When calculating the red shift of a star, what does the value mean?

Question

Is red shift (z) given as a velocity, or a constant? If it's a constant, what does the given value mean?

Have you looked on the Wikipedia entry on redshift? – Kyle Kanos Aug 31 '17 at 10:00 — Kyle Kanos, Aug 31 '17 at 10:00

score 2 · Answer 1 · answered Aug 30 '17 at 12:36

2

Red shift does not have units so it is not a velocity, but can be converted to one using the equation $v = zc$. Instead, redshift is given as the "error" in the wavelength.

$$\frac{\lambda_{measured} - \lambda_{expected}}{\lambda_{measured}}=z$$

This can change but with no units you can consider redshift/blueshift a constant.

answered Aug 30 '17 at 12:36

thesecretmaster

121

2

Note that the equation $v = zc$ is only valid for small (non-relativistic) velocities. – pela Aug 30 '17 at 12:50

When calculating the red shift of a star, what does the value mean?

1 Answers1