# Solar System Objects A working inventory of the solar system and the larger structure it sits in. This is a knowledge-base starter, not a complete catalog of every known asteroid or comet — there are more than a million cataloged small bodies. Named planets, dwarf planets, and moons are listed; for the large populations, the note gives official counts and the notable named members. **As of:** 11 November 2026 (America/Chicago), unless a section gives a more specific date. Use the `[[wikilinks]]` on major names to grow this folder into individual notes later. Those target notes are not created here. ## Contents - [[#Snapshot|Snapshot]] - [[#The Sun|The Sun]] - [[#The planets|The planets]] - [[#Moons by planet|Moons by planet]] - [[#Asteroids and small bodies|Asteroids and small bodies]] - [[#Dwarf planets|Dwarf planets]] - [[#Trans-Neptunian region|Trans-Neptunian region]] - [[#The Oort cloud|The Oort cloud]] - [[#The larger context|The larger context]] - [[#Sources|Sources]] - [[#Unverified or incomplete counts|Unverified or incomplete counts]] ## Snapshot | Population | Count | As of | Source | | --- | ---: | --- | --- | | [[Sun]] | 1 | — | — | | Planets (IAU) | 8 | 2006 definition, still current | IAU Resolution B5; NASA | | IAU dwarf planets | 5 | current | IAU / NASA | | Planetary satellites (includes Earth's Moon and [[Pluto]]'s five) | 461 | 11 Nov 2026 | JPL SSD body count; NASA, Oct 2026 | | Asteroids in the JPL Small-Body Database (includes KBOs, TNOs, and dwarf planets) | 1,580,277 | 11 Nov 2026, 5:07 PM CT | JPL SSD | | — numbered / unnumbered | 895,910 / 684,367 | same | JPL SSD | | Comets in the JPL SBDB (includes fragments) | 4,088 | same | JPL SSD | | — excluding fragments | 3,917 | same | JPL SBDB Query API | | Near-Earth objects (NEAs + NE comets) | 43,202 | 11 Nov 2026 | NASA CNEOS | | Small bodies with at least one known moon | 511 | 11 Nov 2026 | JPL SBDB Query API | JPL's 461 planetary satellites break down as: [[Earth]] 1, [[Mars]] 2, [[Jupiter]] 115, [[Saturn]] 293, [[Uranus]] 29, [[Neptune]] 16, and [[Pluto]] 5. Mercury and Venus have none. That sum is 461. ## The Sun [[Sun]] is a G2 V (yellow dwarf) main-sequence star at the center of the solar system. It accounts for about 99.8% of the system's mass and supplies the light, heat, and solar wind that define the heliosphere. | Property | Value | Source | | --- | --- | --- | | Spectral type | G2 V | NSSDCA Sun Fact Sheet (updated 9 May 2024) | | Mass | 1.9884 × 10³⁰ kg (about 332,900 Earth masses) | same | | Volumetric mean radius | 695,700 km (diameter 1,391,400 km) | same | | Effective temperature | 5,772 K | same | | Luminosity | 3.828 × 10²⁶ W | same (382.8 × 10²⁴ J/s) | | Absolute magnitude | +4.83 | same | | Mean distance from Earth | 149.6 million km (1 au) | same | The eight planets, the dwarf planets, and the small-body populations all orbit the Sun. Beyond the planets, the Sun's influence continues as the [[heliosphere]], out to the [[heliopause]]. ## The planets The IAU (2006) defines a planet in the solar system as a body that orbits the Sun, is nearly round due to its own gravity, and has cleared the neighborhood around its orbit. That definition recognizes eight planets. Distances and diameters below are from the NASA / NSSDCA Planetary Fact Sheet (metric; last updated 18 March 2025). Distances in au use the fact sheet's own mean Earth–Sun distance of 149.6 million km. Moon counts on that fact sheet are outdated; the moon column here uses the November 2026 IAU / NASA / JPL totals discussed above. | Planet | Type | Mean distance | Diameter | Moons | | --- | --- | ---: | ---: | ---: | | [[Mercury]] | Terrestrial | 0.387 au (57.9 million km) | 4,879 km | 0 | | [[Venus]] | Terrestrial | 0.723 au (108.2 million km) | 12,104 km | 0 | | [[Earth]] | Terrestrial | 1.000 au (149.6 million km) | 12,756 km | 1 | | [[Mars]] | Terrestrial | 1.524 au (228.0 million km) | 6,792 km | 2 | | [[Jupiter]] | Gas giant | 5.204 au (778.5 million km) | 142,984 km | 115 | | [[Saturn]] | Gas giant | 9.572 au (1,432.0 million km) | 120,536 km | 293 | | [[Uranus]] | Ice giant | 19.164 au (2,867.0 million km) | 51,118 km | 29 | | [[Neptune]] | Ice giant | 30.181 au (4,515.0 million km) | 49,528 km | 16 | [[Mercury]] through [[Mars]] are the inner, rocky (terrestrial) planets. [[Jupiter]] and [[Saturn]] are gas giants with extensive ring and moon systems. [[Uranus]] and [[Neptune]] are ice giants. All four giant planets have rings; the terrestrial planets do not. ## Moons by planet NASA and