- #1

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Is there a simple formula/equation for calculating the mass of a star simply by measuring it's redshift. I know there is a way to do it, but have been unable to find any clues on the web..

Thanks for your help! :)

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- Thread starter LachyP
- Start date

- #1

- 38

- 4

Is there a simple formula/equation for calculating the mass of a star simply by measuring it's redshift. I know there is a way to do it, but have been unable to find any clues on the web..

Thanks for your help! :)

- #2

- 16,920

- 6,729

If you know or can neglect the effects of the other contributions, you can use the gravitational red shift to compute the mass of the star (or rather M/R, gravitational redshift depends on this quantity).

- #3

- 38

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- #4

- 16,920

- 6,729

- #5

- 38

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I've been working on it, and I think this may work, M = z(rc^2)/G , where "z" is the redshift, do you think this would work, it seems to be giving around the correct result, but I would much prefer someone wiser to review and correct...

- #6

- 16,920

- 6,729

- #7

- 38

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OK thank you for the help and advice :)

- #8

Ken G

Gold Member

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And note you are actually getting M/r, not M, by observing z. That wouldn't work so well for giant stars, because M/r is very small and hard to detect, and it's not that helpful for main-sequence stars, because they all tend to have a similar M/r so you'd need to detect z very precisely to distinguish them, but the z would only be about 1 part in 100,000. But it is very handy for white dwarfs, because white dwarfs have a mass-radius relationship, such that r is proportional to MI've been working on it, and I think this may work, M = z(rc^2)/G , where "z" is the redshift, do you think this would work, it seems to be giving around the correct result, but I would much prefer someone wiser to review and correct...

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