Difference between redshifts

  • B
  • Thread starter sqljunkey
  • Start date
  • #1
138
7

Main Question or Discussion Point

How can someone tell the difference between a super massive galaxy's redshift and a galaxy that is accelerating away?
 

Answers and Replies

  • #2
Ibix
Science Advisor
Insights Author
6,472
5,173
I don't understand the question - "super massive galaxy" is not a term I'm familiar with, and galaxies aren't typically accelerating.

Do you mean how can we distinguish between gravitational redshift from a super massive black hole and cosmological redshift? Because the gravitational redshift from a black hole at the core of a galaxy would be different across the galaxy, and insignificant beyond a barely noticeable fraction of the core. Cosmological redshift is the same for the entire galaxy.
 
  • Like
Likes Dale
  • #3
PeroK
Science Advisor
Homework Helper
Insights Author
Gold Member
13,506
5,992
How can someone tell the difference between a super massive galaxy's redshift and a galaxy that is accelerating away?
If you detect light you have one parameter: the measured wavelength. Any "redshift" is inferred from other factors, such as that you are observing a shifted hydrogen spectrum. There is, therefore, nothing inherent in the measured wavelength that tells you anything other than the measured wavelength.
 
  • Like
Likes Ibix
  • #4
anuttarasammyak
Gold Member
247
106
Say you observe same amount of red-shift for the two galaxies, observe distances of these galaxies from the Earth. The Shorter distance galaxy has stronger intrinsic gravity attraction, with the expanding universe considered.
 
Top