Doppler shift

Definition

The Doppler shift is the change in frequency or wavelength of light from a source due to its motion relative to an observer. It is commonly used in astronomy to determine the movement and velocity of celestial objects.

5 Must Know Facts For Your Next Test

1. The Doppler shift can indicate whether an object is moving towards or away from Earth, known as blue shift and red shift respectively.
2. In the context of quasars, a significant redshift indicates that these objects are moving away at high speeds, suggesting they are at great distances.
3. The magnitude of the Doppler shift can be used to calculate the velocity of stars orbiting black holes, providing indirect evidence for their existence.
4. Active galaxies often exhibit strong Doppler shifts in their spectral lines due to the rapid motion of gas near supermassive black holes.
5. The study of Doppler shifts in light from distant galaxies has been crucial in understanding the expansion rate of the universe.

Review Questions

• How does the Doppler shift help astronomers determine if a celestial object is moving towards or away from Earth?
• Why is the detection of redshift important when studying quasars?
• How can Doppler shifts provide evidence for black holes?

Related terms

Redshift: The displacement of spectral lines towards longer wavelengths, indicating an object is moving away from the observer.

Blueshift: The displacement of spectral lines towards shorter wavelengths, indicating an object is moving towards the observer.

Spectral Lines: Specific wavelengths within a spectrum that correspond to particular transitions in atoms or molecules, used to identify chemical composition and velocities.