<p>Is there a way to take the red shift of an object and, from that, calculate a rough estimate of its distance from us (in parsecs, preferably)?</p>

CC BY-SA 4.0
2018-05-25T19:02:45.777Z
Look up Hubble's Law.
Phiteros
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2018-05-25T19:14:49.930Z
@Phiteros Oh, I see. $v = cz$ and $v = H_0 d$, so $d = \frac{cz}{H_0}$. I didn't scroll far enough down Wikipedia to see $v=cz$ :/
Beta Decay
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2018-05-25T19:15:44.223Z
Keep in mind that that's just an approximation; you have to go through a lot more complicated differential equations for high redshifts.
Phiteros
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2018-05-25T19:16:45.817Z
@Phiteros Yes, that's fine. I don't need anything accurate
Beta Decay
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2018-05-25T21:09:29.910Z
Just to clarify, at high redshifts it's not only inaccurate, it's completely wrong. For $z\lesssim 0.1$ it's fine, at $z=3$ you'll overestimate the distance by a factor of two, at $z=10$ by a factor of five, and at $z=1100$ by a factor of 350.
pela
CC BY-SA 4.0
2018-05-26T13:29:10.580Z
Use online calculator such as this: http://www.astro.ucla.edu/~wright/CosmoCalc.html
Kornpob Bhirombhakdi
CC BY-SA 4.0
2018-05-26T13:36:08.537Z
@Phiteros Out of curiosity, what is the differential equation that I'd have to solve?
Beta Decay
CC BY-SA 4.0
2018-05-26T18:22:31.463Z
https://en.wikipedia.org/wiki/Hubble%27s_law#Derivation_of_the_Hubble_parameter
Phiteros
<distances><redshift><astrometry>
How can you estimate distance of an object by its redshift?
Beta Decay
# How can you estimate distance of an object by its redshift?

(Asked by: username_0 on 2018-05-25)

Is there a way to take the red shift of an object and, from that, calculate a rough estimate of its distance from us (in parsecs, preferably)?

**Tags:** distances, redshift, astrometry

> **Comments:**
> **username_1**: Look up Hubble's Law.  
> **username_0**: @username_1 Oh, I see. $v = cz$ and $v = H_0 d$, so $d = \frac{cz}{H_0}$. I didn't scroll far enough down Wikipedia to see $v=cz$ :/  
> **username_1**: Keep in mind that that's just an approximation; you have to go through a lot more complicated differential equations for high redshifts.  
> **username_0**: @username_1 Yes, that's fine. I don't need anything accurate  
> **username_2**: Just to clarify, at high redshifts it's not only inaccurate, it's completely wrong. For $z\lesssim 0.1$ it's fine, at $z=3$ you'll overestimate the distance by a factor of two, at $z=10$ by a factor of five, and at $z=1100$ by a factor of 350.  
> **username_3**: Use online calculator such as this: http://www.astro.ucla.edu/~wright/CosmoCalc.html  
> **username_0**: @username_1 Out of curiosity, what is the differential equation that I'd have to solve?  
> **username_1**: https://en.wikipedia.org/wiki/Hubble%27s_law#Derivation_of_the_Hubble_parameter  

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## 0 answers

