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Chapter 5: Problem 22

What is the Doppler effect? Why is it important to astronomers?

Short Answer

Expert verified
The Doppler Effect is the change in frequency or wavelength of a wave for an observer moving relative to its source. It is important to astronomers as it enables the measurement of velocities of distant celestial bodies, the discovery of exoplanets, and supports our current understanding that the universe is expanding based on the redshift seen in light from distant galaxies.

Step by step solution

01

Understanding The Doppler Effect

The Doppler Effect, named after the Austrian physicist Christian Doppler, refers to the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source. For example, if a source of sound is moving towards an observer, they will perceive the sound as being higher in pitch (higher frequency) than it actually is. If the source of sound is moving away from the observer, they will perceive it as being lower in pitch (lower frequency). The same effect occurs with light waves.
02

The Doppler Effect in Astronomy

This is important in the field of astronomy as it allows for the measurement of speed and direction of distant galaxies or stars relative to the observer on earth. When a star or galaxy is moving away, the light waves emitted undergo a redshift (increase in wavelength or decrease in frequency) as perceived from the observer on earth. When the star or galaxy is moving closer, the opposite happens, a blueshift (decrease in wavelength or increase in frequency) is observed. This provides crucial data about the movement of celestial bodies in the universe.
03

Importance of the Doppler Effect to Astronomers

By measuring the degree of redshift or blueshift, astronomers can determine the speed at which a star or galaxy is moving towards or away from us. More importantly, this effect revealed that the universe is expanding, which is fundamental to our current understanding of the universe. This realization originated from observing a general redshift in light from distant galaxies, indicating they are moving away from us, leading to the formulation of the Big Bang Theory.

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