The maximum mass of a neutron star is determined by a. electron degeneracy pressure b. neutron degeneracy pressure c. radiation pressure. d. none of the above

Neutron degeneracy pressure is a fundamental concept in astrophysics that explains why neutron stars can resist collapse under immense gravitational forces. When a massive star exhausts its nuclear fuel, its core can collapse under gravity, forming a neutron star.
Neutron stars are composed almost entirely of neutrons. These neutrons resist further compression due to the Pauli Exclusion Principle. This principle states that two fermions (like neutrons) cannot occupy the same quantum state simultaneously. As the core contracts, neutrons are packed closer together, increasing the pressure due to their degeneracy.
This degeneracy pressure works alongside nuclear forces between neutrons to balance the gravitational pull. It's this delicate balance that allows neutron stars to exist without collapsing into black holes. However, there is a limit to how massive a neutron star can be. Once the mass exceeds this limit (the Tolman–Oppenheimer–Volkoff limit), neutron degeneracy pressure can no longer hold up against gravity, leading to the formation of a black hole.

Understanding the structure of neutron stars helps us appreciate their complexity and unique properties. These stars, although only about 10-20 kilometers in diameter, have masses up to 2 times that of the Sun.
The outer crust of a neutron star is made up of heavy nuclei and a sea of electrons, forming a dense, solid layer. Beneath this crust lies the inner crust, where nuclei are packed closer together, and neutrons start to drip out, forming a neutron-rich 'soup'.
As we move inwards, we reach the outer core, composed largely of neutrons, with some protons and electrons. The particles here are in a superfluid state, meaning they move without friction. The inner core's exact composition is still a subject of research, but it's believed to contain exotic particles such as hyperons or deconfined quarks.
This layered structure is held together by gravitational attraction, with neutron degeneracy pressure playing a crucial role in stabilizing the star.

A supernova explosion is a potent and luminous event marking the end of a massive star's life cycle. When a star with a mass greater than eight times that of the Sun exhausts its nuclear fuel, it can no longer support its own weight.
The core collapses rapidly, leading to an incredible release of energy. This collapse triggers a shockwave that blows off the star's outer layers. The energy released in this explosion is in the form of light, heat, and neutrinos, making it one of the brightest events in the universe.
There are two main types of supernovae: Type I and Type II. Type I lacks hydrogen lines in their spectra, while Type II displays them, indicating different processes and progenitor stars.
The remnants of a supernova can form a neutron star if the core's mass is below the Tolman–Oppenheimer–Volkoff limit. If above, it can collapse further into a black hole. Supernovae play a vital role in enriching the interstellar medium with heavy elements, which are crucial for forming new stars and planets.