Module 2: Constellations

Constellations are sets of stars that look like mythological beasts, people, objects that look nothing like their namesakes. They are patterns of stars that were recognized by ancient cultures and connected together in different ways according to the culture's stories or myths. The night sky changes, but the patterns have remained the same for thousands of years.

It is hard to believe that the stars are so far away and most are not even close to one another. To people on Earth, however, they appear to be next to other stars in the celestial sphere as constellations. In addition to constellations, there are star patterns that are easy to identify because of their patterns but are not classified as constellations. You may know some of them already, such as the Big Dipper, the Great Square of Pegasus, the Summer Triangle, and the Winter Hexagon. Furthermore, brighter stars in the night sky are usually named.

Because people can see more than 1,500 stars on any given night with a dark, clear sky, finding an individual star can be quite difficult. Beyond their names, there is also another way to identify individual stars, by Greek letters. The brightest star is usually identified by the Greek letter alpha. There are exceptions but the brightest star is usually the alpha star, the second brightest is beta, and so on. This helps to tell the relative brightness or magnitude of the star in the constellation where as a name has no specific meaning for brightness. Brightness can be quite difficult to identify. This is why we use the term intensity to more accurately measure the brightness of a star. Finding magnitudes can be tricky but there are formulas that astronomers use to more accurately measure the differences in intensity of stars. Astronomers use a variety of tools to locate stars and constellations, including planispheres and sky maps. Planetariums are used to show images of the night sky on a dome-shaped screen so as to replicate the feeling and vision of really being within space.

Getting Started

Finding a constellation is much like completing an activity of connecting the dots. Study the first image below. Can you find the constellation of Hercules within the stars? After taking time to find the stars that make up the shape of Hercules, review the second image to see the constellation.

Key Vocabulary

To view the definitions for these key vocabulary terms, visit the course glossary