JPL reported **461 officially recognized moons orbiting planets**, including [[Pluto]]'s five, as of October 2026, and JPL's body-count file still showed 461 on 11 November 2026. Hundreds more moons orbit asteroids, dwarf planets other than Pluto, and other trans-Neptunian objects; those are noted under dwarf planets and small bodies rather than in this 461-count. Provisional or still-unnamed moons are given as counts, not full designation lists. ### Earth [[Earth]] has one moon. - [[Moon|The Moon]] (Luna). Diameter 3,475 km (NSSDCA fact sheet). Mean distance from Earth 384,000 km. The only satellite from which humans have returned samples (Apollo, 1969–1972). ### Mars [[Mars]] has two small, irregular moons, both likely captured: - [[Phobos]] — the inner and larger moon; slowly spiraling inward. - [[Deimos]] — the outer moon. ### Jupiter [[Jupiter]] has **115** moons officially recognized by the IAU (NASA Jupiter moons page). NASA's all-moons table lists **57 named** moons and many provisionally designated ones; the remaining official moons are provisionally designated and are not all yet on that table (57 named + 58 unnamed or provisional = 115). Irregular-group membership is dynamical and is still being refined; a few objects sit on the edges of groups. #### Inner regular moons (Amalthea group) [[Metis]], [[Adrastea]], [[Amalthea]], [[Thebe]] #### Galilean moons Discovered by Galileo in 1610; the four largest moons in the Jovian system, and among the most important worlds in the solar system. - [[Io]] — most volcanically active body in the solar system - [[Europa]] — ice shell over a subsurface ocean; target of NASA's Europa Clipper - [[Ganymede]] — largest moon in the solar system, larger than Mercury; own magnetic field - [[Callisto]] — most heavily cratered of the four; possible subsurface ocean #### Prograde irregular moons - Isolated: [[Themisto]] - Himalia group: [[Leda]], [[Himalia]], [[Lysithea]], [[Elara]], [[Dia]], [[Pandia]], [[Ersa]] - Isolated: [[Carpo]] - Isolated (unusual prograde orbit among retrograde moons): [[Valetudo]] #### Retrograde irregular moons These are grouped by similar orbits (inclination, eccentricity, semimajor axis). Named members commonly assigned as follows: - **Ananke group:** [[Euporie]], [[Thelxinoe]], [[Euanthe]], [[Helike]], [[Orthosie]], [[Iocaste]], [[Praxidike]], [[Harpalyke]], [[Mneme]], [[Hermippe]], [[Thyone]], [[Ananke]], [[Philophrosyne]], [[Eupheme]] - **Carme group:** [[Taygete]], [[Isonoe]], [[Pasithee]], [[Chaldene]], [[Kale]], [[Erinome]], [[Aitne]], [[Kalyke]], [[Carme]], [[Eukelade]], [[Arche]], [[Kallichore]], [[Herse]] - **Pasiphae group:** [[Eurydome]], [[Autonoe]], [[Sponde]], [[Pasiphae]], [[Megaclite]], [[Sinope]], [[Callirrhoe]], [[Hegemone]], [[Aoede]], [[Cyllene]], [[Kore]], [[Eirene]] **Unnamed / provisional:** 58 official moons are not yet named. NASA's table includes numbered but unnamed satellites (for example S/2010 J1, S/2011 J1, S/2017 J2–J9) plus later provisional designations such as S/2021 J1–J6, S/2022 J1–J3, and S/2024 J1. ### Saturn [[Saturn]] has **293 confirmed moons as of August 2026**, the most of any planet (NASA Saturn moons page). The list below gives every **named** moon from that page, grouped by dynamical family. Four numbered moons on the same table still lack names (S/2004 S7, S/2004 S26, S/2004 S29, S/2004 S34). The rest of the 293 are provisionally designated. **Named moons: 63. Provisionally designated or unnamed: 230.** #### Ring moons and shepherds [[Pan]], [[Daphnis]], [[Atlas]], [[Prometheus]], [[Pandora]], [[Aegaeon]] (plus the still-unnamed ring moonlet S/2009 S1) #### Co-orbitals [[Janus]], [[Epimetheus]] — share a closely related orbit and periodically exchange places. #### Alkyonides [[Methone]], [[Anthe]], [[Pallene]] — small moons between Mimas and Enceladus. #### Major inner icy moons (and their trojans) - [[Mimas]] - [[Enceladus]] — global subsurface ocean; south-polar plumes - [[Tethys]], with trojan moons [[Telesto]] and [[Calypso]] - [[Dione]], with trojan moons [[Helene]] and [[Polydeuces]] - [[Rhea]] #### Outer large moons - [[Titan]] — second-largest moon in the solar system; thick nitrogen atmosphere; surface lakes of methane and ethane; subsurface ocean - [[Hyperion]] — irregular, chaotically rotating - [[Iapetus]] — two-tone leading and trailing hemispheres; equatorial ridge #### Inuit group (prograde irregular) [[Kiviuq]], [[Ijiraq]], [[Paaliaq]], [[Siarnaq]], [[Tarqeq]] #### Gallic group (prograde