From laboratory measurements, we know that a particular spectral line formed by hydrogen appears at a wavelength of 486.1 nanometers (nm). The spectrum of a particular star shows the same hydrogen line appearing at a wavelength of 485.9 nm. What can we conclude?
- The "star" actually is a planet.
- The star is moving away from us.
- The star is getting colder.
- The star is getting hotter.
- The star is moving toward us.