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?
A) The star is moving toward us.
B) The star is moving away from us.
C) The star is getting hotter.
D) The star is getting colder.

Question

Quizplus · Accepted Answer

The observed wavelength is slightly shorter than the laboratory measurement, indicating a blueshift. This suggests the star is moving toward us.

Laboratory Measurements Show Hydrogen Produces a Spectral Line at a Wavelength