irregular) [[Albiorix]], [[Bebhionn]], [[Erriapus]], [[Tarvos]] #### Norse group (retrograde irregular) Includes [[Phoebe]], Saturn's largest irregular moon and a likely captured body. [[Phoebe]], [[Ymir]], [[Suttungr]], [[Mundilfari]], [[Skathi]], [[Thrymr]], [[Narvi]], [[Aegir]], [[Bergelmir]], [[Bestla]], [[Farbauti]], [[Fenrir]], [[Fornjot]], [[Hati]], [[Hyrrokkin]], [[Kari]], [[Loge]], [[Skoll]], [[Surtur]], [[Jarnsaxa]], [[Greip]], [[Gridr]], [[Angrboda]], [[Skrymir]], [[Gerd]], [[Eggther]], [[Beli]], [[Gunnlod]], [[Thiazzi]], [[Alvaldi]], [[Geirrod]] ### Uranus [[Uranus]] has **29 known moons as of August 2026** (NASA). Five are large and roughly spherical; 13 small inner moons are associated with the ring system; 9 named irregulars lie far out; two recent discoveries are still provisionally designated. Uranian moons are named for characters from Shakespeare and Alexander Pope. #### Inner (ring-region) moons [[Cordelia]], [[Ophelia]], [[Bianca]], [[Cressida]], [[Desdemona]], [[Juliet]], [[Portia]], [[Rosalind]], [[Cupid]], [[Belinda]], [[Perdita]], [[Puck]], [[Mab]] #### Five major moons | Moon | Diameter | Notes | | --- | ---: | --- | | [[Miranda]] | 472 km | Deep canyons and jumbled terrain | | [[Ariel]] | 1,158 km | Bright, relatively young surface | | [[Umbriel]] | 1,169 km | Dark, ancient, heavily cratered | | [[Titania]] | 1,578 km | Largest Uranian moon | | [[Oberon]] | 1,523 km | Outermost of the five majors | Diameters from JPL Solar System Dynamics, as quoted by NASA. #### Irregular outer moons (named) [[Francisco]], [[Caliban]], [[Stephano]], [[Trinculo]], [[Sycorax]], [[Margaret]], [[Prospero]], [[Setebos]], [[Ferdinand]] #### Provisional S/2023 U1 and S/2025 U1 (2 moons). ### Neptune [[Neptune]] has **16 officially recognized moons**. Fourteen are named for Greek sea gods and nymphs; two remain provisional. [[Triton]] is the dominant moon — comparable in size to [[Pluto]], with a retrograde (backward) orbit, almost certainly a captured Kuiper-belt object. It accounts for nearly all of the mass in Neptune's satellite system. #### Inner regular moons [[Naiad]], [[Thalassa]], [[Despina]], [[Galatea]], [[Larissa]], [[Hippocamp]], [[Proteus]] #### Captured retrograde moon [[Triton]] #### Irregular outer moons (named) [[Nereid]], [[Halimede]], [[Sao]], [[Laomedeia]], [[Psamathe]], [[Neso]] #### Provisional S/2002 N5 and S/2021 N1 (2 moons). ## Asteroids and small bodies The IAU groups everything that is not a planet, dwarf planet, or satellite as **small solar system bodies**. JPL's Small-Body Database is the practical catalog. On 11 November 2026 it held **1,580,277** asteroids (including trans-Neptunian objects and the dwarf planets, which are also numbered minor planets) and **4,088** comets including fragments. The tables below use JPL **orbit classes**, which are cuts in orbital elements, not always the same as a dynamically confirmed family. Definitions are JPL's. ### Main belt The main asteroid belt lies between [[Mars]] and [[Jupiter]]. JPL splits it into inner, main, and outer belts by semimajor axis. | JPL class | Definition | Count (11 Nov 2026) | | --- | --- | ---: | | Inner main-belt (IMB) | a < 2.0 au, q > 1.666 au | 33,186 | | Main-belt (MBA) | 2.0 au < a < 3.2 au, q > 1.666 au | 1,396,376 | | Outer main-belt (OMB) | 3.2 au < a < 4.6 au | 51,047 | | Mars-crossing (MCA) | 1.3 au < q < 1.666 au, a < 3.2 au | 30,568 | The inner-belt class includes the Hungaria region. The outer-belt class includes the Cybele region and the [[Hildas]] (see below). Many smaller dynamical **families** — fragments of ancient collisions — sit inside these classes. Well-known families include Flora, Vesta, Eunomia, Koronis, Eos, Themis, Nysa–Polana, Phocaea, and Baptistina. This note does not attempt current membership counts for those families. #### Notable large main-belt bodies Diameters and semimajor axes from the JPL Small-Body Database lookup (11 Nov 2026). [[Ceres]] is also an IAU dwarf planet and is cross-listed in that section. | Object | Class | a (au) | Diameter (km) | Notes | | --- | --- | ---: | ---: | --- | | [[Ceres]] (1) | MBA | 2.77 | 939.4 | Only inner-solar-system dwarf planet; no moons; visited by Dawn | | [[Vesta]] (4) | MBA | 2.36 | 522.8 | Second-most massive belt object; Dawn orbiter; vestoid family | | [[Pallas]] (2) | MBA | 2.77 | 513 | Highly inclined; one of the first asteroids discovered (1802) | | [[Hygiea]] (10) | MBA | 3.15 | 407.1 | Fourth-largest by diameter; Hygiea family | | [[Interamnia]] (704) | MBA | 3.06 | 306.3 | | | [[52 Europa]] | MBA | 3.09 | 303.9 | Not the Jovian moon | | [[Davida]] (511) | MBA | 3.16 | 270.3 | | | [[Sylvia]] (87) | OMB | 3.49 | 253.1 | Has two moons, Romulus and Remus | | [[Psyche]] (16) | MBA | 2.93 | 222 | Metal-rich; target of NASA's Psyche mission | ### Near-Earth objects Near-Earth objects (NEOs) have perihelia within 1.3 au. NASA CNEOS discovery statistics, latest row **11 November 2026**: | Group | Count | Definition (CNEOS / JPL) | | --- | ---: | --- | | Near-Earth asteroids (NEAs) | 43,077 | All NEO asteroids | | — [[Atira]] group (Atiras) | 41 | Orbits entirely inside Earth's (Q < 0.983 au); also called Interior Earth Objects | | — [[Aten]] group (Atens) | 3,535 | a < 1.0 au, Q > 0.983 au | | — [[Apollo]] group (Apollos) | 24,549 | a > 1.0 au, q < 1.017 au; Earth-crossing | | — [[Amor]] group (Amors) | 14,952 | 1.017 au < q < 1.3 au | | NEAs ≳ 140 m | 11,707 | Size estimated from absolute magnitude | | NEAs ≳ 1 km | 884 | | | Potentially hazardous asteroids (PHAs) | 2,533 | NEAs that can approach Earth closely and are large enough to cause significant damage | | — PHAs ≳ 1 km | 156 | | | Near-Earth comets (NECs) | 125 | Fragmented comets counted once for the parent | | **All NEOs** | **43,202** | NEAs + NECs | JPL's orbit-class counts on the same day are very close but not identical (IEO/Atira 39, Aten 3,510, Apollo 24,486, Amor 14,998), because CNEOS and the SBDB class cuts can differ slightly in timing and definition. The table above is the CNEOS discovery census. #### Notable near-Earth objects | Object | Group | Notes | | --- | --- | --- | | [[Eros]] (433) | Amor | First NEA discovered (1898); orbited by NEAR Shoemaker | | [[Itokawa]] (25143) | Apollo | Hayabusa sample return | | [[Ryugu]] (162173) | Apollo | Hayabusa2 sample return | | [[Bennu]] (101955) | Apollo | OSIRIS-REx sample return | | [[Apophis]] (99942) | Aten | Closely watched PHA; 2029 Earth flyby | | [[Phaethon]] (3200) | Apollo | Parent of the Geminid meteor shower | | [[Toutatis]] (4179) | Apollo | Elongated, tumbling; Chang'e 2 flyby | | 2010 TK7 (706765) | Aten | Confirmed [[Earth]] trojan (see Trojans) | ### Trojans Trojans share a planet's orbit, librating around the L4 (60° ahead) or L5 (60° behind) Lagrange points. By convention, Jupiter's L4 swarm is the **Greek camp** and L5 is the **Trojan camp** (a few names fall on the "wrong" side; [[Hektor]], for example, is a Greek hero in the L4 camp). The IAU Minor Planet Center's official Trojan lists were last updated **30 May 2026**. For Earth, Mars, and Uranus, MPC lists only objects confirmed as trojans by long-term integrations. Jupiter and Neptune lists use cuts in osculating elements and are "not 100 percent reliable," in MPC's words. | Planet | MPC confirmed / listed trojans (30 May 2026) | Notes | | --- | ---: | --- | | [[Earth]] | 1 | [[2010 TK7]] (now numbered 706765), at L4. Diameter about 0.38 km (JPL). | | [[Mars]] | 18 | First was [[Eureka]] (5261), at L5. Most known Martian trojans are in the L5 Eureka family; a few occupy L4. | | [[Jupiter]] | 15,765 | L4 (Greek camp) 9,823; L5 (Trojan camp) 5,942. See notable members below. | | [[Uranus]] | 0 | No object currently meets MPC's long-term confirmation cut. Temporary co-orbitals have been discussed (for example 2011 QF99); JPL classifies 2011 QF99 as a centaur, not a confirmed Uranus trojan. | | [[Neptune]] | 35 | Includes named objects [[Otrera]] (385571) and [[Clete]] (385695), and the early discovery 2001 QR322. Most known members are at L4. | | **Total** | **15,819** | | JPL's **TJN** orbit class (4.6 au < a < 5.5 au, e < 0.3) counted **16,472** objects on 11 November 2026. That is a broader element cut than MPC's official Jupiter-trojan list, so the two numbers should not be used interchangeably. #### Notable Jupiter trojans Diameters from JPL SBDB (11 Nov 2026). NASA's Lucy mission is en route to several of these (arrival at the L4 cloud in 2027). | Object | Camp | Diameter (km) | Notes | | --- | --- | ---: | --- | | [[Achilles]] (588) | L4 Greek | 130 | First Jupiter trojan discovered (1906) | | [[Patroclus]] (617) | L5 Trojan | 140 | Binary with Menoetius; Lucy target | | [[Hektor]] (624) | L4 Greek | 225 | Largest Jupiter trojan; elongated, has a moon (Skamandrios) | | [[Nestor]] (659) | L4 | — | Early discovery (1908) | | [[Priamus]] (884) | L5 | — | | | [[Agamemnon]] (911) | L4 | — | | | [[Odysseus]] (1143) | L4 | — | | ### Hildas [[Hildas]] are asteroids in the **3:2 mean-motion resonance** with [[Jupiter]], typically near a ≈ 4.0 au, inward of