When a star is approaching Earth, its spectrum is shifted toward which end of the spectrum?

When a star is approaching Earth, its spectrum is shifted toward which end of the spectrum?

• A. Infrared
• B. Blue
• C. Ultraviolet
• D. Red

Answer: (B)

Light from a star forms a spectrum across the colors we can see. If the star is coming toward us, the light waves are squeezed a bit as they travel to Earth, so their wavelengths shorten. That shift to shorter wavelengths is called blueshift, and it moves the spectrum toward the blue end of the visible range. The closer the star is to us, or the faster it moves toward us, the more noticeable the blue shift becomes. If the star were moving away, the spectrum would shift toward the red end (redshift), meaning longer wavelengths.

Light from a star forms a spectrum across the colors we can see. If the star is coming toward us, the light waves are squeezed a bit as they travel to Earth, so their wavelengths shorten. That shift to shorter wavelengths is called blueshift, and it moves the spectrum toward the blue end of the visible range. The closer the star is to us, or the faster it moves toward us, the more noticeable the blue shift becomes. If the star were moving away, the spectrum would shift toward the red end (redshift), meaning longer wavelengths.