611 articles
Symplectic integrator
A symplectic integrator, also called a symplectic algorithm, is a numerical method for Hamiltonian systems whose steps preserve phase-space structure, making it standard for long-term planetary orbit integrations.
Synodic period
The synodic period is the time a solar system body takes to return to the same position relative to the Sun as seen from Earth, differing from the sidereal period.
Syzygy (astronomy)
Syzygy is an alignment of three or more celestial bodies in roughly a straight line, such as the Sun, Earth, and Moon at new or full moon.
Tachocline
The tachocline is a thin shear layer inside the Sun, about 0.7 solar radii from the center, where differential rotation transitions to uniform rotation in the interior.
Tagish Lake meteorite
The Tagish Lake meteorite is an ungrouped C2 carbonaceous chondrite that fell on January 18, 2000 over the Yukon and northern British Columbia, with fragments landing on frozen Tagish Lake.
Tai-pe Valles
Tai-pe Valles (Tai pe Valles) is a 400-km valley system on Venus at 11°N, 156.5°E, approved by the IAU in 1997 and named with the Chinese word for the planet Venus.
Taurids
The Taurids, also called the Taurid meteors, are an annual complex of meteor showers radiating from Taurus, tied to comet 2P/Encke and known for slow, bright fireballs.
Temporary satellite
A temporary satellite is a natural object, usually a small near-Earth asteroid, temporarily bound to a planet before escaping back into solar orbit, as with Earth's minimoons.
Terraforming of Venus
The terraforming of Venus is the hypothetical conversion of Venus's extreme carbon dioxide atmosphere to make its surface habitable, a problem studied since Carl Sagan's 1961 proposal.
Terrestrial planet
A terrestrial planet, also called a rocky or telluric planet, is a planet composed mainly of rock and iron with a solid or liquid surface, unlike the gas giants and ice giants.
Tethys (moon)
Tethys is a mid-sized icy moon of Saturn, its fifth largest satellite, discovered by Giovanni Cassini in 1684 and composed almost entirely of water ice.
Tetrad (eclipses)
A tetrad is a series of four consecutive total lunar eclipses, each about six months apart, whose frequency varies over centuries with Earth's orbital eccentricity.
Thalassa (moon)
Thalassa is a small inner moon of Neptune, discovered in August 1989 by Voyager 2. It orbits near the planet and shares an unusual orbital resonance with Naiad.
The Blue Marble
The Blue Marble is a 1972 photograph of the fully illuminated Earth taken by the Apollo 17 crew on the way to the Moon, showing Africa and Antarctica.
The Day the Earth Smiled
The Day the Earth Smiled was a July 19, 2013 event in which NASA's Cassini spacecraft photographed Saturn and Earth from within Saturn's shadow, after a public Wave at Saturn campaign.
The Last Days on Mars
The Last Days on Mars is a 2013 sci-fi horror film, Ruairí Robinson's feature debut, adapted from Sydney J. Bounds's short story "The Animators"; astronauts at Tantalus Base find bacterial life that turns the infected into zombies.
The Martian (Weir novel)
The Martian is a 2011 science fiction novel by Andy Weir, self-published online, in which astronaut Mark Watney survives alone on Mars through engineering and botany.
Themis family
Themis family: large, old outer main-belt asteroid family around (24) Themis, found by Hirayama in 1918; over 4,000 C/B-type members, 2.5 ± 1.0 Gyr old, water-ice rich, with main-belt comets and the young Beagle sub-family.
Themisto (moon)
Themisto, also designated Jupiter XVIII, is a small prograde irregular moon of Jupiter with a mean radius of about 4 kilometers, discovered in 1975, lost, and rediscovered in 2000.
Theobalda family
Theobalda family, asteroid family around (778) Theobalda in the outer main belt near 3.175 au; 128 members, 6.9 ± 2.3 Myr old, from a cratering impact on a ~78 km parent body; linked to main-belt comets P/2016 J1 and 427P.
Tidal acceleration
Tidal acceleration, also called tidal friction, is the transfer of angular momentum from Earth's rotation to the Moon's orbit, which makes the Moon recede about 3.8 cm per year.
Tidal bulge
A tidal bulge is an elongation of a body's oceans or solid interior toward and away from an attracting companion, caused by gravity's differing pull across the body.
Tidal circularization
Tidal circularization is the damping of orbital eccentricity in a binary system by tides raised on the bodies, causing the initially eccentric orbit to evolve toward a circular state.
Tidal disruption of binaries
Tidal disruption of binaries is the separation of a bound pair of small bodies passing close to a planet, which can split binaries or capture one member.
Tidal heating
Tidal heating is the generation of internal heat in a planet or moon by friction from repeated tidal flexing, powering Io's volcanism, Europa's subsurface ocean, and Enceladus's plumes.
Tidal locking
Tidal locking, also called synchronous rotation, is when a body's rotation matches its orbit so the same hemisphere always faces its companion, as the Moon does to Earth.
Tidal migration
Tidal migration is the gradual change in a body's orbit caused by tidal interactions, such as the Moon receding from Earth by 3.8 centimeters per year.
Tidal radius
The tidal radius is the distance from a star cluster or satellite galaxy at which a larger host's tidal force exceeds the body's own gravity, stripping material beyond it.
Tidal torque
Tidal torque is the torque exerted on a celestial body by a companion's gravity acting on its misaligned tidal bulge, governing tidal locking, orbital circularization, and despinning.
Timeline of discovery of Solar System planets and their moons
The timeline of discovery of Solar System planets and their moons, also called a timeline of discovery of moons, runs from naked-eye antiquity through telescopic, photographic, and spacecraft eras.