the Jupiter trojans and outward of the main belt proper. They fall inside JPL's outer main-belt (OMB) class (51,047 objects with 3.2 au < a < 4.6 au), which also includes non-Hilda populations such as the Cybeles. The namesake is [[Hilda]] (153): a = 3.97 au, diameter 171 km (JPL). Other well-known members include 190 Ismene and 334 Chicago. A current, official Hilda-only census (resonance-confirmed, not just an element box) was not verified for this note. See [[#Unverified or incomplete counts]]. ### Centaurs [[Centaurs]] have orbits between Jupiter and Neptune. JPL's CEN class is defined as 5.5 au < a < 30.1 au and counted **1,088** objects on 11 November 2026. The class mixes icy small bodies, some of which show comet-like activity, and it can include objects other catalogs treat as inner scattered-disk bodies. | Object | a (au) | Diameter (km) | Notes | | --- | ---: | ---: | --- | | [[Chiron]] (2060) | 13.7 | 166 | First recognized centaur (1977); sometimes active, comet designation 95P/Chiron | | [[Chariklo]] (10199) | 15.7 | 302 | Largest known centaur; has a ring system | | [[Pholus]] (5145) | 20.3 | 190 | Very red surface | ### Comets JPL counted **4,088** comets including fragments, or **3,917** excluding fragments, on 11 November 2026. JPL assigns each object a single orbit class, so the classical period classes and the Tisserand-parameter classes do not add to the same total and should not be summed naively. | JPL class | Definition | Count (11 Nov 2026) | | --- | --- | ---: | | Jupiter-family, Levison–Duncan (JFc) | 2 < T_J < 3 | 835 | | Encke-type (ETc) | T_J > 3 and a < a_Jupiter | 80 | | Chiron-type (CTc) | T_J > 3 and a > a_Jupiter | 22 | | Jupiter-family, classical (JFC) | Period P < 20 yr, and not placed in another class | 17 | | Halley-type, classical (HTC) | 20 yr < P < 200 yr | 112 | | Parabolic (PAR) | e = 1.0 | 1,763 | | Hyperbolic (HYP) | e > 1.0 | 520 | Most short-period, Jupiter-family comets appear under **JFc**. The small classical **JFC** count is a residual class, not the full Jupiter-family population. Long-period and dynamically new comets from the [[Oort cloud]] are largely in the parabolic and hyperbolic classes (some hyperbolic comets are interstellar; see below). Near-Earth comets: 125 (CNEOS, 11 Nov 2026). #### Notable comets - **Short-period / Jupiter-family:** 2P/[[Encke]] (unusually short period), 9P/Tempel, 67P/[[Churyumov–Gerasimenko]] (Rosetta), 81P/Wild, 103P/Hartley - **Halley-type:** 1P/[[Halley]] (the archetype; period about 76 years), 109P/Swift–Tuttle (Perseid parent), 12P/Pons–Brooks - **Long-period / "great" comets:** C/1995 O1 (Hale–Bopp), C/2020 F3 (NEOWISE), C/2023 A3 (Tsuchinshan–ATLAS) ### Interstellar objects Three interstellar objects have been discovered passing through the solar system. They are not bound to the Sun (eccentricity > 1, negative semimajor axis). | Object | Official designations | JPL class | a (au) | Notes | | --- | --- | --- | ---: | --- | | [[ʻOumuamua]] | 1I/ʻOumuamua, A/2017 U1 | HYA (hyperbolic asteroid) | −1.27 | First known interstellar object (2017); no coma observed | | [[Borisov]] | 2I/Borisov, C/2019 Q4 (Borisov) | HYP | −0.851 | First clearly active interstellar comet (2019) | | [[3I/ATLAS]] | 3I/ATLAS, C/2025 N1 (ATLAS) | HYP | −0.264 | Third interstellar object; designated by the MPC on 2 July 2025 | ### Small-body moons The Galileo flyby of asteroid [[Ida]] in 1993 revealed its moon [[Dactyl]] and showed that small bodies can have satellites. JPL's SBDB flagged **511** small bodies with at least one known moon as of 11 November 2026. These include moons of asteroids (for example Ida/Dactyl, Sylvia/Romulus and Remus), and moons of trans-Neptunian objects and dwarf-planet candidates listed in the next section. NASA notes that hundreds of such moons have been confirmed. ## Dwarf planets The IAU (2006) defines a [[dwarf planet]] as a body that orbits the Sun, is nearly round, has **not** cleared its orbital neighborhood, and is not a satellite. The IAU has formally recognized five. NASA and the IAU both note that many more may exist, especially among the large trans-Neptunian objects. ### The five IAU dwarf planets Listed here in order of increasing semimajor axis. Axes for the four trans-Neptunian dwarf planets are from JPL SBDB (11 Nov 2026). Diameters for Ceres are from JPL; Pluto's is from the NSSDCA fact sheet; Haumea, Makemake, and Eris diameters are the NASA dwarf-planet pages' rounded figures. | Dwarf planet | Region | a (au) | Diameter | Moons | | --- | --- | ---: | --- | --- | | [[Ceres]] (1) | Main belt | 2.77 | 939.4 km (JPL) | none | | [[Pluto]] (134340) | Kuiper belt (3:2 resonant, a plutino) | 39.6 | 2,376 km (NSSDCA) | 5 — [[Charon]], [[Styx]], [[Nix]], [[Kerberos]], [[Hydra]] | | [[Haumea]] (136108) | Kuiper belt | 43.1 | about 1,740 km equatorial (NASA) | 2 — [[Hiʻiaka]], [[Namaka]]; also a ring | | [[Makemake]] (136472) | Kuiper belt | 45.6 | about 1,430 km (NASA) | 1 provisional — S/2015 (136472) 1, nickname MK 2 | | [[Eris]] (136199) | Scattered disc | 67.9 | about 2,400 km (NASA) | 1 — [[Dysnomia]] | [[Charon]] is so large relative to Pluto (about half the diameter) that the two are often described as a binary system, with the barycenter outside Pluto. The four smaller Plutonian moons orbit that pair. Ceres is the only dwarf planet in the inner solar system and is listed again under the main belt. ### Widely accepted candidates These objects are widely regarded as dwarf-planet candidates (or, by many planetary scientists, as dwarf planets in all but formal IAU recognition) because of their size and inferred hydrostatic equilibrium. They are **not** among the IAU's five. Semimajor axes from JPL SBDB, 11 Nov 2026. | Object | a (au) | Class / region | Known moons / notes | | --- | ---: | --- | --- | | [[Orcus]] (90482) | 39.4 | Plutino (3:2) | [[Vanth]] | | [[Salacia]] (120347) | 42.1 | Classical / resonant Kuiper belt | [[Actaea]] | | [[Quaoar]] (50000) | 43.2 | Classical Kuiper belt | [[Weywot]]; also a ring system | | [[Varuna]] (20000) | 43.2 | Classical Kuiper belt | Diameter 900 km (JPL); no confirmed moon in the lookup | | [[Máni]] (307261, 2002 MS4) | 41.6 | Kuiper belt | Large, poorly studied; no moon in the JPL lookup | | [[Ixion]] (28978) | 39.3 | Plutino | | | [[Gonggong]] (225088) | 66.9 | Scattered disc | [[Xiangliu]] | | [[Sedna]] (90377) | 544 | Detached / sednoid | Extreme orbit; no known moon | Other large TNOs are sometimes discussed in the same breath; the list above is the usual core set, not an official IAU roster. ## Trans-Neptunian region A trans-Neptunian object (TNO) has a semimajor axis beyond Neptune (JPL: a > 30.1 au). JPL counted **8,338** TNOs on 11 November 2026. That total includes the trans-Neptunian dwarf planets and candidates. The region is usually divided by dynamics, not just distance. ### Kuiper belt The [[Kuiper belt]] is a torus of icy bodies beginning just beyond [[Neptune]] (about 30 au) and extending to roughly 50 au. It is the source region of many short-period, Jupiter-family comets' ancestors (via the scattered disc and centaur pathway) and the home of [[Pluto]]. Common dynamical groups: - **Classical Kuiper belt objects (cubewanos).** Low-eccentricity orbits not in a major mean-motion resonance with Neptune. Named after 1992 QB1 (now 15760 Albion), the first Kuiper-belt object found after Pluto. Includes [[Makemake]], [[Quaoar]], [[Varuna]], and [[Arrokoth]] (486958, 2014 MU69) — the cold classical contact binary visited by New Horizons on 1 January 2019, the most distant object yet explored by a spacecraft. [[Arrokoth]] orbits at a = 44.1 au (JPL). - **Resonant objects / plutinos.** Locked in mean-motion resonances with Neptune. **Plutinos** occupy the 3:2 resonance, like [[Pluto]] itself; examples include [[Orcus]] and [[Ixion]]. **Twotinos** occupy the 1:2 resonance. Other resonances (2:5, 3:5, and so on) are also populated. - **Scattered disc.** Higher-eccentricity, often higher-inclination orbits still subject to Neptune's gravitational influence. [[Eris]] and [[Gonggong]] are the emblematic large members. Scattered-disc objects can have perihelia near Neptune and aphelia far beyond the classical belt. This note does not give separate official counts for classical, resonant, and scattered-disc objects. JPL's single TNO class does not split them, and the MPC public summary's subcategory fields were not usable (see [[#Unverified or incomplete counts]]). ### Detached objects and sednoids **Detached** TNOs have perihelia high enough that they are largely decoupled from Neptune. **Sednoids** are an extreme subset, with very distant perihelia and huge semimajor axes, typified by [[Sedna]]. | Object | a (au) | Notes | | --- | ---: | --- | | [[Sedna]] (90377) | 544 | Prototype sednoid; perihelion far beyond Neptune | | 2012 VP113 | 268 | Sometimes nicknamed "Biden"; another sednoid | | [[Leleākūhonua]] (541132, 2015 TG387) | 1,340 | Extremely distant sednoid | The unusual clustering of some of these extreme orbits is one of the observational