<p>While <a href="https://astronomy.stackexchange.com/questions/2092/what-is-the-minimum-mass-required-so-that-objects-become-spherical-due-to-its-ow">these posts</a> (attempt to) answer what the minimum mass is to <em>be able to</em> achieve an ellipsoidal shape, my question asks for the mass at which a body <em>definitely</em> collapses into an ellipsoid. Meaning, from <em>this</em> mass on a body definitely won't be irregular nor borderline but clearly an ellipsoid due to hydrostatic equilibrium. The value will be different for ice dwarfs (like Enceladus and Pluto), terrestrial bodies (like the inner four planets, the Moon and Io) and gas giants. I'm curious on the mass for each of them, I guess in 2021 science has progressed enough to provide an approximate answer.</p>
<p>The largest and most massive object I know of whose sphericity is questionable is Haumea in the Kuiper belt at 0.00066 Earth masses (~ 1/3 Pluto's) and an equatorial diameter at 2322 km (1443 mi).</p>

CC BY-SA 4.0
2021-01-02T01:20:37.483Z
I suppose you have taken a look at https://en.wikipedia.org/wiki/Hydrostatic_equilibrium ?
Pierre Paquette
CC BY-SA 4.0
2021-01-02T07:15:15.513Z
@PierrePaquette Of course. It's a pity that Wikipedia doesn't have an article dealing with the hydrostatic equilibrium of celestial bodies only, something like "Hydrostatic equilibrium in planetary geology". However, I mean to recall to once have sighted there somewhere that it's questionable whether even Saturn is in equilibrium but I couldn't find it anymore (obviously due to the supposed lack of a solid/liquid core of Saturn).
Greenhorn
<gravity><mass><hydrostatic-equilibrium>
What is the mass for a celestial body to definitely achieve hydrostatic equilibrium?
Greenhorn
# What is the mass for a celestial body to definitely achieve hydrostatic equilibrium?

(Asked by: username_0 on 2021-01-01)

While [these posts](https://astronomy.stackexchange.com/questions/2092/what-is-the-minimum-mass-required-so-that-objects-become-spherical-due-to-its-ow) (attempt to) answer what the minimum mass is to *be able to* achieve an ellipsoidal shape, my question asks for the mass at which a body *definitely* collapses into an ellipsoid. Meaning, from *this* mass on a body definitely won't be irregular nor borderline but clearly an ellipsoid due to hydrostatic equilibrium. The value will be different for ice dwarfs (like Enceladus and Pluto), terrestrial bodies (like the inner four planets, the Moon and Io) and gas giants. I'm curious on the mass for each of them, I guess in 2021 science has progressed enough to provide an approximate answer.

The largest and most massive object I know of whose sphericity is questionable is Haumea in the Kuiper belt at 0.00066 Earth masses (~ 1/3 Pluto's) and an equatorial diameter at 2322 km (1443 mi).

**Tags:** gravity, mass, hydrostatic-equilibrium

> **Comments:**
> **username_1**: I suppose you have taken a look at https://en.wikipedia.org/wiki/Hydrostatic_equilibrium ?  
> **username_0**: @username_1 Of course. It's a pity that Wikipedia doesn't have an article dealing with the hydrostatic equilibrium of celestial bodies only, something like "Hydrostatic equilibrium in planetary geology". However, I mean to recall to once have sighted there somewhere that it's questionable whether even Saturn is in equilibrium but I couldn't find it anymore (obviously due to the supposed lack of a solid/liquid core of Saturn).  

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## 0 answers

