All Questions
Tagged with redshift doppler-effect
13
questions
2
votes
1
answer
96
views
How does doppler shift work for distant stars [duplicate]
I dont understand how you can look at the light from a star and say that it has been doppler shifted. For example a star emits a photon in the wavelength of 500nm and by the time it reaches earth it ...
- 125
3
votes
1
answer
131
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Radial velocity stability to spectrum shift calculation
I am engineer new to Astronomy and am trying to understand spec of an spectrograph (RV stability = 2m/s). There is a note in document saying "RV shift of 2 m/s is equivalent to a shift of the ...
- 33
3
votes
1
answer
239
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Why is cosmological redshift treated as a different phenomenon to doppler redshift? [duplicate]
I understand that the expansion of the universe causes unbound structures to move apart from each other. This means that unbound structures have negative relative momentum due to universal expansion.
...
- 211
2
votes
1
answer
153
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Is there any way to distinguish the doppler redshift from a distant galaxy from the probably much greater cosmological redshift? [duplicate]
Is there any way to distinguish the doppler redshift from a distant galaxy, caused by its initial recessional velocity relative to this galaxy, from the probably much greater, cosmological redshift, ...
- 223
1
vote
1
answer
221
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Intuitive explanation for why the Doppler effect (and red-shift) happens?
I was looking for an intuitive explanation as to why the Doppler effect happens. I haven't found any, but this is what I thought:
-Waves emitted travel at a constant speed
-The source emits a wave
-If ...
- 201
0
votes
1
answer
75
views
Which redshift is used to determine the Hubbleconstant?
I think they measure cosmological redshift to use in the Law of Hubble-Lemaître together with the distance to calculate $H_0$. Is this correct, or do they use Doppler shift (too)?
$H_0$ indicates how ...
- 402
2
votes
2
answers
674
views
Is there still a red shift when moving perpendicular to the direction of incidence?
This answer suggests that when there is zero radial velocity... there will be no Doppler shift but it's not likely to be intended as precise and absolute.
I remember reading about something like this ...
- 30.7k
2
votes
1
answer
173
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Universe expansion
I'm reading the book "The theory of everything". In the second chapter it says the Universe is expanding, and we know this because the measurements made using the Doppler effect of other ...
- 31
10
votes
3
answers
3k
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Cosmological redshift vs doppler redshift
I'm reading Harrison's "Cosmology: Science of the universe" because Harrison focuses on the distinction between cosmological redshift (he calls it expansion redshift) and the Doppler redshift.
He ...
- 165
1
vote
1
answer
491
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Question about Hubble parameter (Hubble constant) and measuring it
I see this question in "An introduction to modern cosmology - Andrew Liddle - Wiley Publication":
In the real Universe the expansion is not completely uniform. Rather,
galaxies exhibit some ...
- 483
4
votes
2
answers
3k
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Gravitational red shift vs Doppler redshift: Is the universe really expanding?
Is it possible that the redshift observed by Edwin Hubble is really from a gravitational redshift and the universe isn't expanding as he has predicted?
What I think I know thus far is this:
Redshift ...
- 479
4
votes
2
answers
291
views
How to disentangle a very distant star's relative velocity vs. redshift distance
We measure a star's relative velocity towards or away from us via its Doppler-shifted spectrum. This is also how we measure the distance of very distant stars: measuring the shifts in the spectrum ...
- 652
3
votes
1
answer
3k
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How do we know that light is redshifted/blueshifted and not the original light of a star/galaxy? [duplicate]
If a star/galaxy is moving towards us, then its light is blueshifted, and if it is moving away from us, then its light is redshifted. How do we exactly know that the color we are seeing is not part of ...
- 147