List of exceptional asteroids

second-largestList of notable asteroidsfourth-largest asteroid
List of minor planet moons. List of Venus-crossing minor planets. List of Earth-crossing minor planets. List of Jupiter-crossing minor planets. List of Mars-crossing minor planets. List of Mercury-crossing minor planets. List of Neptune-crossing minor planets. List of Saturn-crossing minor planets. List of Solar System objects by size. List of Uranus-crossing minor planets. Lists of astronomical objects. Scattered disc object. Small Solar System body. ʻOumuamua. Lists and plots: Minor Planets. PDS Asteroid Data Archive. SBN Small Bodies Data Archive. NASA Near Earth Object Program. Major News About Minor Objects.

International Astronomical Union

IAUWorking Group for Planetary System NomenclatureInternational Astronomical Union (IAU)
The Minor Planet Center also operates under the IAU, and is a "clearinghouse" for all non-planetary or non-moon bodies in the Solar System. The Working Group for Meteor Shower Nomenclature and the Meteor Data Center coordinate the nomenclature of meteor showers. The IAU was founded on 28 July 1919, at the Constitutive Assembly of the International Research Council (now the International Science Council) held in Brussels, Belgium. Two subsidiaries of the IAU were also created at this assembly: the International Time Commission seated at the International Time Bureau in Paris, France, and the International Central Bureau of Astronomical Telegrams initially seated in Copenhagen, Denmark.


starsstellarmassive star
Other than the Sun, the star with the largest apparent size is R Doradus, with an angular diameter of only 0.057 arcseconds. The disks of most stars are much too small in angular size to be observed with current ground-based optical telescopes, and so interferometer telescopes are required to produce images of these objects. Another technique for measuring the angular size of stars is through occultation. By precisely measuring the drop in brightness of a star as it is occulted by the Moon (or the rise in brightness when it reappears), the star's angular diameter can be computed.

Tethys (moon)

Tethysquadrangle of the moon Tethysthird moon
This can partially explain why Saturnian moons including Tethys contain more water ice than outer Solar System bodies like Pluto or Triton as the oxygen freed from carbon monoxide would react with the hydrogen forming water. One of the most interesting explanations proposed is that the rings and inner moons accreted from the tidally stripped ice-rich crust of a Titan-like moon before it was swallowed by Saturn. The accretion process probably lasted for several thousand years before the moon was fully formed. Models suggest that impacts accompanying accretion caused heating of Tethys's outer layer, reaching a maximum temperature of around 155 K at a depth of about 29 km.

Dysnomia (moon)

DysnomiaEris I Dysnomia(136199) Eris I Dysnomia
Impacts between bodies of the order of 1000 km across would throw off large amounts of material that would coalesce into a moon. A similar mechanism is thought to have led to the formation of the Moon when Earth was struck by a giant impactor early in the history of the Solar System. Mike Brown, the moon's discoverer, chose the name Dysnomia due to a number of associations it had for him. Dysnomia, the daughter of Eris, fits the general historically established pattern of naming moons after lesser gods associated with the primary god (hence, Jupiter's largest moons are named after lovers of Jupiter, both male and female, while Saturn's are named after his fellow Titans).

Miranda (moon)

Miranda MirandaMiranda, Uranus
. * List of geological features on Miranda Miranda Profile at NASA's Solar System Exploration site. Miranda page at The Nine Planets. Miranda, a Moon of Uranus at Views of the Solar System. Paul Schenk's 3D images and flyover videos of Miranda and other outer solar system satellites. Miranda Nomenclature from the USGS Planetary Nomenclature web site.

Invariable plane

common orbital alignmentinvariable plane of the Solar System“invariable” axis
That of Jupiter contributes the bulk of the Solar System's angular momentum, 60.3%. Then comes Saturn at 24.5%, Neptune at 7.9%, and Uranus at 5.3%. The Sun forms a counterbalance to all of the planets, so it is near the barycenter when Jupiter is on one side and the other three jovian planets are diametrically opposite on the other side, but the Sun moves to 2.17 solar radii away from the barycenter when all jovian planets are in line on the other side. The orbital angular momenta of the Sun and all non-jovian planets, moons, and small Solar System bodies, as well as the axial rotation momenta of all bodies, including the Sun, total only about 2%.

Scott S. Sheppard

S. S. SheppardScott SheppardSheppard
., being only the third known after 2012 VP113 and Sedna, further demonstrated that a super-Earth planet in the distant solar system likely exists as 2015 TG387 has many orbital similarities as the two other known inner Oort cloud objects. Sheppard has been involved in the discovery of many small Solar System bodies such as trans-Neptunian objects, centaurs, comets and near-Earth objects.

