300 articles
Supergranulation
Supergranulation is a cellular pattern of mostly horizontal flows on the Sun's surface, with cells about 30,000 km across that last one to two days.
Sycorax (moon)
Sycorax is the largest known irregular moon of Uranus, about 150 km across, discovered on 6 September 1997 at Palomar Observatory and named for Caliban's mother in Shakespeare's The Tempest.
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.
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.
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.
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.
Titan (moon)
Titan is Saturn's largest moon and the second largest in the solar system, the only moon with a dense atmosphere, with liquid methane and ethane seas on its surface.
Toharu (crater on Ceres)
Toharu is an 86-km-diameter impact crater on the dwarf planet Ceres at 48.32°S, 155.95°E, named for a Pawnee god, with a central peak cut by a pit indicating subsurface ice.
TOI-1338 b
TOI-1338 b, also known as BEBOP-1b, is a circumbinary planet orbiting two stars in the constellation Pictor about 1,300 light-years away, the first discovered by NASA's TESS in 2020.
Transition region (Sun)
The transition region is a thin layer of the Sun's atmosphere separating the hot corona from the cooler chromosphere, where the temperature drops from about 1,000,000°C to 20,000°C.
Transition Region and Coronal Explorer
The Transition Region and Coronal Explorer (TRACE) was a NASA Small Explorer satellite that imaged the Sun's transition region and corona in ultraviolet light from 1998 to 2010.
Trinculo (moon)
Trinculo, formally Uranus XXI, is a small, dark irregular moon of Uranus in a retrograde orbit, about 11 miles (18 km) wide, discovered in 2001.
Triton (moon)
Triton, designated Neptune I, is the largest moon of Neptune, discovered by William Lassell in 1846. It orbits retrograde and is a candidate ocean world.
Uhola Catenae
Uhola Catenae: chains of troughs and elongated pits on dwarf planet Ceres, north of the Yalode basin; IAU-named 2016 after a Nigerian harvest festival; 400 km across, partly radial to Yalode.
Umbriel
Umbriel (Uranus II) is the third largest and darkest of Uranus's five classical moons, a heavily cratered icy body about 1,200 km wide, discovered by William Lassell in 1851.
Uottakh-sulus Valles
Uottakh-sulus Valles, a 1,100-km lava channel system (valles) on Venus at 12.5N, 239.0E, IAU-approved 1997; named with the Yakutian/Saha word for the planet Venus.
Uranus
Uranus is the seventh planet from the Sun, an ice giant tipped on its side, discovered by William Herschel in 1781 and visited once by Voyager 2 in 1986.
Venus
Venus, also called Sol II, is the second planet from the Sun, an Earth-sized world heated to 464 °C by a carbon-dioxide atmosphere 92 times heavier than Earth's.
Volcanism on Io
Volcanism on Io is the volcanic activity of Jupiter's moon Io, the most volcanically active body in the solar system, powered by tidal heating with about 400 volcanoes.
Vulcan (hypothetical planet)
Vulcan, also called Planet Vulcan, was a hypothetical planet proposed by Le Verrier in the 19th century to explain Mercury's orbit, never found; Einstein explained the anomaly in 1915.
WASP-12b
WASP-12b is a hot Jupiter exoplanet discovered in 2008 by SuperWASP, orbiting its late-F star every 1.09 days at 0.0234 AU. It is inflated, tidally stripped, carbon-debate famous, and the only hot Jupiter with a confirmed decaying orbit.
Water on Mars
Water on Mars refers to water now on Mars, mostly ice, hydrated minerals, and vapor, plus strong evidence that rivers and lakes existed over 3 billion years ago.
Water vapor plumes on Europa
Water vapor plumes on Europa are putative eruptions of water vapor from Jupiter's moon Europa, first reported in 2012, whose existence a 2026 reanalysis called into question.
Wide-field Infrared Survey Explorer
The Wide-field Infrared Survey Explorer (WISE) was a NASA infrared space telescope launched in 2009 that mapped the entire sky, then hunted asteroids as NEOWISE until 2024.
Wolf number
The Wolf number, also called the relative sunspot number, is a daily index of solar activity computed from sunspot counts, devised by Rudolf Wolf in 1848.