I' a tad stuck on there, could you help me?
Beginning of the solar system: Find out how a nebula can collapse under gravitational forces to create a protostar and accretion disc. Explain what happens to the conditions at the core of the protostar as it collapses further and at what point it becomes a star.
• Stable stars: What forces are at work in the sun at the present stage in its life cycle? How can it generate energy for billions of years yet remain in a stable state?
But did you bother to watch?