Radioactive decay

radioactiveradioactivitydecay mode
There are 28 naturally occurring chemical elements on Earth that are radioactive, consisting of 34 radionuclides (6 elements have 2 different radionuclides) that date before the time of formation of the Solar System. These 34 are known as primordial nuclides. Well-known examples are uranium and thorium, but also included are naturally occurring long-lived radioisotopes, such as potassium-40.

Deimos (moon)

DeimosDeimos moonMars II
List of missions to the moons of Mars. List of natural satellites. Moons of Mars. Phobos and Deimos in fiction. Transit of Deimos from Mars. Deimos Profile by NASA's Solar System Exploration. Deimos rotation movie. Animation of Deimos. 3D model of Deimos. USGS Deimos nomenclature.

Uncrewed spacecraft

Unmannedunmanned spacecraftuncrewed
For a more detailed list, see List of Solar System probes. Luna program — USSR Lunar exploration (1959–1976). Ranger program — US Lunar hard-landing probes (1961–1965). Zond program — USSR Lunar exploration (1964–1970). Surveyor program — US Lunar soft-landing probe (1966–1968). Lunar Orbiter program — US Lunar orbital (1966–1967). Lunokhod program — USSR Lunar Rover probes (1970–1973). MUSES-A (Hiten and Hagoromo) — Japanese Lunar orbital and hard-landing probes (1990–1993). Clementine — US Lunar orbital (1998). Lunar Prospector — US Lunar orbital (1998–1999). Smart 1 — European Lunar orbital (2003). SELENE — Japanese lunar orbiter (2007). Chang'e 1 — Chinese lunar orbiter (2007).

Extraterrestrial liquid water

liquid waterExtraterrestrial waterinternal aquatic ocean
For the Jovian moons Ganymede and Europa, the existence of a sub-ice ocean is inferred from the measurements of the magnetic field of Jupiter. Since conductors moving through a magnetic field produce a counter-electromotive field, the presence of the water below the surface was deduced from the change in magnetic field as the moon passed from the northern to southern magnetic hemisphere of Jupiter. Thomas Gold has posited that many Solar System bodies could potentially hold groundwater below the surface. It is thought that liquid water may exist in the Martian subsurface.


Orbit of the Moon. Stability of the Solar System. Tellurion. Torquetum. JPL Solar System Simulator. Long Now Foundation Orrery. University of Pennsylvania Orrery.

Opposition (astronomy)

oppositionoppositionsOpposition (planets)
Because most orbits in the Solar System are nearly coplanar to the ecliptic, this occurs when the Sun, Earth, and the body are configured in an approximately straight line, or syzygy; that is, Earth and the body are in the same direction as seen from the Sun. Opposition occurs only for superior planets (see the diagram). The instant of opposition is defined as that when the apparent geocentric celestial longitude of the body differs by 180° from the apparent geocentric longitude of the Sun. At that time, a body is: The Moon, which orbits Earth rather than the Sun, is in approximate opposition to the Sun at full moon.

List of brightest stars

brightest starsbrightest starone of the brightest stars
The apparent visual magnitudes of the brightest stars can also be compared to non-stellar objects in our Solar System. Here the maximum visible magnitudes above the second brightest star, Sirius (−1.46), are as follows. Excluding the Sun, the brightest objects are the Moon (−12.7), Venus (−4.89), Jupiter (−2.94), Mars (−2.91), Mercury (−2.45), and Saturn (−0.49). Any exact order of the visual brightness of stars is not perfectly defined for four reasons: The source of magnitudes cited in this list is the linked Wikipedia articles—this basic list is a catalog of what Wikipedia itself documents. References can be found in the individual articles.


Meteoroid collisions with solid Solar System objects, including the Moon, Mercury, Callisto, Ganymede, and most small moons and asteroids, create impact craters, which are the dominant geographic features of many of those objects. On other planets and moons with active surface geological processes, such as Earth, Venus, Mars, Europa, Io, and Titan, visible impact craters may become eroded, buried, or transformed by tectonics over time. In early literature, before the significance of impact cratering was widely recognised, the terms cryptoexplosion or cryptovolcanic structure were often used to describe what are now recognised as impact-related features on Earth.

Astronomical naming conventions

formally designatednaming conventionalso written
H = Mercury (Hermes). V = Venus. E = Earth. M = Mars. J = Jupiter. S = Saturn. U = Uranus. N = Neptune. Jupiter trojans (minor planets that librate in 1:1 resonance with Jupiter) are named for characters of the legendary Trojan War. Asteroids at Lagrangian point are named after Greek characters (such as 588 Achilles), whilst asteroids at are named after Trojans (such as 884 Priamus). Trans-Jovian minor planets crossing or approaching the orbit of a giant planet, but not in a stabilizing resonance are named for centaurs (such as 2060 Chiron). Plutinos are named after mythological creatures associated with the underworld (such as 90482 Orcus).

