⚙️ how
How do astronomers know a star is moving toward or away from Earth?
SpaceAstronomy
Quick Answer
They use the Doppler shift of the star’s spectral lines. Lines shifted toward blue mean approach; shifted toward red mean recession.
The Full Story
The Doppler effect changes the wavelength of light when a source moves relative to the observer. In stellar spectroscopy, the pattern of absorption lines shifts slightly depending on whether the star is coming closer or moving away. This allows astronomers to measure radial velocity, often to within meters per second with modern instruments. The same technique also helps find exoplanets by detecting a star’s tiny wobble caused by an orbiting planet.
Key Facts
1.Blue shift indicates approach
2.Red shift indicates recession
3.Radial velocities can be measured very precisely with spectrographs
YouTube Angle
Suggested video title for this topic:
"How a star’s color-shift reveals its motion"