Can a White Dwarf Collapse into a Neutron Star Without a Supernova?

[PeterB]

Is it possible for white dwarf star in binary system where it is feeding off its partner star to collapse directly into a neutron star? Or is something inherent in the formation of neutron stars where they must be formed from supernova?

 

[phyzguy]

When a white dwarf accretes mass from a companion and exceeds the Chandrasekhar limit of about 1.4 solar masses, instead of collapsing to a neutron star, it explodes as a Type 1A supernova. The reason is that a white dwarf is formed of relatively light elements like carbon and oxygen, so there is still a lot of thermonuclear energy available from further fusion reactions. So when the star gets compressed further, these thermonuclear reactions ignite and the star explodes in a massive explosion. By contrast, when the core of a more massive star collapses to form a neutron star, the core is formed of heavier elements like iron. Since iron is at the peak of the nuclear binding energy curve, there is no more thermonuclear energy available from further fusion reactions.

 

[PeterB]

Thank you for you response, Would this mean that a neutron star which exceeds its Tolman-Oppenheimer-volkoff limit would always collapse to a black hole? Would fusion of Neutron star material (primarily neutrons) be possible?

 

[mathman]

Big neutron star collapse results in a black hole. The core of a neutron star can be thought of as the "fusion" of its neutrons. However there is no such thing as a fusion reaction in this case.

 

[phyzguy]

Thank you for you response, Would this mean that a neutron star which exceeds its Tolman-Oppenheimer-volkoff limit would always collapse to a black hole?

Yes, as far as we know this is the only outcome.