List of Solar System extremes

largest object in the Solar System
This article describes extreme locations of the Solar System. Entries listed in bold are Solar System-wide extremes. * List of most distant trans-Neptunian objects * Extremes on Earth Solar System. Lists of geological features of the Solar System. List of gravitationally rounded objects of the Solar System. Yale-New Haven Teachers Institute, 07.03.03: "Voyage to the Planets" by Nicholas R. Perrone, 2007 (accessed November 2010). Journey Through the Galaxy: "Planets of the Solar System" by Stuart Robbins and David McDonald, 2006 (accessed November 2010). The Nine 8 Planets, "Appendix 2: Solar System Extrema" by Bill Arnett, 2007 (accessed November 2010).

Moment of inertia factor

moment of inertiamoment of inertia parameters
The Sun has by far the lowest moment of inertia factor value among Solar System bodies; it has by far the highest central density (162 g/cm3, compared to ~13 for Earth ) and a relatively low average density (1.41 g/cm 3 versus 5.5 for Earth). Saturn has the lowest value among the gas giants in part because it has the lowest bulk density (0.687 g/cm3). Ganymede has the lowest moment of inertia factor among solid bodies in the Solar System because of its fully differentiated interior, a result in part of tidal heating due to the Laplace resonance, as well as its substantial component of low density water ice.

Voyager 2

2Voyager IIMariner 12
Part of the Voyager program, it was launched 16 days before its twin, Voyager 1, on a trajectory that took longer to reach Jupiter and Saturn but enabled further encounters with Uranus and Neptune. It is the only spacecraft to have visited either of these two ice giant planets. Voyager 2 is the fourth of five spacecraft to achieve the Solar escape velocity, which will allow it to leave the Solar System. Its primary mission ended with the exploration of the Neptunian system on October 2, 1989, after having visited the Uranian system in 1986, the Saturnian system in 1981, and the Jovian system in 1979.

Voyager 1

Voyager IVoyagerMariner 11
Because of the greater photographic resolution allowed by a closer approach, most observations of the moons, rings, magnetic fields, and the radiation belt environment of the Jovian system were made during the 48-hour period that bracketed the closest approach. Voyager 1 finished photographing the Jovian system in April 1979. Discovery of ongoing volcanic activity on the moon Io was probably the greatest surprise. It was the first time active volcanoes had been seen on another body in the Solar System. It appears that activity on Io affects the entire Jovian system.

Titan (moon)

TitanSaturn's moon Titanatmosphere
Titan is the largest moon of Saturn and the second-largest natural satellite in the Solar System. It is the only moon known to have a dense atmosphere, and the only known body in space, other than Earth, where clear evidence of stable bodies of surface liquid has been found. Titan is the sixth gravitationally rounded moon from Saturn. Frequently described as a planet-like moon, Titan is 50% larger than Earth's moon and 80% more massive. It is the second-largest moon in the Solar System after Jupiter's moon Ganymede, and is larger than the planet Mercury, but only 40% as massive.


planetesimalsasteroid impactsplanetessimal
Many planetesimals eventually break apart during violent collisions, as may have happened to 4 Vesta and 90 Antiope, but a few of the largest planetesimals may survive such encounters and continue to grow into protoplanets and later planets. It is generally thought that about 3.8 billion years ago, after a period known as the Late Heavy Bombardment, most of the planetesimals within the Solar System had either been ejected from the Solar System entirely, into distant eccentric orbits such as the Oort cloud, or had collided with larger objects due to the regular gravitational nudges from the giant planets (particularly Jupiter and Neptune).

Centaur (small Solar System body)

centaurcentaursCentaur (minor planet)
Some Centaurs will evolve into Jupiter-crossing orbits whereupon their perihelia may become reduced into the inner Solar System and they may be reclassified as active comets in the Jupiter family if they display cometary activity. Centaurs will thus ultimately collide with the Sun or a planet or else they may be ejected into interstellar space after a close approach to one of the planets, particularly Jupiter. The relatively small size of Centaurs precludes remote observation of surfaces, but colour indices and spectra can provide clues about surface composition and insight into the origin of the bodies.


barycentrebarycentricbarycentric coordinates
If Jupiter had Mercury's orbit (57900000 km), the Sun–Jupiter barycenter would be approximately 55,000 km from the center of the Sun (r 1⁄R 1 ≈ 0.08). But even if the Earth had Eris' orbit (68 AU), the Sun–Earth barycenter would still be within the Sun (just over 30,000 km from the center). To calculate the actual motion of the Sun, only the motions of the four giant planets (Jupiter, Saturn, Uranus, Neptune) need to be considered. The contributions of all other planets, dwarf planets, etc. are negligible.