Laboratory measurements show hydrogen produces a spectral line at a wavelength of 486.1 nanometers (nm). A particular star's spectrum shows the same hydrogen line at a wavelength of 486.0 nm. What can we conclude?

Question

Quizplus · Accepted Answer

The observed shift in the wavelength of the hydrogen spectral line from 486.1 nm to 486.0 nm indicates a blueshift, which means the star is moving toward us. This is because the wavelength of light decreases (shifts towards the blue end of the spectrum) when the source of the light is moving towards the observer, according to the Doppler effect.

Laboratory Measurements Show Hydrogen Produces a Spectral Line at a Wavelength