How does astrometry differ from the doppler effect?

Question

Anna Armstrong · Accepted Answer

Astrometry is measurement of positions of astronomical objects whereas the Doppler effect is one of the key tools used in Astrometry.

The measurement of astronomical objects' positions and velocities is known as astrometry. One instrument used in astrometry is the Doppler effect, which bears the name of the physicist Christian Doppler. Strong gravitational fields also cause objects' spectra to be red shifted. For instance, different elements produce characteristic emission or absorption lines in the spectra of stars or galaxies, but we observe these lines shifted towards higher (blue) or (more commonly) lower (red) ends of the spectrum. This frequency shift roughly corresponds to the velocity with which the observed object is moving towards or away from us. Red shift gives us an approximate measure of an object's distance from us because it is a function of the universe's expansion form, which means that objects that are farther away from us are also moving away from us faster and are therefore generally more red shifted.

Henry Asbill · Answer

undefined The Doppler effect is the change in a wave's frequency or wavelength with respect to an observer moving in relation to the wave source, whereas astrometry measures the positions and movements of celestial objects, such as stars.