Can anyone help me by defining what is exactly Bondi Radius? I have searched far and wide but the results are very complicated and so far I have only rough idea of it but I just cant explain it very well

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    $\begingroup$ You mean you can't find the formula $r_{\rm B} = GM/(v^2+c_s^2)$ or you are having a hard time interpreting it? $\endgroup$ Apr 23, 2020 at 19:41
  • $\begingroup$ @AtmosphericPrisonEscape probably "so far I have only rough idea of it but I just cant explain it very well" makes it pretty clear $\endgroup$
    – uhoh
    Apr 24, 2020 at 2:34
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    $\begingroup$ @uhoh As per usual, it would be better if you would not speak for other people, but let OP voice their opinion instead. $\endgroup$ Apr 24, 2020 at 8:51

1 Answer 1


From the mysterious site Vaporia, which is a fantastic index for astrophysics terms (and other things I'm seeing now):

The Bondi radius is analogous to the Hill radius, both giving an idea of how far from an object, a medium (gas, dust) is likely to be drawn in and accreted. The Bondi radius takes into account the (relative) speed of the object through the medium, and the medium's density and sound-speed. Accretion due to material falling within the Bondi radius is called Bondi accretion.

Try to picture a heavy object, perhaps a planet, travelling through a gaseous or dusty medium. Now, some of the gas is eventually going to be the victim of accretion to the planet. The planet is going to pull gas/dust from the medium and the Bondi radius tells you how far from the planet gas/dust is likely to be accreted to the planet.

Hopefully this is more clear!


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