A photo of the night sky with stars

Have you ever looked up at the night sky and noticed patterns in the stars? These collections of stars making up that image is called a constellation. Constellations are a group of stars that form an image when connected with imaginary lines.

Constellations have been used for thousands of years by navigators and storytellers all over the world. The names and images of the constellations were recorded by an astronomer named Ptolemy in a book called the Almagest. One thousand years after Ptolemy, a Persian astronomer named al-Sufi translated Ptolemy鈥檚 work into Arabic and expanded it by including his own scientific observations to the book. Al-Sufi's book was also published in Latin which was the official language of the scientific community. That is why Arabic, Latin, and Greek works are commonly associated with constellations and stars.

What constellations you can see depends on what hemisphere you live in and the time of year. There are two hemispheres on Earth that are divided by the equator, known as the Northern and Southern Hemispheres. Because the Earth is tilted on an axis that goes around the sun, the night sky looks different throughout the year.

A celestial map of the southern hemisphere
Graphic showing several constellations
Did You Know?

路 Many of the names of the constellations come from Greek mythology, such as Orion.

路 The International Astronomical Union (IAU) has defined 88 constellations.

路 There are constellations for each of the zodiac signs.

路 The sun is also a star.

路 Magnitude is used as a measurement to gauge a star's brightness.