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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Is the difference of redshift parameter z able to prove expansion is accelerating in flat FLRW universe model?
Sorry for my bad english, this is not my mother tongue.
Recently, I've encountered a problem in cosmology class that is about FLRW universe.
Assuming that the universe we inhabit is composed of non-...
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JWST Early Black Holes: Gas Collapsed To Metallic Hydrogen Core?
I was reading an article about early black holes found by JWST at Redshift 9. And saw that there was wonder at how large amounts of gas could collapse into a black hole as a theory.
So my question is ...
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Finding an expression for the rate of change of Comoving volume with respect to redshift
I am trying to find the expression for the rate of change of comoving volume with respect to redshift, that is $\frac{\mathrm{d}V_c}{\mathrm{d}z}$. In this paper (Hogg, David W.), the comoving volume ...
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The "k-effect"?
I'm reading some older materials which refer to something called the "k-effect". This was described as "hot stars in the Sun’s neighborhood are moving away from us in all directions, ...
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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 ...
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Why does the velocity dispersion within a galaxy cluster decrease as a function of radius?
In the paper 10.1093/mnras/sty2379, there are plots showing the velocity dispersion as a function of radius.
Focusing on the right-hand plot, non-merging normal clusters, intuitively why should the ...
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Could we (Earth, Humanity, Solar System) be falling into a black hole?
With the expansion of the universe, all objects far away from us appear to be moving away (ie: exhibit Redshift). With distance, this acceleration / redshift also seems to increase (~73,000 (m/s) / (...
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If astronomers didn't know about redshift could we still determine the universe is expanding?
What other evidence is there for the expansion of the universe?
Would the equations of physics look wrong without it?
user51209
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Can the cosmological constant be coupled to redshift of radiation
Can space-time be more embedded with the things inside it than we actually think?Can the redshift of radiation be a property of spacetime and that dark energy exists only to conserve the overall ...
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Is Webb or any near-future telescopes like ELT capable of observing redshift changes to confirm General Relativity?
The (Davis and Lineweaver (2003)) "Expanding Confusion" paper states that "the expected change in redshift due to cosmological acceleration or deceleration is only ∆z ∼ 10^(−8) over 100 ...
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If a supernova explodes close to the centre of the milky way does its light get blueshifted by dark matter by the time it reaches the Earth?
Does the dark matter halo of the milky way cause most of the change in wavelength or is baryonic matter responsible?
user50918
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How can we estimate distance of galaxies by only redshift when there are other several factors other than distance to cause redshift
There are different factors for red appearance of different objects in the night sky. Two reasons which I know are
Star red by nature
Example: red supergiants
They emit red light because of their ...
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How can redshifted light be detected?
I've been reading about redshifts and it got me really curious. Basically, I want to figure out how we know light is redshifted and what's the original emitted light.
I found the following question ...
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Could the redshift of all incoming photons be explained by a massive ring of distant masses pulling the sources of the photons away?
ChatGPT and wikipedia have informed me that the primary evidence for the theory that the universe is expanding is the fact that photons that arrive to our planet from all directions are being ...
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Does a photon travelling inside a gravitational wave get stretched and compressed or redshifted? [closed]
The photon would be travelling at the same speed as the gravitational wave.
user50623
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How far away must galaxies be before current telescopes can no longer measure how quickly they are rotating around one another or internally?
What is the distance limit and does it depend on the size of the galaxy and on noise and interference from gas clouds and our own Milky Way?
user50623
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Can the expansion of the universe cool my beer?
So the expansion of the universe stretches the light traveling through the void, as demonstrated by the cosmic microwave background radiation. These photons are lower energy than when they are ...
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Interpreting the color of galaxies in deep field images
The HST produced some deep field images in mostly visible light, which contain thousands of galaxies that range in color from white to red (e.g. see here). I understand that the interpretation of ...
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Empirical Constraints on the Time Evolution of Cosmological Redshifts
The standard model of Cosmology predicts that the redshift of a single source at fixed comoving distance varies with observation time according to
$$ \dot z = \left( 1+z - \frac{H(z)}{H_0} \right) H_0....
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How does one estimate the mass of a galaxy using the Balmer break region?
I am currently reading the recent astrophysical paper "A population of red massive galaxies ~600Myr after the Big Bang'.
In the first paragraph/abstract it mentions, "It has been difficult ...
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How does the Sachs-Wolfe effect confirm the existence of dark energy?
How is the Sachs–Wolfe effect and the existence of voids significant in providing physical evidence for dark energy?
user48394
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3d distance between the Galaxies inside the galaxy cluster
I am currently working on the dynamics of the galaxy cluster, so i am trying to get the distance between the galaxies inside the galaxy cluster from its centre. As a input i have RA , DEC and Z (...
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What accounts for a Lyman-break for all wavelengths shorter than 91.2nm if the Lyman limit is the highest energy photon that neutral hydrogen absorbs?
From this description of Lyman-break galaxies, I don't understand how:
...radiation at higher energies than the Lyman limit at 912 Å is almost completely absorbed by neutral gas around star-forming ...
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How do we know universe is expanding and not light slowing down? [duplicate]
We tend to take some things for granted, for example the light of speed is constant, but what if it isn't? How can we know that light is not slowing down at great distances for example, or that light ...
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Redshift distance proportionality at high Z and need for "mighty mouse" galaxies?
Allegedly supported by some evidence from the new James Webb space telescope physicist Eric Lerner has written an article that have garnered some attention. He writes that:
"Put another way, the ...
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What parameters of the Big Bang model will have to be adjusted to account for JWST's observations of highly redshifted galaxies?
There are a lot of claims, on YouTube at least, that the James Webb space telescope have found too many to old/highly redshifted normal looking galaxies to fit easily into the Big Bang model.
One such ...
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Minimum redshift for galaxies receding $\geq c$ when light transmitted
What is the minimum redshift for galaxies receding $\geq c$ when light was first transmitted that are visible today from Earth? Is that value the same as maximum angular size distance?
This question ...
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How is z calculated in red shift observations?
If z is calculated using the ratio between observable wavelength and emitted wavelength, how do we know the emitted wavelength of a star that is moving away from us? Wouldn’t we have to be at a ...
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redshift puzzle
I have the central line of the spectrum of an elliptical galaxy (NGC:4697) and a template K-star. I have calculated the redshift z by computing the crosscorrelation function between the galaxy and the ...
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Plotting galaxies in 3-D
Suppose I have a catalogue of galaxies in a .dat file with each row representing information about a galaxy: right ascension of the galaxy, declination of the ...
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How does SDSS estimate photometric redshift of sources?
I'm looking through the data in SDSS DR 12:
...
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Why is the CMB's redshift so high?
It is pretty well-established that the CMB was originally emitted around 380,000 years after the Big Bang, at a redshift of ~1100.
The most distant known object is HD1, the light from which was ...
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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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Classifying 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 the SNe dataset "Pantheon", I find there are two redshifts:...
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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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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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