Astrophysics Fundamentals Flashcards
Grade 12 · Science · Flashcards
Essential terms for stars, galaxies, cosmology, and the physical laws of the universe.
Flashcards
- Luminosity
- The total energy output per unit time from a star, measured in watts or solar luminosities; distinct from apparent brightness.
- Apparent magnitude
- The brightness of a celestial object as seen from Earth; a logarithmic scale where lower values indicate brighter objects.
- Absolute magnitude
- The intrinsic brightness of a star as it would appear at a standard distance of 10 parsecs; a measure of true luminosity.
- Spectral class
- A classification of stars by surface temperature based on absorption spectra: O, B, A, F, G, K, M (hottest to coolest).
- Red giant
- A star in a late evolutionary stage that has exhausted core hydrogen; the outer layers expand and cool while the core contracts.
- Planetary nebula
- The glowing shell of gas expelled by a low-to-medium-mass star near the end of its life, leaving behind a white dwarf.
- Quasar
- An extremely luminous active galactic nucleus powered by matter accreting onto a supermassive black hole; visible across cosmic distances.
- Gravitational lensing
- The bending of light from a distant source by the gravity of a massive foreground object, predicted by general relativity.
- Dark energy
- A hypothetical form of energy (~68% of universe) driving the accelerating expansion of space, represented by the cosmological constant Λ.
- Nucleosynthesis
- The formation of atomic nuclei: Big Bang nucleosynthesis made H/He/Li; stellar nucleosynthesis forged heavier elements up to iron.
- Binary star system
- Two stars gravitationally bound to each other, orbiting a common center of mass; important for measuring stellar masses.
- Escape velocity
- The minimum speed required for an object to escape a gravitational field without further propulsion; depends on mass and radius of the body.
- Cosmic inflation
- A hypothetical period of exponential expansion of space in the first ~10⁻³² seconds after the Big Bang, explaining horizon and flatness problems.
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