Astrophysics is a core part of IB Physics. Revise the key concepts and common mistakes below, then lock them in with the free games.
Key concepts
Light-yearThe distance light travels in one year (~9.5×10¹⁵ m).
Orbital speedv = 2πr ÷ T for a body in a circular orbit.
Main sequence starA stable star fusing hydrogen to helium, gravity balanced by radiation pressure.
Red giant & white dwarfLate stages of a low-mass star's life.
SupernovaThe explosive death of a massive star, leaving a neutron star or black hole.
Red-shiftLight from distant galaxies stretched to longer wavelengths — the universe is expanding.
Common mistakes to avoid
Questions where students often pick the tempting wrong answer — make sure you know the right one:
What does red-shift of distant galaxies show?✗ The galaxies are red-hot. ✓ They are moving away — the universe is expanding.
What is a light-year?✗ A length of time. ✓ A distance — how far light travels in a year.
What happens to a star like the Sun at the end of its life?✗ It explodes as a supernova and forms a black hole. ✓ It becomes a red giant, then a white dwarf.
Practise Astrophysics — free games
Test yourself with these quick revision games for this topic:
See all 17 games in the Subjects Arcade →
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