Introductory Astronomy: Stellar Properties

Stars are the keys to understanding the secrets of the Universe. It is by studying the stars that astronomers learn about the formation of planets, the origin of the elements, the characteristics of galaxies, and the future of our Solar System. Unfortunately, because stars are so far away, it is difficult to determine their properties. For example, if an astronomer wants to know how big a certain star is, he obviously can't walk up to it and measure it with a measuring tape. Because of this difficulty, astronomers have learned to be very tricky and to use a star's light and motion to determine many of its properties. This page will describe three important properties of stars and how astronomers determine them.

There are three basic properties of a star that we measure:

  1. The Spectrum (or color)
  2. The Apparent Brightness (or flux)
  3. The Parallax (which gives us the distance)

From these, we can learn many important things about the star. For example, from the star's spectrum, we can find its: Composition and Surface Temperature. From the apparent brightness and distance, we can find its: Luminosity (or absolute magnitude). Then, from its surface temperature and luminosity, we can find its: Radius (and mass).

After you review these sections, try a few sample questions to test your understanding. These questions are typical of questions given in introductory astronomy course exams. They are meant only to give you an idea of what kinds of questions MIGHT be on your exam. Just because these questions are here does NOT mean that you will have questions like them on your exam, NOR does it even mean that you will have questions on these topics on your exam. They are just PRACTICE questions!