* Moving Towards Earth: The light waves from the star are compressed, causing the wavelengths to shift towards the blue end of the spectrum. This is called blueshift.
* Moving Away From Earth: The light waves from the star are stretched, causing the wavelengths to shift towards the red end of the spectrum. This is called redshift.
How it works:
Imagine a star emitting light waves like sound waves from a siren. If the siren is moving towards you, the sound waves are compressed, making the pitch higher. If the siren is moving away from you, the sound waves are stretched, making the pitch lower.
The same principle applies to light waves. When a star is moving towards Earth, its light waves are compressed, making the light appear bluer. When a star is moving away from Earth, its light waves are stretched, making the light appear redder.
Measuring the Doppler Shift:
Astronomers can measure the Doppler shift of a star's spectrum to determine its radial velocity (the speed at which it is moving towards or away from Earth). This information helps us understand:
* Stellar motion: How stars move within galaxies and how galaxies move within the universe.
* Expansion of the universe: The redshift of distant galaxies provides evidence for the expansion of the universe.
* Exoplanet detection: The Doppler shift of a star's light can be used to detect the gravitational pull of orbiting planets.
In summary: A star moving towards Earth experiences a blueshift, while a star moving away from Earth experiences a redshift. This phenomenon, known as the Doppler effect, is a powerful tool in astronomy for understanding the motion of celestial objects.
