Astrophysics

• Spectral types range from O to M, with hotter stars having earlier letters (O-B) and cooler stars having later letters (A-M).
• Stars are classified based on their spectral type, which indicates their temperature and luminosity.
• The HR diagram can be used to determine whether a star will eventually become a red giant or white dwarf.
• Red giants have lower surface temperatures than main sequence stars but higher luminosities due to fusion occurring at the core rather than the surface.
• White dwarfs occur when all hydrogen has been fused into helium and there is no more fuel left for nuclear reactions.
• Supernovae occur when a massive star runs out of fuel and collapses under its own gravity.
• Black holes form when a massive star collapses under its own gravity.
• Black holes form when a massive star collapses under its own gravity during supernova explosions.
• Nebulae are clouds of gas and dust where new stars form through gravitational collapse.
• Neutron stars are incredibly dense objects with a mass greater than that of our sun packed into a sphere only about 10 km across.