Doppler Shift Light from another galaxy

In summary, we are trying to determine whether a distant galaxy is moving towards or away from us by analyzing the absorption line in its light. To calculate the velocity of the galaxy, we can use the Doppler equations, but if the velocity is a significant fraction of the speed of light, we should use the Relativistic Doppler Shift equation. This equation can be rearranged to calculate the velocity in terms of the wavelengths of the absorption line in the galaxy and the sun.
  • #1
Airman
23
0
When we analyze the light coming from a distant galaxy, we find a particular absorption line with a wavelength of 1118 nm. This same absorption line in light from the sun has a wavelength of 625 nm is this galaxy moving towards us or away from us?

Calculate the magnitude of the velocity of the galaxy relative to us.

I've tried all what I think are the Doppler equations for light, but can't seem to get the right answer.

When I plug in the values to λr = λc/(c − vr), I get 1.32198284 * 10^8 m / s, which the online homework says is wrong.
 
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  • #2
Bave you tried:
943dbf9e018e8e8c13924c01aea4749d.png

and
973e46afbcc9cd3f3177192b613dab14.png
?
 
  • #3
If the classical approach (as you have used) returns a value for the velocity that is a significant fraction of the speed of light (in your case about 44% of c), then you'll want to employ the Relativistic Doppler Shift instead.

λ_s/λ_r = sqrt((1 + beta)/(1 - beta))

where: beta = v/c

This can be rearranged as:

v/c = (λ_s2 - λ_r2)/(λ_s2 + λ_r2)
 

What is Doppler Shift Light from another galaxy?

Doppler shift light from another galaxy is a phenomenon where the light emitted from galaxies outside of our own appears to be shifted in wavelength due to the relative motion between the two galaxies. This is caused by the Doppler effect, which is the change in frequency or wavelength of a wave due to the motion of the source or observer.

How is Doppler Shift Light from another galaxy observed?

Doppler shift light from another galaxy is observed through spectroscopy, which involves analyzing the wavelengths of light emitted from objects. By comparing the observed wavelengths to the expected wavelengths, scientists can determine the amount of Doppler shift and the relative motion between the two galaxies.

What can Doppler Shift Light from another galaxy tell us about the universe?

Studying Doppler shift light from another galaxy can provide valuable information about the expansion and structure of the universe. By analyzing the redshift or blueshift of the light, scientists can determine the distance and speed of galaxies, as well as the distribution of matter in the universe.

What causes Doppler Shift Light from another galaxy?

Doppler shift light from another galaxy is caused by the relative motion between the two galaxies. If a galaxy is moving towards us, the light will appear blueshifted, meaning the wavelengths will be shorter. If a galaxy is moving away from us, the light will appear redshifted, meaning the wavelengths will be longer.

Can Doppler Shift Light from another galaxy be used to study objects within the galaxy?

Yes, Doppler shift light from another galaxy can also be used to study objects within the galaxy, such as stars and planets. By analyzing the Doppler shift of their light, scientists can determine their velocity and motion, as well as any potential gravitational interactions with other objects within the galaxy.

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