Re: Gravitational red-shifting in the biggest star. What are the real colors?

Paul.B.Andersen <relativity@paulba.no> wrote:

Den 28.09.2024 04:34, skrev rhertz:

This link illustrates a bit:
 
https://en.wikipedia.org/wiki/Gravitational_redshift
 
Using the most common formula from that link: "To first approximation,
gravitational redshift is proportional to the difference in
gravitational potential divided by the speed of light squared"
 
?f/f = ??/? = z = GM/c? (1/R - 1/r) = ?(R)/c? - ?(r)/c?

 
  ??/? = GM/Rc?  observed at infinity  (r -> ∞)
 
https://www.space.com/41290-biggest-star.html

 
G = 6.6743E?11 m^3 kg^?1 s^?2
M = 5E+09 x 1.989E+30 Kg = 9.945E+39 Kg
R = 1,700 x 634,000 Km = 1,077,800,000,000 m
 
 
?(R)/c? = 6,842,736.59

 
 From whence did you get the idiotic idea that the mass
of UY Scuti was 5 billion solar masses? :-D
 
M = 30 solar masses =  5.967e31 kg
R = 696340e3?1700 m = 57868e6 m
c = 299792458 m/s
 
??/? = GM/Rc? = 7.65e-7
 
Which is less than the red shift from the Sun.
 

 
In comparison, ?(RSun)/c? = 0.000002327

 
M = 1.989E+30 kg
R = 696340e3 m
 
??/? = GM/Rc? = 2.12e-6
 
 
 

 
WHAT IS WRONG WITH MY CALCULATIONS, BASED ON THE WIKI LINK?

 
Now you know.

He is looking for trouble where none exists.
Even for neutron stars you get a nice finite gravitational redshift,
which is 'easily' observable. For example:
<https://pubmed.ncbi.nlm.nih.gov/12422210/>

They find a redshift value of z = 0.35 ,
which is consistent with standard neutron star models,
(but not with some exotic ones)

Jan

(such a large gravitational redshift dwarfs any possible Doppler shift)