Bonnor-Ebert mass

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In astrophysics, the Bonnor-Ebert mass is the largest mass that an isothermal gas sphere embedded in a pressurized medium can have while still remaining in hydrostatic equilibrium. Clouds of gas with masses greater than the Bonnor-Ebert mass must inevitably undergo gravitational collapse to form much smaller and denser objects.[1] [2] As the gravitational collapse of an interstellar gas cloud is the first stage in the formation of a protostar, the Bonnor-Ebert mass is an important quantity in the study of star formation.[3]

For a gas cloud embedded in a medium with a gas pressure P0, the Bonnor-Ebert mass is given by

M_{BE}={c_{BE}v_{T}^4\over{P_{0}^{1\over{2}}G^{3\over{2}}}}

where G is the gravitational constant,

v_{T} \equiv \sqrt{kT\over{\mu m_{H}}}

is the isothermal sound speed (γ = 1), and the dimensionless constant cBE is given by

c_{BE} \simeq 1.18.

[edit] See also

[edit] References

  1. ^ Ebert, R. (1955). "Über die Verdichtung von H I-Gebieten". Zeitschrift für Astrophysik 37: 217. 
  2. ^ Bonnor, W. B. (1956). "Boyle's Law and gravitational instability". MNRAS 116: 351. 
  3. ^ Carroll, Bradley W. & Ostlie, Dale A. (2007). An Introduction to Modern Astrophysics. Addison-Wesley, 413-414. 
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