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 P_{0}, the Bonnor–Ebert mass is given by


where G is the gravitational constant,

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

is the isothermal sound speed (\gamma = 1), and the dimensionless constant c_{BE} is given by

c_{BE} \simeq 1.18.

See also[edit]


  1. ^ Ebert, Rolf (1955). "Über die Verdichtung von H I-Gebieten". Zeitschrift für Astrophysik 37: 217. Bibcode:1955ZA.....37..217E. 
  2. ^ Bonnor, William Bowen (1956). "Boyle's Law and gravitational instability". Monthly Notices of the Royal Astronomical Society 116: 351. Bibcode:1956MNRAS.116..351B. 
  3. ^ Carroll, Bradley W.; Ostlie, Dale A. (2007). An Introduction to Modern Astrophysics. Addison-Wesley. pp. 413–414.