Stellar Properties

Review 17.1 The Brightness of Stars to understand how the total energy emitted by a star, known as luminosity, and its distance from Earth determine its apparent brightness.
Watch the video Magnitude and Luminosity for an explanation of the magnitude system.
Explore 17.2 Colors of Stars to learn about the relationship between the color of stars and their temperature, as well as how astronomers measure and express star temperature using color indexes.
Watch the video Star Colors to see the connection between blackbody radiation and the colors of stars in the night sky. The key factor to remember is that star color is just another way of talking about the temperature of the star.
It may not seem like much, but measuring a star’s luminosity and temperature can tell us an enormous amount about the star, including its mass, radius, and even how the star has changed over time.