Table taenite TAI tail Tarantula Nebula T association Tau Ceti Taurids Taurus Taurus A Taurus-Littrow valley Tautenberg Taygeta TDB TDRSS TDT Teapot Tebbutt's Comet technetium star Teide Observatory tektite tele-compressor tele-extender telemetry telescope Telescope Telescopio Nazionale Galileo Telescopium Telesto telluric terminator terra terrestrial terrestrial dynamical time terrestrial planet tessera Tethys Thalassa Tharsis Ridge Thebe Themis Themis family Theophilus Theory of Relativity thermal radiation thermodynamic equilibrium third contact third quarter Thisbe tholus Thuban Thule tides time time zone Titan Titania Titius-Bode law TLP Tokyo Astronomical Observatory Tolles eyepiece topocentric coordinates Tornado Nebula Toro torus totality Toucan Toutatis Tracking and Data Relay Satellite System transient transient lunar phenomenon transit(1) transit(2) transit(3) transit circle transition probability transneptunian object Trapezium Triangle Triangulum Triangulum Australe Triangulum Galaxy Trifid Nebula trigonometric parallax triple-alpha process triplet triquetrum tri-Schiefspiegler Triton Trojan asteroids tropical month tropical year troposphere true anomaly Trumpler classification Tsiolkovskii Tsytovich-Razin effect T Tauri star T-type asteroid Tucana Tully-Fisher relation Tunguska event twenty-one-centimetre line twilight twinkling Twins two-colour diagram Tycho Tycho catalogue Tycho's Star Tyuratam