What is the maximum mass of a star? What kind of pressure limits how massive a star can be?

What is the maximum mass of a star? What kind of pressure limits how massive a star can be?What is the maximum mass of a star? What kind of pressure limits how massive a star can be?Since the more mass a star has, the more energy it will produce, there is a balance of pressures. The upper limit seems to be around 150 solar masses, but its not due to gravitational collapse. Actually, it is the energy output that gets too intense for the star's gravitational pull to maintain cohesion. At this point, the star's radiance expels the star's outer layers, therefore reducing its mass.



For a white dwarf, what balances the inward gravitational pull is the electron degeneracy pressure. The atoms in the star get so densely packed that the only thing that keeps further collapse is it's atom's electrons impossibility of occupying the same quantum state, by the Pauli exclusion principle. In other words, quantum effects that stops electrons from getting closer balances the star's gravity. This effect holds up to 1.4 solar masses, the Chandrasekhar limit. Past that, the white dwarf will collapse further to become a neutron star or a black hole.



In a neutron star, the gravitational pressure forced the star past the electron degeneracy level. The electrons fuse with protons becoming neutrons and emitting a neutrino (electron capture). The star now is mainly composed of neutrons. The next thing that can stop full collapse is again the exclusion principle, this time for the neutrons. Strong force also has a role in repelling neutrons. If the star's mass is greater than 1.5 to 3 solar masses (the Tolman鈥揙ppenheimer鈥揤olkoff limit), the neutrons too won't hold.



Only theoretically, the collapse may be again stopped when the neutrons break down to quarks. It is now sustained by the Strong nuclear force. This would be called a quark star, but remains only theoretical. The upper mass limmit is not yet defined.



After this step, if the mass is too great (or if you skip this step, as it hasn't been observed), no force can counter balance the star's gravity and it collapses infinitely to a point known as a singularity. It is surrounded by an event horizon and the ex-star is now a black hole.