<p>The <a href="https://vizier.u-strasbg.fr/viz-bin/VizieR-3?-source=I/350/gaiaedr3" rel="nofollow noreferrer">Gaia EDR3</a> catalogue gives a parallax of <span class="math-container">$10.965 \pm 0.028$</span> milli-arcseconds.</p>
<p>This differs from the DR2 parallax by 0.115 milli-arcseconds. This is not unexpected because there are systematic errors of order 0.1 milli-arcsec in the DR2 parallaxes.</p>
<p>The new EDR3 parallax is expected to have systematic errors that are no bigger than the statistical error bar quoted. The error is small enough that the parallax can be inverted to give a distance of <span class="math-container">$91.20 \pm 0.23$</span> pc (or if you prefer <span class="math-container">$297.5 \pm 0.8$</span> light years).</p>

CC BY-SA 4.0
2021-07-18T07:27:05.027Z
2021-07-18T07:27:05.027Z
ProfRob
<p><a href="http://simbad.u-strasbg.fr/simbad/sim-id?Ident=HD+116798" rel="nofollow noreferrer">SIMBAD</a> lists a Gaia DR2 parallax of 10.85&plusmn;0.03 milli-arcseconds for that star.
Without going into the biases and uncertainties in current Gaia parallax data,
<span class="math-container">$$r \approx \frac{1}{\varpi}$$</span>
where <span class="math-container">$\varpi$</span> is the <a href="https://en.wikipedia.org/wiki/Stellar_parallax" rel="nofollow noreferrer">parallax</a> in arcseconds and <span class="math-container">$r$</span> is the distance in <a href="https://en.wikipedia.org/wiki/Parsec" rel="nofollow noreferrer">parsecs</a>.
This works out to a distance of roughly 92 parsecs or 300 light-years.</p>

CC BY-SA 4.0
2019-05-20T13:29:57.473Z
Where can I read from SIMBAD distance that you quoted?
Fil
CC BY-SA 4.0
2019-05-21T23:33:43.027Z
Actually, the SIMBAD page *does* show the distance: scroll down to "Collections of Measurements" and select "display all measurements". It gives the distance as 92.1353±0.2377 pc.
Chappo Hasn't Forgotten
CC BY-SA 4.0
2019-05-22T10:26:40.877Z
Your error bar does not take account of the published systematic uncertainty in the Gaia parallax zero-point. An additional 0.1 mas of error is warranted at present.
ProfRob
CC BY-SA 4.0
2019-05-20T13:23:15.503Z
2019-05-22T16:10:02.687Z
2019-05-22T16:10:02.687Z
Mike G
<p>Mizar and Alcor, each about 83 light-years away (in fact Mizar presents system of four stars and Alcor is binary system. It is not yet known if those 6 stars presents one or two star systems. In further years, data provided by GAIA space telescope will show us if there is one or two systems), have a fainter line-of-sight companion known as
<a href="https://en.wikipedia.org/wiki/Sidus_Ludoviciana" rel="nofollow noreferrer">Ludwig's star</a>, which was mistaken for a planet in 1722.
The Wikipedia page only says it is "roughly five times more distant," citing <a href="http://www.leosondra.cz/en/mizar/" rel="nofollow noreferrer">A New View of Mizar</a> by Leos Ondra.
Is a better distance estimate available?</p>

<star><distances>
Ludwig's star distance
Fil
# Ludwig's star distance

(Asked by: username_0 on 2019-05-20)

Mizar and Alcor, each about 83 light-years away (in fact Mizar presents system of four stars and Alcor is binary system. It is not yet known if those 6 stars presents one or two star systems. In further years, data provided by GAIA space telescope will show us if there is one or two systems), have a fainter line-of-sight companion known as
[Ludwig's star](https://en.wikipedia.org/wiki/Sidus_Ludoviciana), which was mistaken for a planet in 1722.
The Wikipedia page only says it is "roughly five times more distant," citing [A New View of Mizar](http://www.leosondra.cz/en/mizar/) by Leos Ondra.
Is a better distance estimate available?

**Tags:** star, distances

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## 2 answers

### Answer by username_2 on 2019-05-20. Score: 7 | Accepted answer

[SIMBAD](http://simbad.u-strasbg.fr/simbad/sim-id?Ident=HD+116798) lists a Gaia DR2 parallax of 10.85±0.03 milli-arcseconds for that star.
Without going into the biases and uncertainties in current Gaia parallax data,
$$r \approx \frac{1}{\varpi}$$
where $\varpi$ is the [parallax](https://en.wikipedia.org/wiki/Stellar_parallax) in arcseconds and $r$ is the distance in [parsecs](https://en.wikipedia.org/wiki/Parsec).
This works out to a distance of roughly 92 parsecs or 300 light-years.

> **Comments:**
> **username_0**: Where can I read from SIMBAD distance that you quoted?  
> **username_3**: Actually, the SIMBAD page *does* show the distance: scroll down to "Collections of Measurements" and select "display all measurements". It gives the distance as 92.1353±0.2377 pc.  
> **username_1**: Your error bar does not take account of the published systematic uncertainty in the Gaia parallax zero-point. An additional 0.1 mas of error is warranted at present.  

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### Answer by username_1 on 2021-07-18. Score: 2

The [Gaia EDR3](https://vizier.u-strasbg.fr/viz-bin/VizieR-3?-source=I/350/gaiaedr3) catalogue gives a parallax of $10.965 \pm 0.028$ milli-arcseconds.

This differs from the DR2 parallax by 0.115 milli-arcseconds. This is not unexpected because there are systematic errors of order 0.1 milli-arcsec in the DR2 parallaxes.

The new EDR3 parallax is expected to have systematic errors that are no bigger than the statistical error bar quoted. The error is small enough that the parallax can be inverted to give a distance of $91.20 \pm 0.23$ pc (or if you prefer $297.5 \pm 0.8$ light years).


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