GCSE Physics (AQA)

346 videos | 23 hours

Main Sequence Star

Please subscribe to watch this video.

This, and all other videos, are included in our premium subscriptions.

Premium accounts get access to all videos.

Space physics Solar system; stability of orbital motions; satellites

Main Sequence Star

2:59 Stars and the Solar System
Spec 4.8.1.1 4.8.1.2
Previous Stable Orbits Next The Doppler Effect
  • Main sequence stars are recently formed stars in the main stage of their lifetime.
  • Stars form when dust and gas in space are pulled together by gravity, leading to fusion of hydrogen atoms.
  • Fusion reactions distinguish main sequence stars from forming stars.
  • The sun is a main sequence star.
  • Main sequence stage lasts for millions of years until hydrogen in the core is depleted.
  • Fusion of hydrogen atoms results in helium atoms.
  • Once hydrogen is depleted, no more hydrogen fusion occurs in the core.
  • Lack of fusion causes the core to collapse due to gravity.
  • Normally, fusion provides outward pressure to oppose gravity, but without fusion, the core shrinks.
  • Core compression heats it up, allowing fusion of larger atoms.
  • Helium fusion depends on the star's size.
  • Increased pressure from fusion causes the star's outer shell to expand, become redder, and cool down.
  • Stronger fusion reaction results in stronger outward pressure, causing the star to expand and change color.
  • Although more heat is produced in the core, it is spread thinly, cooling the surface and reddening the color.
  • Detailed knowledge of these processes is not required at GCSE level.

Please subscribe to access these revision notes.

This, and all other video notes, are included in our premium subscriptions.

Premium accounts get access to all videos and revision notes.