Question 1: Define a nebula in the context of stellar evolution.

Answer: A nebula is a large cloud of gas and dust in space where new stars can form.

Question 2: Describe the main process that causes a star to evolve from a main sequence star into a supergiant.

Answer: As the star exhausts its hydrogen fuel in the core, nuclear fusion slows down, causing the core to contract and the outer layers to expand, forming a supergiant.

Question 3: Explain the difference between a neutron star and a black hole.

Answer: A neutron star is the remnants of a massive star after a supernova, composed mostly of neutrons; a black hole is a region of space with gravity so strong that not even light can escape, formed when a very massive star collapses beyond a neutron star stage.

Question 1: A star with a mass of 20 times that of the Sun undergoes a supernova. Calculate its approximate Schwarzschild radius. Use the formula R_s = 2GM / c^2, where G = 6.67×10^-11 Nm^2/kg^2, M is the mass, and c = 3×10^8 m/s.

Answer: R_s ≈ 59.2 km

Question 2: If a star's core contracts from a radius of 1 million km to a radius of 20 km during black hole formation, by what factor has the core contracted?

Answer: Factor of 50,000

Question 1: Design a theoretical experiment to simulate the process of a star's core collapsing into a black hole. Identify the main variables involved and discuss safety precautions for the experiment.

Answer: A simulation could involve high-energy particle collisions in a controlled environment (such as particle accelerators) to mimic core collapse dynamics. Variables include energy levels, particle types, and collision angles. Safety precautions must include shielding to protect against radiation, controlled access, and strict operational protocols.

Question 1: A star initially has a mass of 15 solar masses and ends its life as a neutron star. Describe the factors that determine whether it will become a neutron star or a black hole.

Answer: The key factor is the initial mass of the star. Stars with masses around 8-20 solar masses typically become neutron stars, while those exceeding about 20-25 solar masses may continue collapsing into black holes, depending on mass loss during evolution and core mass after supernova.

Question 1: Explain the main stages a star undergoes from forming in a nebula to potentially becoming a black hole. Include key processes and changes.

Answer: Stars form from nebulae through gravitational collapse, leading to nuclear fusion in the core. They spend most of their lives as main sequence stars, then expand into supergiants before ending their lives as supernovae. For very massive stars, the remnant core may collapse into a neutron star or black hole, depending on mass and other factors.

Question 2: What role does gravity play in the formation of black holes from massive stars?

Answer: Gravity causes the core of a massive star to collapse under its own weight once nuclear fusion stops, leading to the formation of a black hole when the core's gravity becomes so intense that not even light can escape.