Question 1: Define the Main Sequence in the context of stellar evolution.

Answer: The Main Sequence is the continuous and distinctive band of stars on the Hertzsprung-Russell diagram where stars fuse hydrogen into helium in their cores, representing a stable period in a star's lifecycle.

Question 2: Explain the primary nuclear process occurring in stars during the Main Sequence phase.

Answer: Stars in the Main Sequence primarily fuse hydrogen nuclei into helium through nuclear fusion in their cores, releasing energy that balances gravitational collapse.

Question 1: Calculate the luminosity (L) of a star with a radius of 1.5 times the Sun's radius (R☉ = 6.96 x 10^8 m) and an effective temperature of 6000 K. Use the Stefan-Boltzmann Law: L = 4πR^2σT^4, where σ = 5.67 x 10^-8 W/m^2K^4.

Answer: L ≈ 3.78 x 10^26 Watts

Question 2: A star has an effective temperature of 5500 K and a radius equal to twice that of the Sun. Calculate its approximate surface area and comment on its relative brightness compared to the Sun.

Answer: Surface area ≈ 1.76 x 10^19 m^2; it has a larger surface area and higher luminosity, so it is brighter than the Sun.

Question 1: Describe a basic experimental setup to demonstrate the thermal radiation emitted by hot objects, analogous to stellar radiation. Include key variables to control and measure.

Answer: Set up a blackbody emitter or a heated metal object in a dark room. Control variables include temperature (by adjusting heat source), distance from the detector, and material. Measure the emitted radiation using a spectrometer or infrared sensor to observe the relationship between temperature and emitted radiation spectrum.

Question 2: Identify three safety precautions necessary when conducting experiments involving high temperatures or radiation sources.

Answer: Use heat-resistant gloves and safety goggles, ensure proper ventilation, and keep a safe distance from hot objects or radiation sources.

Question 1: A star has a surface temperature of 5800 K and a radius 1.2 times that of the Sun. Using the Stefan-Boltzmann Law, estimate its luminosity relative to the Sun's luminosity. Assume the Sun's luminosity as 3.83 x 10^26 W.

Answer: Luminosity ≈ 1.44 times that of the Sun

Question 1: Explain how the process of nuclear fusion in the core of a Main Sequence star maintains its stability over millions of years. Include the balance between gravitational force and radiation pressure in your answer.

Answer: Nuclear fusion in the core converts hydrogen into helium, releasing energy that produces radiation pressure outward. This pressure balances the inward pull of gravity, maintaining the star's stability. The process is self-regulating: if the core cools, fusion slows, causing contraction and heating, which increases fusion again, restoring equilibrium.

Question 1: Describe how knowledge of stellar radiation and nuclear fusion contributes to advancements in nuclear energy technology on Earth.

Answer: Understanding stellar nuclear fusion helps scientists develop controlled fusion reactors, which aim to produce clean, abundant energy by replicating the fusion processes occurring in stars.