arguments offered for a hypothetical additional planet. ### Planet Nine [[Planet Nine]] is a **hypothetical** planet proposed to explain the clustered orbital alignments of certain extreme trans-Neptunian objects (notably the argument advanced by Batygin and Brown in 2016). No such planet has been discovered. Surveys have steadily narrowed the sky where a distant giant planet could still hide, but the object remains unconfirmed. It should not be confused with [[Pluto]] (once called the ninth planet) or with any cataloged TNO. ## The Oort cloud The [[Oort cloud]] is a vast, roughly spherical reservoir of icy bodies inferred from the orbits of long-period comets. It has not been directly imaged as a structure; its existence is deduced from the incoming directions and nearly parabolic orbits of those comets. It is usually described in two parts: - **Inner Oort cloud, or Hills cloud** — a denser, more flattened inner region, typically placed at a few thousand to a few tens of thousands of au. - **Outer Oort cloud** — a more spherical halo extending outward toward the Sun's tidal boundary with the Galaxy, often quoted as on the order of 50,000–100,000 au or more. The cloud is the source of most long-period and "dynamically new" comets. Passing stars, galactic tides, and molecular clouds can perturb objects inward onto Sun-grazing or observable paths. Population estimates run to trillions of bodies, but those figures are model-dependent and are not an observational census. ## The larger context The solar system does not end at the last planet, and it does not sit in empty space. Outward from the Sun, the next well-established structures are these. ### Heliosphere and heliopause The [[heliosphere]] is the bubble blown into the interstellar medium by the solar wind. Inside it, the plasma is solar; outside, it is interstellar. The outer boundary is the [[heliopause]]. Inward of that boundary lies the termination shock, where the solar wind slows from supersonic to subsonic speeds. [[Voyager 1]] crossed the heliopause in August 2012 at about 122 au. [[Voyager 2]] crossed in November 2018 at about 119 au. Both spacecraft are now sampling the local interstellar medium while still feeling the Sun's gravity. The heliosphere is not a perfect sphere; its shape changes with the solar cycle and with the surrounding interstellar flow. ### Local Interstellar Cloud The Sun is currently traveling through the [[Local Interstellar Cloud]] (LIC), a modestly dense, partially ionized patch of interstellar gas inside a larger cavity. The LIC is the immediate galactic environment just outside the heliopause. ### Local Bubble The [[Local Bubble]] (or Local Hot Bubble) is a low-density cavity in the interstellar medium, hundreds of light-years across, in which the Sun and the Local Interstellar Cloud are embedded. It is thought to have been carved by stellar winds and supernova explosions over the past several million years. ### Orion Arm The solar system lies in the [[Orion Arm]] (also called the Orion–Cygnus Arm or Local Arm), a relatively minor spiral-arm structure of the [[Milky Way]], between the larger Sagittarius and Perseus arms. ### Milky Way The [[Milky Way]] is the barred spiral galaxy that contains the solar system. The Sun orbits well out from the center (on the order of 26,000 light-years), completing a circuit in roughly a quarter of a billion years. The galactic disk, bulge, halo, and central supermassive black hole ([[Sagittarius A*]]) are the galaxy's main structural parts. ### Local Group The [[Local Group]] is the galaxy group that includes the Milky Way, the Andromeda Galaxy (M31), the Triangulum Galaxy (M33), and several dozen smaller galaxies (the Magellanic Clouds among them). Andromeda and the Milky Way are the two dominant members and are approaching each other. ### Laniakea Supercluster The [[Laniakea Supercluster]] is the large-scale structure in which the Local Group is embedded, defined by the flow of galaxies toward a shared gravitational basin (associated with the Great Attractor region). The name, from Hawaiian *laniakea* ("immense heaven"), was introduced by Tully and colleagues in 2014. Laniakea includes what was traditionally called the Virgo Supercluster and spans hundreds of millions of light-years. Beyond Laniakea lie neighboring superclusters and the still-larger cosmic web of filaments, walls, and voids. That is the setting of the solar system, not part of the solar system itself. ## Sources Primary catalogs and official pages, consulted 11 November 2026: 1. NASA / JPL Solar System Dynamics body-count file, `https://ssd.jpl.nasa.gov/dat/body_count.json` — timestamp 2026-11-11 23:07:02 UTC (5:07 PM CT). Planets: 8; planetary satellites: 461; asteroids: 1,580,277 (895,910 numbered, 684,367 unnumbered); comets: 4,088 (610 numbered, 3,478 unnumbered). 