What causes variations in redshift measurements?

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Discussion Overview

The discussion revolves around the variations in redshift measurements of receding galaxies, specifically addressing the discrepancies that arise when measuring redshift from different spectral peaks. The scope includes conceptual understanding and technical reasoning related to astronomical measurements.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • The original poster questions why different spectral peaks yield varying redshift values, suggesting that the method of measurement might be influencing the results.
  • Some participants inquire whether all spectral peaks shift by the same number of nanometers, indicating a potential area of confusion regarding the uniformity of shifts.
  • Another participant asserts that the shifts are proportional to wavelength, implying a relationship that could explain the observed discrepancies.

Areas of Agreement / Disagreement

The discussion reflects uncertainty, with participants exploring different aspects of redshift measurements without reaching a consensus on the implications of their observations.

Contextual Notes

The discussion does not resolve the assumptions regarding the uniformity of spectral shifts or the implications of using different peaks for redshift calculations.

Walternate
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Hello!
I have a small question, in my textbook and everywhere I look online it states that to find the redshift of a receding galaxy from the spectrograph you divide the change in wavelength by the original point you are measuring from.
The problem I have is, if there is a 20nm shift for example across the whole graph then you get different results depending on which peaks you decide to take the measure from.
For instance if you had 420nm > 440nm the redshift would be 0.047 3.d.p but if you used another peak at 620nm shifting to 640nm you would get a redshift of 0.032 3.d.p
Completely different figures that would alter any future calculations such as recession speed but for the same redshift.

I'm sure that as usual I'm missing something obvious, but after much searching I can still not work out what it is.. Can anyone help please? Thanks!
 
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Do all peaks shift the same number of nm?
 
The shifts are proportional to wavelength.
 
Exactly. Unfortunately, it seems that we are too late, as the original poster was last logged in less than an hour after the original post.
 

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