Astrophysics and the Universe Flashcards

Grade 12 · Science · Flashcards

Key astrophysics vocabulary for Grade 12 Science.

Flashcards

Nebula: A cloud of gas and dust in space; the birthplace of stars; also the remnant of a dead star (planetary nebula).
Main sequence: Stable phase of stellar life; core hydrogen fusion balances gravity; Sun has ~5 billion years left.
Red giant: Expanded, cooler stage when a medium-mass star exhausts core hydrogen; Sun will become one in ~5 billion years.
White dwarf: Dense, Earth-sized remnant of a low-to-medium mass star after shedding outer layers; no longer fuses fuel.
Supernova: Catastrophic explosion of a massive star; briefly outshines the galaxy; disperses elements into space.
Neutron star: Ultra-dense stellar remnant after supernova; composed almost entirely of neutrons; ~20 km diameter.
Black hole: Region where gravity is so extreme that escape velocity > c; formed from very massive stellar remnants.
Hertzsprung-Russell diagram: Star classification chart plotting luminosity vs. surface temperature; main sequence diagonal from top-left to bottom-right.
Big Bang theory: Universe began ~13.8 billion years ago from a hot, dense singularity; supported by CMB and redshift evidence.
Hubble's Law: v = H₀d; galaxy recession velocity proportional to distance; H₀ ≈ 70 km/s/Mpc.
Dark matter: Non-luminous matter (~27% of universe mass-energy); detected only via gravitational lensing and galaxy rotation curves.
Cosmic microwave background: Thermal radiation afterglow of Big Bang (~2.7 K today); fills universe uniformly; detected in 1965.