Bonnor-Ebert mass
Encyclopedia
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.
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
.
For a gas cloud embedded in a medium with a gas pressure
, the Bonnor–Ebert mass is given by
where G is the gravitational constant
,
is the isothermal sound speed (
), and the dimensionless constant
is given by
Astrophysics
Astrophysics is the branch of astronomy that deals with the physics of the universe, including the physical properties of celestial objects, as well as their interactions and behavior...
, 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
Hydrostatic equilibrium
Hydrostatic equilibrium or hydrostatic balance is the condition in fluid mechanics where a volume of a fluid is at rest or at constant velocity. This occurs when compression due to gravity is balanced by a pressure gradient force...
.
Clouds of gas with masses greater than the Bonnor–Ebert mass must inevitably undergo gravitational collapse
Gravitational collapse
Gravitational collapse is the inward fall of a body due to the influence of its own gravity. In any stable body, this gravitational force is counterbalanced by the internal pressure of the body, in the opposite direction to the force of gravity...
to form much smaller and denser objects.
As the gravitational collapse of an interstellar gas cloud is the first stage in the formation of a protostar
Protostar
A protostar is a large mass that forms by contraction out of the gas of a giant molecular cloud in the interstellar medium. The protostellar phase is an early stage in the process of star formation. For a one solar-mass star it lasts about 100,000 years...
, the Bonnor–Ebert mass is an important quantity in the study of star formation
Star formation
Star formation is the process by which dense parts of molecular clouds collapse into a ball of plasma to form a star. As a branch of astronomy star formation includes the study of the interstellar medium and giant molecular clouds as precursors to the star formation process and the study of young...
.
For a gas cloud embedded in a medium with a gas pressure
, the Bonnor–Ebert mass is given bywhere G is the gravitational constant
Gravitational constant
The gravitational constant, denoted G, is an empirical physical constant involved in the calculation of the gravitational attraction between objects with mass. It appears in Newton's law of universal gravitation and in Einstein's theory of general relativity. It is also known as the universal...
,
is the isothermal sound speed (
), and the dimensionless constantDimensionless quantity
In dimensional analysis, a dimensionless quantity or quantity of dimension one is a quantity without an associated physical dimension. It is thus a "pure" number, and as such always has a dimension of 1. Dimensionless quantities are widely used in mathematics, physics, engineering, economics, and...
is given by