8: Stellar Tracking
- Page ID
- 115282
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The stars of the Milky Way orbit around the center of the galaxy. This means that the Sun and the stars are all in constant motion. Some of that motion is relative motion, or motion that is moving other objects towards or away from the Sun and also side to side from our perspective. Given that the stars are extremely far away, how can astronomers measure their movement? How can they measure the distance to the stars? This chapter is about the many different methods that astronomers use to measure the distance and motion of the stars.
By the end of this section, you will be able to:
- Explain how the Doppler effect works
- Describe how astronomers use the Doppler effect to calculate radial velocity
- Describe the concept of triangulating distances to distant objects
- Define the proper motion of a star
- Describe how astronomers need a star's radial velocity, transverse velocity, and distance, to calculate a star's space velocity
- Describe how astronomers use parallax to measure the distance to stars
- Describe how astronomers use variable stars to measure the distance to stars
- Explain how spectral types are used to estimate stellar luminosities
Thumbnail: This sketch, called extrapolating sun distance by stars, was published in Popular Science Monthly Volume 10 covering material from 1876 to 1877. The sketch demonstrates the use of parallax to measure the distance to the Sun, establishing the length of the astronomical unit (AU). ("Extrapolating sun distance by stars," Unknown Author, Public Domain via Wikimedia Commons)