aberration accretion disc AGN Alpha Centauri angular diameter distance apoapsis asteroid asteroid belt astronomy binary star black hole brown dwarf Callisto celestial latitude celestial longitude cluster coma comet conjunction cosmic dust cosmological constant Crab Nebula dark matter declination double star Earth eclipse emission line epoch equinox Europa galactic plane galaxy gamma ray burst Ganymede Halley's comet heliosphere hour angle Hubble's constant Hubble's Law inclination inferior conjunction interstellar medium Io Jupiter Kepler's law Kepler's law of planetary motion luminosity Magellanic Cloud Mars mean solar time mean time Mercury meteorite meteoroid Milky Way moon nebula nebular nebulus Neptune neutron star Oort cloud orbit orbital plane Orion periapsis phase planet Pleiades Pluto point of apoapsis point of periapsis precession protostar quasar radio astronomy radio telescope red dwarf red giant Red Planet red shift retrograde right ascension rotation curve satellite Saturn SETI spiral galaxy star star formation sub-millimetre sun supercluster supergiant superior superior conjunction supernova telescope terrestrial time universe Uranus variable star Venus vernal equinox white dwarf