When the galaxy moves away from the blue planet, its spectrum shifts towards longer wavelengths. This means that the lines in the spectrum, which indicate specific wavelengths of light emitted by the galaxy, appear to shift towards the red end of the spectrum. The shift is known as a redshift.
On the other hand, when the galaxy moves towards the blue planet, its spectrum shifts towards shorter wavelengths. The lines in the spectrum appear to shift towards the blue end of the spectrum. This shift is known as a blueshift.
Overall, as the galaxy moves away from the blue planet, its spectrum shows a redshift, indicating that the light from the galaxy is being stretched towards longer wavelengths. Conversely, as the galaxy moves towards the blue planet, its spectrum shows a blueshift, indicating that the light is being compressed towards shorter wavelengths.
Open the Shifting Light Spectra activity. When prompted, use the slider to move the galaxy as directed. Describe how the galaxy’s spectrum changes as it moves away from and toward the blue planet.
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