minor"—the Big Bear and the Little Bear—have been used to identify those stars by different populations around the world since the Ice Ages.

Star chart for April
A star chart showing three easy-to-spot constellations in April. ThoughtCo / Carolyn Collins Petersen

Constellation Use for Navigation

Constellations played a significant role in navigation for explorers of the earth's surface and oceans; these navigators created extensive star charts to help them find their way around the planet.

Often though, a single star chart wasn't enough for successful navigation. The visibility of constellations can differ between the Northern and Southern Hemispheres, so travelers found themselves having to learn whole new sets of constellations when venturing north or south of their home skies.

Star chart of Alpha Centauri
A star chart view of Alpha Centauri with the Southern Cross for reference. ThoughtCo / Carolyn Collins Petersen

Constellations Versus Asterisms

Most people are familiar with the Big Dipper, but that seven-star pattern is not technically a constellation. Rather, it is an asterism—a prominent star pattern or group of stars that is smaller than a constellation. It can be considered a landmark.

The star pattern that makes up the Big Dipper is technically part of the aforementioned constellation Ursa Major. Likewise, the nearby Little Dipper is a part of the constellation Ursa Minor.

This does not mean that all landmarks are not constellations, though. The Southern Cross—our popular landmark for the south that appears to point toward the earth's South Pole—is a constellation.

Star chart of the Big Dipper
Use the Big Dipper to help you find two other stars in the sky. ThoughtCo / Carolyn Collins Petersen

Constellations Visible to You

There are 88 official constellations in the Northern and Southern Hemispheres of our sky. Most people can see more than half of them throughout the year, though it can depend on where they live. The best way to learn them all is to observe throughout the year and study the individual stars in each constellation.

To identify the constellations, most observers use star charts, which can be found online and in astronomy books. Others use planetarium software such as Stellarium or an astronomy app. There are many such tools available that will help observers make useful star charts for their observing enjoyment.

Star chart showing the southern cross
A star chart showing the southern cross and a nearby star cluster. ThoughtCo / Carolyn Collins Petersen

Fast Facts

  • Constellations are groupings of stars into familiar-looking figures.
  • There are 88 officially recognized constellations.
  • Many cultures developed their own constellation figures.
  • Stars in constellations are not usually close to one another. Their arrangement is a trick of perspective from our point of view on earth.

Sources

  • “International Astronomical Union.” IAU, www.iau.org/public/themes/constellations/.
  • “The 88 Constellations of the Night Sky.” The Taurus Constellation | Learning the Night Sky, Go Astronomy, www.go-astronomy.com/constellations.htm.
  •  "What are Constellations." www.astro.wisc.edu/~dolan/constellations/extra/constellations.html.

Edited and updated by Carolyn Collins Petersen.