How do you measure the red shift of a galaxy?

Answer 1

Hydrogen absorbtion lines in the spectra change position. Measure the change and you have the red shift.

Answer 2

In a continuous spectrum of light (like white light) of stars, there are dark lines. These so-called absorption lines have a fixed frequency and are caused by the absorption of energy when electrons in a specific element jump to a higher state.

Since they only depend on the electron states of elements, the frequency is fixed

If you analyse the light spectrum of a galaxy, you'll find that these absorption lines are not at the position where you expect them, but that they are shifted towards the red end of the spectrum.

The amount of red shift (Doppler effect) gives you the speed at which the galaxy is moving away from us.

Answer 3

First of all.. each element gives off light with specific bands.

so, if you take the light you receive... and you split it up into the rainbow, it will show bands for the various elements that produced it.

the speed of the light-source can be determined by comparing the bands of the light received to the light produced by elements that are stationary...

for example... you find light from the source that has bands where no element would produce such bands.. but.. they are arranged in such a pattern that they look like those of oxygen.. but they are all shifted down in frequency... this is the red shift... and how far these bands have shifted.. depends upon the speed of the source.. away from us.. if it was moving toward us.. there would be a blue-shift

note.. the red shift of one part of a galaxy is different from that of another part.. because of the rotation.

Answer 4

The red shift is the wavelength of light that is in the red end of the spectrum. It is the oldest wavelength

Answer 5

By the wavelength of light you are veiwing.