The Doppler Effect

Doppler Shift Equation

Redshift/blueshift tell us direction. the amount of the shift tells us speed. distance doesn't play a role.

an absorption spectrum that is blueshifted relative to a stationary star.

a bright star is moving toward earth. if you were to look at the spectrum of this star, what would it look like.

Transverse motion or proper

across the line-of-sight.

Doppler Effect

an increase (or decrease) in the frequency of sound, light, or other waves as the source and observer move toward (or away from) each other. The effect causes the sudden change in pitch noticeable in a passing siren, as well as the redshift seen by astronomers.

Longer wavelength

gets longer and the light becomes redder.

Compressed wavelength

gets shorter and becomes bluer.

Radial motion

line-of-sight movement.

shift toward longer wavelengths

when a source is moving away from you, the doppler effect causes the light to.

Source and Observer

when they are moving away from each other, waves get stretched out.

Source and observer

when they are moving toward each other, waves get compressed.

the will have the same blueshift

you are in a spaceship flying toward two stationary stars. Star A is really far away and Star B is nearby. Which star will have the largest blueshift?

Both are moving with the same speed

you observe two redshifted spectra. What is their speed?