Solar System bodies

Saturn's hexagon

Saturn's hexagon is a persistent six-sided pattern in an eastward jet stream around Saturn's north pole, discovered in Voyager images from 1980 and 1981 and visible ever since.

Saykal Fossae

Saykal Fossae is a 300-km-long, narrow tectonic depression (fossa) on Venus at 73N, 139E, named by the IAU in 1997 for a Kyrgyz warrior maiden, one of 32 named Venusian fossae.

Setebos (moon)

Setebos is a small, dark irregular moon of Uranus, discovered in 1999, orbiting retrograde more than 11 million miles away and about 30 miles in diameter.

Sholpan Vallis

Sholpan Vallis, a 590 km valley on Venus at 63.9S 150E, named for the Kazakh and Karakalpak word for Venus, IAU-approved in 2003, one of 72 Venusian valles.

Sinann Vallis is a 425-km-wide channel system (vallis) on Venus at 49S, 270E, approved by the IAU in 1994 and named for an Irish river goddess; it consists of disconnected lava-channel traces over 1,000 km long.

Sinope (moon)

Sinope is a small retrograde irregular moon of Jupiter, about 19 km in radius, discovered by Seth Barnes Nicholson at Lick Observatory in 1914 and named for a nymph who outwitted Zeus.

Skathi (moon)

Skathi (Saturn XXVII, formerly spelled Skadi) is a small irregular moon of Saturn about 8 kilometers across, discovered on September 23, 2000, and named for the Norse giantess Skadi.

SMASS classification

The SMASS classification, also called the Bus or Bus–Binzel taxonomy, classifies asteroids by visible-wavelength reflectance spectra, defining 26 classes grouped into S, C, and X complexes.

Solar Activity

Solar activity: magnetic phenomena on the Sun, including sunspots, solar flares, coronal mass ejections, solar wind, and solar energetic particles, varying over an 11-year solar cycle and driving space weather that affects satellites, GPS, radio, and power grids on Earth.

Solar campfires

Solar campfires are small, transient extreme-ultraviolet brightenings in the quiet solar corona, first seen in 2020 by Solar Orbiter and studied as possible contributors to heating the Sun's million-degree corona.

Solar composition

Solar composition is the measured abundance of chemical elements in the Sun, determined from photospheric spectroscopy, CI chondrite meteorites, and Genesis solar wind samples; it serves as the reference for stellar chemistry.

Solar core

The solar core is the Sun's central region, where nuclear fusion of hydrogen into helium produces about 98% of the Sun's energy at roughly 15,000,000 °C.

Solar corona

The solar corona, also called the Sun's corona, is the outermost layer of the Sun's atmosphere, hotter than the surface below it at over 1 million degrees Celsius.

Solar cycle

The solar cycle, also known as the Schwabe or sunspot cycle, is the roughly 11-year rise and fall of the Sun's magnetic activity, tracked by sunspot numbers.

Solar cycle prediction

Solar cycle prediction is the forecasting of the amplitude and timing of an upcoming or ongoing solar cycle, the Sun's roughly 11-year oscillation in magnetic activity.

Solar dynamo

The solar dynamo is the hydromagnetic process inside the Sun that generates its large-scale magnetic field, driving the 11-year sunspot cycle and the 22-year polarity reversal cycle.

Solar flare

A solar flare, also called a Sun flare, is an intense burst of radiation from magnetic energy at sunspots, the solar system's most powerful explosion.

Solar granulation

Solar granulation is the mottled pattern of bright convection cells on the Sun's surface, where granules 700 to 1000 km wide live 5 to 10 minutes.

Solar irradiance variability

Solar irradiance variability is the variation over time of the Sun's radiant power at Earth, averaging about 1361 W/m² and fluctuating roughly 0.1% over the 11-year solar cycle.

Solar luminosity

Solar luminosity is the total rate at which the Sun emits energy, about 3.828×10²⁶ watts; astronomers use it as a standard unit for expressing other stars' power output.

Solar magnetic field

The solar magnetic field is the magnetic field generated inside the Sun by a dynamo, producing sunspots and flares, with polarity reversing roughly every 11 years.

Solar prominence

A solar prominence is a large, bright structure of cool, dense plasma extending from the Sun's surface into the hot corona, held by magnetic fields; many erupt, driving space weather.

Solar System

The Solar System, also called our solar system, is the Sun and everything orbiting it: eight planets, hundreds of moons, and billions of smaller bodies.

Sponde

Sponde (Jupiter XXXVI) is a small retrograde irregular moon of Jupiter in the Pasiphae group, discovered in 2001 at Mauna Kea and named for one of the Horae.

Stephano (moon)

Stephano (Uranus XX, provisional designation S/1999 U2) is a small, dark retrograde irregular moon of Uranus about 32 kilometers wide, discovered in 1999 and named after a butler in Shakespeare's The Tempest.

Subglacial lake on Mars

The subglacial lake on Mars is a putative body of liquid water proposed in 2018 beneath the south polar ice cap, based on radar reflections that remain contested.

Subglacial water on Mars

Subglacial water on Mars is hypothesized liquid water beneath the planet's ice, notably a putative lake 1.5 km below the south polar cap reported in 2018.

Subsurface ocean of Enceladus

The subsurface ocean of Enceladus is a global body of liquid saltwater between the icy shell and rocky core of Enceladus, a moon of Saturn, confirmed by Cassini in stages from 2014 to 2017.

Sun

The Sun, also known as Star Sol, is the G2 yellow dwarf star at the center of the Solar System, about 4.57 billion years old.