Lesson 19

This lesson introduces stars as massive spheres of plasma powered by nuclear fusion. Use questioning, paired discussion, clear visual models and short sorting activities to help learners connect a star’s structure and energy production with its colour, surface temperature and spectral class. Emphasise the balance between inward gravity and outward pressure, address the common misconception that red stars are hotter than blue stars, and use the Sun as the main reference point for comparison. By the end of the lesson, learners should be able to describe how a stable star produces energy and explain how mass, temperature, colour and luminosity are related.