2. NASA / JPL SBDB Query API, `https://ssd-api.jpl.nasa.gov/sbdb_query.api` — orbit-class counts and the 511 small bodies with satellites, queried 11 November 2026. Class definitions from the same API (`sb-defs=class`). 3. NASA / JPL SBDB Lookup API — physical parameters and semimajor axes for individual small bodies and dwarf planets, queried 11 November 2026. 4. NASA CNEOS Discovery Statistics, `https://cneos.jpl.nasa.gov/stats/numbers.json` — latest row dated 2026-11-11. CNEOS notes that the most recent date is the discovery date of the most recently discovered NEO. 5. IAU Minor Planet Center, Trojan Minor Planets, `https://www.minorplanetcenter.net/iau/lists/Trojans.html` and the Jupiter Trojan list — last updated 30 May 2026. 6. IAU Resolution B5 (2006), *Definition of a Planet in the Solar System*, and Resolution B6 on Pluto. 7. NASA, "About the Planets," `https://science.nasa.gov/solar-system/planets/` — eight planets and five official dwarf planets. 8. NASA, "Moons: Facts," `https://science.nasa.gov/solar-system/moons/facts/` — 461 official planetary moons as of October 2026, including Pluto's five. 9. NASA Jupiter moons, `https://science.nasa.gov/jupiter/moons` — 115 IAU-recognized moons; named list from `https://science.nasa.gov/jupiter/jupiter-moons/all-jupiter-moons/`. 10. NASA Saturn moons, `https://science.nasa.gov/saturn/moons/` — 293 confirmed moons as of August 2026, and the named/provisional table used above. 11. NASA, "Uranus Moons: Facts," `https://science.nasa.gov/uranus/moons/facts/` — 29 moons as of August 2026; major-moon diameters from JPL as quoted there. 12. NASA Neptune moons, `https://science.nasa.gov/neptune/moons/` — 16 official moons and the named/provisional table. 13. NASA / NSSDCA Planetary Fact Sheet (metric), `https://nssdc.gsfc.nasa.gov/planetary/factsheet/` — last updated 18 March 2025. Used for planetary distances and diameters only; its moon counts are older than the 2026 NASA/JPL totals. 14. NASA / NSSDCA Sun Fact Sheet, `https://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html` — last updated 9 May 2024. 15. NASA dwarf planet pages, `https://science.nasa.gov/dwarf-planets/` — official five, rounded sizes, and moons (including Makemake's provisional MK 2). 16. NASA, "Comet 3I/ATLAS," and MPC MPEC 2025-N12 — official designation 3I/ATLAS = C/2025 N1 (ATLAS). 17. NASA Voyager Interstellar Mission, `https://science.nasa.gov/mission/voyager/interstellar-mission/` — Voyager 1 and 2 heliopause crossings. 18. Tully, R. B., et al. (2014), "The Laniakea supercluster of galaxies," *Nature* — naming and definition of Laniakea. ## Unverified or incomplete counts These are deliberately not stated as hard official totals in the sections above. - **Hilda population.** No current resonance-confirmed Hilda census from JPL or a dated MPC Hilda list was verified. MPC's public "Census of Dwarf/Minor Planets" displayed a Hilda number, but the same table showed unusable zeros for plutinos and classical TNOs, so that census was not trusted here. - **Kuiper-belt subtypes.** No reliable official split of the 8,338 JPL TNOs into classical (cubewano), resonant (plutino, twotino, and others), scattered-disc, and detached counts was obtained. - **Jupiter moons table completeness.** NASA's all-Jupiter-moons table lists 57 named moons plus 39 provisional designations (96 rows). The official IAU-recognized total is 115, so 19 official moons are not yet on that table. They are included in the 58 unnamed/provisional count, not listed individually. - **Saturn family assignments for unnamed moons.** The 230 provisionally designated Saturn moons are not sorted into Inuit, Gallic, or Norse groups here. - **Uranus and Neptune temporary co-orbitals** beyond what MPC lists as confirmed trojans (zero for Uranus, 35 for Neptune as of 30 May 2026). - **Oort-cloud population and exact boundaries.** These remain model-dependent inferences, not a catalog count. - **Planet Nine.** Undiscovered; no mass, orbit, or existence is confirmed. Small-body discovery is ongoing. The snapshot counts will be out of date quickly; the JPL body-count file, the SBDB Query API, CNEOS totals, and the MPC Trojan lists are the places to refresh them.