The Antikythera Mechanism A geared bronze astronomical calculator from ancient Greece, recovered from a shipwreck in 1901 — the most complex mechanical device to survive antiquity.
White Dwarfs The dense, cooling remnants of Sun-like stars supported by electron degeneracy pressure, with a maximum mass of about 1.4 solar masses.
Kepler's Laws of Planetary Motion The three empirical laws describing planetary orbits: ellipses, equal areas in equal times, and the relation between period and orbit size.
Black Holes Regions of spacetime where gravity is so strong that nothing, not even light, can escape from inside the event horizon.
Stellar Nucleosynthesis How stars build chemical elements from hydrogen through nuclear fusion, and how explosions and stellar winds spread them into space.