Jeans Length Using Speed of Sound
The Jeans length is the critical radius for instability of a collapsing thermalized cloud of selfgravitating gas.
The Jeans length is proportional to the sound speed times the square root of the reciprocal of the mass density.
Formula
![Copy to Clipboard QuantityVariable[Subscript["R", "J"], "Length"] == Sqrt[Pi]*QuantityVariable["c", "SoundSpeed"]*Sqrt[Quantity[1, "GravitationalConstant"^(-1)]/QuantityVariable["ρ", "MassDensity"]]](https://www.wolframcloud.com/objects/resourcesystem/marketplacestorage/resources/fe7/fe71c210-15e0-4668-b15b-2ae6b04e3c50/Webpage/FormulaImage.png)
| symbol | description | physical quantity |
|---|---|---|
| RJ | Jeans length | "Length" |
| c | sound speed | "SoundSpeed" |
| ρ | mass density | "MassDensity" |
Forms
Examples
Get the resource:
| In[1]:= |
| Out[1]= | ![]() |
Get the formula:
| In[2]:= |
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Use some values:
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| Out[3]= |


![FormulaData[
ResourceObject[
"Jeans Length Using Speed of Sound"], {QuantityVariable[
"c","SoundSpeed"] -> Quantity[3129.28`6., ("Meters")/("Seconds")],
QuantityVariable[
\!\(\*SubscriptBox[\("R"\), \("J"\)]\),"Length"] ->
Quantity[2.624`4.*^14, "Kilometers"]}]](images/fe7/fe71c210-15e0-4668-b15b-2ae6b04e3c50-io-3-i.en.gif)