<p>A <a href="https://science.sciencemag.org/content/364/6437/272.abstract" rel="nofollow noreferrer">science paper</a> from 2019 by K. Kitazato <em>et al.</em> shows a shape model of the surface in Fig. 2, so  we now indeed know the exact size and  the exact mass, even the surface temperature distribution:</p>
<p><a href="https://i.sstatic.net/fVaEU.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/fVaEU.png" alt="Shape Model of 162173 Ryugu." /></a></p>
<p>The quoted paper refers to <a href="https://science.sciencemag.org/content/364/6437/268" rel="nofollow noreferrer">S. Watanabe et al., Science, 2019</a> which has all the details</p>
<blockquote>
<p>Ryugu has an oblate body, with an <strong>equatorial radius of 502 ± 2 m and polar-to-equatorial axis ratio of 0.872 ± 0.007</strong>. The total volume obtained from the SPC-based shape model is <span class="math-container">$0.377 {\rm km}^3$</span>, with an uncertainty of 1.3%. We conducted a gravity measurement during a spacecraft ballistic descent down to 0.85 km from the asteroid surface and a subsequent ballistic ascent up to 5.4 km. The <strong>estimated mass is <span class="math-container">$4.50\times 10^{11} {\rm kg}$</span></strong>, with an uncertainty of 1.3%, mainly because of uncertainties in the solar radiation pressure on the spacecraft.</p>
</blockquote>
<p>The <strong>highlighting</strong> in the quote is from me.</p>

CC BY-SA 4.0
2021-02-17T08:18:07.590Z
2021-02-17T08:18:07.590Z
B--rian
<p>&quot;Give a man a watch and he will know the time; give him two and he will never be sure&quot; - this was my impression when reading the Wikipedia article on <a href="https://en.wikipedia.org/wiki/162173_Ryugu" rel="nofollow noreferrer">162173 Ryugu</a>.</p>
<blockquote>
<p>Mean diameter:</p>
<ul>
<li>0.865±0.015 km[3]</li>
<li>0.87 km[4]</li>
<li>0.90±0.14 km[5]</li>
<li>0.92±0.12 km[6]</li>
<li>0.980±0.029 km[7]</li>
<li>1.13±0.03 km[8]</li>
</ul>
</blockquote>
<p>And no mass estimates at all.</p>
<p>Now that Hayabusa2 has arrived, do we have solid measurements of Ryugu's size and mass yet?</p>

CC BY-SA 4.0
2018-07-08T13:43:10.493Z
Give JAXA some time to collect and process their data. The [papers about 25143 Itokawa](https://doi.org/10.1126/science.1125841) were published 8 months after the Hayabusa 1 encounter.
Mike G
CC BY-SA 4.0
2018-07-08T14:19:08.573Z
@MikeG: okay, then the question can just wait for the answer to become available.
SF.
CC BY-SA 4.0
2018-07-27T16:21:14.743Z
There is a special session on Hayabusa2 at the Division of Planetary Sciences 50th meeting in October. I would expect the first preliminary science results to be announced there but the data analysis takes time. Volume ans Mass in particular take a while as you have to make sure you've mapped all the surface of the asteroid and sampled the variable gravity field
astrosnapper
<asteroids>
Do we finally have a decent set of parameters of 162173 Ryugu?
SF.
# Do we finally have a decent set of parameters of 162173 Ryugu?

(Asked by: username_0 on 2018-07-08)

"Give a man a watch and he will know the time; give him two and he will never be sure" - this was my impression when reading the Wikipedia article on [162173 Ryugu](https://en.wikipedia.org/wiki/162173_Ryugu).

> Mean diameter:
>
> * 0.865±0.015 km[3]
> * 0.87 km[4]
> * 0.90±0.14 km[5]
> * 0.92±0.12 km[6]
> * 0.980±0.029 km[7]
> * 1.13±0.03 km[8]

And no mass estimates at all.

Now that Hayabusa2 has arrived, do we have solid measurements of Ryugu's size and mass yet?

**Tags:** asteroids

> **Comments:**
> **username_1**: Give JAXA some time to collect and process their data. The [papers about 25143 Itokawa](https://doi.org/10.1126/science.1125841) were published 8 months after the Hayabusa 1 encounter.  
> **username_0**: @MikeG: okay, then the question can just wait for the answer to become available.  
> **username_2**: There is a special session on Hayabusa2 at the Division of Planetary Sciences 50th meeting in October. I would expect the first preliminary science results to be announced there but the data analysis takes time. Volume ans Mass in particular take a while as you have to make sure you've mapped all the surface of the asteroid and sampled the variable gravity field  

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## 1 answers

### Answer by username_3 on 2021-02-17. Score: 3 | Accepted answer

A [science paper](https://science.sciencemag.org/content/364/6437/272.abstract) from 2019 by K. Kitazato *et al.* shows a shape model of the surface in Fig. 2, so we now indeed know the exact size and the exact mass, even the surface temperature distribution:

[![Shape Model of 162173 Ryugu.](https://i.sstatic.net/fVaEU.png)](https://i.sstatic.net/fVaEU.png)

The quoted paper refers to [S. Watanabe et al., Science, 2019](https://science.sciencemag.org/content/364/6437/268) which has all the details

> Ryugu has an oblate body, with an **equatorial radius of 502 ± 2 m and polar-to-equatorial axis ratio of 0.872 ± 0.007**. The total volume obtained from the SPC-based shape model is $0.377 {\rm km}^3$, with an uncertainty of 1.3%. We conducted a gravity measurement during a spacecraft ballistic descent down to 0.85 km from the asteroid surface and a subsequent ballistic ascent up to 5.4 km. The **estimated mass is $4.50\times 10^{11} {\rm kg}$**, with an uncertainty of 1.3%, mainly because of uncertainties in the solar radiation pressure on the spacecraft.

The **highlighting** in the quote is from me.


---

