Today, while discussing the life cycle of stars, one of my students asked what factor determines whether a massive star becomes a neutron star or a black hole after its explosion. I knew that it depended on the mass of the star but nothing else beyond that, so I asked ChatGPT. Should I consider it as a credible source? The answer is posted below. Bryan Dibble Curtis Greeley
Whether a massive star becomes a neutron star or a black hole depends primarily on the star's mass after it undergoes a supernova explosion, which is part of the star's final stages of evolution.
Here’s a breakdown:
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Neutron Star Formation:
- When a massive star (between about 8 to 20–25 times the mass of the Sun) exhausts its nuclear fuel, it can no longer support itself against gravity, and its core collapses.
- The outer layers are ejected in a supernova explosion, and the core is compressed into a very dense object made mostly of neutrons.
- If the remaining core’s mass (after the explosion) is below a certain limit (about 1.4 to 3 solar masses, called the Tolman-Oppenheimer-Volkoff limit), the pressure from neutrons is enough to halt further collapse, leading to the formation of a neutron star.
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Black Hole Formation:
- If the core's remaining mass exceeds about 3 solar masses, even neutron degeneracy pressure (the force preventing further collapse in a neutron star) cannot stop the gravitational collapse.
- The core continues to collapse under its own gravity until it forms a black hole, where the escape velocity exceeds the speed of light, and not even light can escape.
Summary:
- Neutron star: Forms when the core remnant mass is below the upper limit (~3 solar masses).
- Black hole: Forms when the core remnant mass exceeds this limit.
The exact boundary between forming a neutron star and a black hole depends on several factors, including the initial mass of the star and the details of the supernova explosion.
