When a red giant star collapses due to gravitational collapse, it undergoes a dramatic transformation known as a supernova. A supernova is a powerful explosion that releases an immense amount of energy, making it one of the most energetic events in the universe.
The collapse of the red giant's core occurs when the nuclear fusion reactions that sustain the star's structure can no longer counterbalance the inward pull of gravity. This collapse happens rapidly, and the core becomes incredibly dense. The collapse halts when the core reaches a critical density, and then a rebound occurs due to the strong nuclear forces between particles. This rebound generates a shockwave that propagates outward, causing the outer layers of the star to be violently expelled into space.
The explosion of a supernova releases an enormous amount of energy in the form of intense radiation and the ejection of stellar material. During the explosion, the star becomes incredibly bright and can briefly outshine an entire galaxy. Supernovae play a crucial role in dispersing heavy elements synthesized in the star's core, which then enriches the surrounding interstellar medium, contributing to the formation of new stars and planetary systems.
Depending on the initial mass of the red giant star, the collapse and subsequent supernova can lead to different outcomes. For stars with masses up to about eight times that of the Sun, the core collapse results in a dense remnant known as a neutron star. Neutron stars are incredibly compact and contain a high concentration of neutrons.
For more massive stars, typically those with masses above eight times that of the Sun, the core collapse can lead to the formation of a black hole. A black hole is an object with such intense gravitational pull that nothing, not even light, can escape from it.
In summary, when the orbit of a red giant collapses due to gravitational collapse, it undergoes a supernova explosion. The specific outcome depends on the initial mass of the star, with lower mass stars resulting in neutron stars and more massive stars potentially leading to the formation of black holes.