<p>It stands for the speed of light (<span class="math-container">$c$</span>) times the redshift (<span class="math-container">$z$</span>) as measured from the redshift of the spectrum.
It is equal to the line-of-sight velocity that the star has. Positive means going away from us.
It is given in a heliocentric reference frame, that is corrected for the rotation of the Earth around its axis/the Sun. </p>

<p>The -2.33 is the velocity (km/s) and the [2.96] is its uncertainty.</p>

CC BY-SA 4.0
2019-06-23T15:47:17.777Z
$cz$ is the line of sight velocity, **if** $z \ll 1$.
ProfRob
CC BY-SA 4.0
2019-06-24T09:27:49.243Z
Normally it holds for individual stars. See comment above for cosmological scale.
Alchimista
CC BY-SA 4.0
2019-06-23T13:40:10.940Z
2019-06-23T13:40:10.940Z
Ewoud
<p>Take DS Geminorum for example, it has a cz of -2.33 [2.96]</p>

<p>My question is what does cz mean, what does is represent? and what does the value in the brackets mean?</p>

<p><a href="http://simbad.u-strasbg.fr/simbad/sim-id?Ident=ds%20gem" rel="nofollow noreferrer">http://simbad.u-strasbg.fr/simbad/sim-id?Ident=ds%20gem</a></p>

<star>
What does cz mean?
MiscellaneousUser
# What does cz mean?

(Asked by: username_0 on 2019-06-23)

Take DS Geminorum for example, it has a cz of -2.33 [2.96]

My question is what does cz mean, what does is represent? and what does the value in the brackets mean?

<http://simbad.u-strasbg.fr/simbad/sim-id?Ident=ds%20gem>

**Tags:** star


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## 1 answers

### Answer by username_1 on 2019-06-23. Score: 4 | Accepted answer

It stands for the speed of light ($c$) times the redshift ($z$) as measured from the redshift of the spectrum.
It is equal to the line-of-sight velocity that the star has. Positive means going away from us.
It is given in a heliocentric reference frame, that is corrected for the rotation of the Earth around its axis/the Sun.

The -2.33 is the velocity (km/s) and the [2.96] is its uncertainty.

> **Comments:**
> **username_2**: $cz$ is the line of sight velocity, **if** $z \ll 1$.  
> **username_3**: Normally it holds for individual stars. See comment above for cosmological scale.  

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