# Questions tagged [redshift]

Questions related to the phenomenon whereby electromagnetic radiation (such as visible light) generated by an object moving away from an observer will have increase in wavelength (i.e. shifted toward the red end of the spectrum) once it reaches the observer.

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### Angle to the line of sight

I don't understand this angle used in galaxy clustering. There is the line of sight and this angle to the line of sight which is not clear to me. Here is a transcript of a description from 1705.05442: ...
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### How are CMB frame redshifts of galaxies corrected for coherent flows?

Say, if I downloaded the CMB frame redshifts of some galaxies from NED database, then what is the procedure to correct it for coherent flows? I'm using the SNooPy(snpy) Python package to analyze some ...
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### Stellar connectivity for different cosmological redshifts

I'm creating models of stellar connectivity, for a range of cosmological redshifts (z=9, z=7, z=5, z=3, z=1, z=0, z=0.5). For that I'm doing the following steps: Sampling simulation sub-halos for ...
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### How far away from us was Earendel star when it emitted the light that is just now reaching us?

From what I've read, the look back time is about 12.9 billion light years, and the current distance to the Earendel star is approximately 28 billion light years... How close to us was it when it ...
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### Declaring of 3C273 as a quasi-stellar object

I am currently reading A Brief History of Time and chapter 6 about black holes. Now, here it says He found it too large to be caused by a gravitational field: if it had been a gravitational redshift, ...
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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 ...
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### Is luminosity distance related to both heliocentric redshift and CMB restframe redshift？

The luminosity distance $d_l=(1+z)r(z)$, where $r(z)$ is given by $r(z)=cH^{-1}_0\int_{0}^{z}\frac{dz'}{E(z')}$. When I use SN dataset Pantheon, I find there are two redshift $z_{cmb}$ and $z_{hel}$. ...
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### Is there physical evidence to distinguish between the expansion of space and an anthropocentric universe?

When we look in all directions, we see distant objects red-shifted, with the size of the red-shift correlated with the distance from us. As I understand it, the consensus among cosmologists is that ...
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### How did Hubble know the red shift difference between "moving away" and "old"?

My 9yo daughter is very into space at the moment and asked a question that my physics knowledge (6th form college, 20 years ago) is way too poor to answer. Her space book tells us that as stars age, ...
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### Doppler Redshift vs. Cosmological Redshift ... or Both?

There are several existing threads on the difference between cosmological and Doppler redshifts. However, I don't see that any of them answered the question below. @pela gave the following example: &...
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### Intergalactic Lyman-alpha absorption for high redshift quasars (Gunn-Peterson effect)

This is a follow up to a recent question on SE asking about the apparent suppression of radiation shortward of the (red-shifted) Ly-$\alpha$ line of a quasar at redshift $z=6.53$. The general ...
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1 vote
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### Calculate speed of a galaxy with redshift

I was going through some old exercises but I could never figure out who to solve this one The hydrogen absorption line (656 nm) of the galaxy NGC 77 is shifted by 41 nm into the reddish wavelength ...
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### How to interpret this spectrum of the "new DESI Quasar at z = 6.53"; what causes the big edge at about 9150 Angstroms?

I'm not exacty sure why but Scitech Daily's Seeing Dark Energy’s True Colors: DESI Creates Largest 3D Map of the Cosmos includes the graphic and caption below. It indicates a quasar in a Hubble image ...
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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. ...
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### How to calculate radial velocity from redshift? [duplicate]

Ok, I know the question sounds silly, but please hear me out (at the very end it will probably still be silly though, albeit maybe differently). I'm trying to create a visualization of the galactic ...
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### Are gravitational waves red-shifted?

Gravitational waves originate from significant distances. Presumably they are red-shifted the same amount as the galaxies they originated in. In the absence of gravitational “spectral lines”, can this ...
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### Can the gravitational redshift of our sun be measured?

How much of a wavelength change does our sun’s gravity cause in the light it emits? I imagine this could be measured by the shift in its spectral lines. And by extension, does the earth’s ...
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### Could quasars be interior to the event horizon of a SMBH?

My question is prompted by suspicion of three current ideas in astrophysics: GR predicts a singularity at the center of a BH without regard to QM. quasar hyper-luminosity is caused by an acretion ...
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### How to remove redshift from galaxy spectra in Python?

Hello I extracted a spectrum from the central region of the 2D spectrum of the major axis from NGC 4697 (I just took a central row in the 2D data set, see this question for more information: How to ...
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