Question 1: A nebula is a cloud of gas and dust in space where stars are born. Describe the process by which a nebula evolves into a main sequence star.

Answer: A nebula contracts under gravity, increasing in temperature and pressure until nuclear fusion begins in the core, forming a main sequence star.

Question 1: Define a supernova and explain its role in the life cycle of massive stars.

Answer: A supernova is a powerful explosion that occurs at the end of a massive star's life, dispersing elements into space and often leaving behind a neutron star or black hole.

Question 2: Explain the difference between a neutron star and a black hole.

Answer: A neutron star is the dense remnant of a collapsed star composed mostly of neutrons, while a black hole is a region of space with gravity so strong that nothing can escape from it.

Question 1: Calculate the approximate lifespan of a star with a mass of 10 times that of the Sun, given that the Sun's lifespan is about 10 billion years. Use the proportional relationship: lifespan ∝ 1 / (mass)^2.

Answer: Lifespan ≈ 10 billion years / (10)^2 = 10 billion / 100 = 100 million years.

Question 2: A star has a radius of 7 × 10^8 meters and a mass of 2 × 10^30 kg. Calculate its average density in kg/m^3. Use the formula: Density = Mass / Volume, where Volume = (4/3)πr^3.

Answer: Volume = (4/3)π(7×10^8)^3 ≈ 1.436 × 10^27 m^3; Density = 2×10^30 kg / 1.436×10^27 m^3 ≈ 1.39×10^3 kg/m^3.

Question 1: Describe a theoretical experiment to investigate the effect of temperature on nuclear fusion in a star's core. Include variables and safety precautions.

Answer: Students could simulate fusion conditions using high-temperature plasma in a controlled laboratory setting, varying temperature to observe reaction rates. Variables include temperature (independent), reaction rate (dependent). Safety precautions involve high-temperature equipment, protective gear, and strict handling protocols for plasma.

Question 1: A star with a mass 20 times that of the Sun is observed to have a lifespan of approximately 10 million years. Explain how this observation supports the relationship between mass and lifespan.

Answer: The star's much shorter lifespan compared to the Sun supports the inverse square relation between mass and lifespan, indicating more massive stars burn their fuel faster.

Question 1: Explain the process by which a star becomes a black hole, including the necessary conditions and end stages. (6 marks)

Answer: A massive star exhausts its nuclear fuel, leading to core collapse under gravity. If the remaining core's mass exceeds the Tolman–Oppenheimer–Volkoff limit (~3 solar masses), it compresses into a black hole. The process involves supernova explosion and core collapse, resulting in a region of space with gravitational pull so strong that nothing can escape.

Question 1: Discuss how understanding the lifecycle of stars aids in the development of space exploration technology, such as spacecraft shielding or star mapping tools.

Answer: Knowledge of stellar evolution helps in predicting cosmic radiation levels and identifying stable star systems, improving spacecraft shielding design and navigation tools for missions.