[{"n": "Cosmic inflation", "u": "/e/astronomy/cosmic-inflation/", "s": "A theory of exponential expansion of space in the very early universe, explaining the large-scale structure an"}, {"n": "Cosmic ray", "u": "/e/astronomy/cosmic-ray/", "s": "High-energy particles from space, discovered via balloon flights in 1912."}, {"n": "Cosmological constant", "u": "/e/astronomy/cosmological-constant/", "s": "A coefficient in Einstein's equations explaining cosmic acceleration."}, {"n": "Crab Nebula", "u": "/e/astronomy/crab-nebula/", "s": "A supernova remnant and pulsar wind nebula in Taurus, linked to a supernova observed in AD 1054."}, {"n": "Dark nebula", "u": "/e/astronomy/dark-nebula/", "s": "Dark patches in the Milky Way that block visible light"}, {"n": "Dwarf galaxy", "u": "/e/astronomy/dwarf-galaxy/", "s": "Small galaxies shaped by larger neighbors and dark matter."}, {"n": "Eris (dwarf planet)", "u": "/e/astronomy/eris-dwarf-planet/", "s": "Dwarf planet whose discovery redefined the Solar System's planetary lineup."}, {"n": "Event horizon", "u": "/e/astronomy/event-horizon/", "s": "A spacetime boundary beyond which no signal can reach an observer."}, {"n": "Exoplanet", "u": "/e/astronomy/exoplanet/", "s": "An exoplanet, also called an extrasolar planet, is any planet that exists beyond our Solar System."}, {"n": "Extinction (astronomy)", "u": "/e/astronomy/extinction-astronomy/", "s": "Extinction dims and reddens starlight via interstellar dust and gas."}, {"n": "Extraterrestrial life", "u": "/e/astronomy/extraterrestrial-life/", "s": "Hypothetical life originating from worlds beyond Earth."}, {"n": "Galaxy formation and evolution", "u": "/e/astronomy/galaxy-formation-and-evolution/", "s": "Study of galaxy origins, structure, and change over cosmic time."}, {"n": "Galaxy groups and clusters", "u": "/e/astronomy/galaxy-groups-and-clusters/", "s": "Largest gravitationally bound objects in cosmic structure formation."}, {"n": "Galaxy morphological classification", "u": "/e/astronomy/galaxy-morphological-classification/", "s": "A system for classifying galaxies by visual appearance and structure."}, {"n": "Giant planet", "u": "/e/astronomy/giant-planet/", "s": "A massive planet composed mainly of volatiles, not solid matter."}, {"n": "Giant star", "u": "/e/astronomy/giant-star/", "s": "Giant stars are luminous, expanded post-main-sequence stars."}, {"n": "H II region", "u": "/e/astronomy/h-ii-region/", "s": "Ionized hydrogen regions where new stars are born."}, {"n": "Halley's Comet", "u": "/e/astronomy/halley-s-comet/", "s": "First comet recognized as periodic, observed for over two millennia."}, {"n": "Hertzsprung–Russell diagram", "u": "/e/astronomy/hertzsprung-russell-diagram/", "s": "Scatter plot linking stellar luminosity and temperature."}, {"n": "Hubble's law", "u": "/e/astronomy/hubble-s-law/", "s": "Galaxies recede faster the farther they are from Earth."}, {"n": "Hyades (star cluster)", "u": "/e/astronomy/hyades-star-cluster/", "s": "Nearest open cluster, key rung on the cosmic distance ladder."}, {"n": "Elliptical galaxy", "u": "/e/astronomy/elliptical-galaxy/", "s": "Elliptical galaxies are smooth, ellipsoidal galaxies with old stars."}]