In Newtonian physics, pressure is the force exerted per unit area and has the SI units Newtons per metre2 or Pascals (Pa).
In astronomy, pressure helps define the dimension of the stars. Gas and photon pressure try to make stars expand, whereas gravity tries to make them contract.
Stars on the main sequence are in a state of hydrostatic equilibrium, where the gravitational force and the gas pressure is in balance.
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