[[caption-width-right:350:[[MyFriendsAndZoidberg Ignore Pluto. It's not a planet anymore.]] Also, [[YouCannotGraspTheTrueForm Definitely not to Scale]]]]

The things you can find in our star system. Generally speaking, it consists of a central star, four Earth-type planets, four gas giants, and a large amount of smaller objects, including dwarf planets, moons, asteroids, comets and space junk, mostly clustered in rings around the Sun or other planets.

If you're interested in things in space farther away than our star system, you might wish to consult UsefulNotes/LocalStars. If you're interested in what planets might, or might not, be orbiting other stars, you might wish to consult the more general Useful Notes page on UsefulNotes/{{Planets}}.

* UsefulNotes/TheSun: The star of the show, literally and figuratively. About 99.9% of all the mass in the Solar system is in the sun.
** See {{Heliotropes}} for related tropes.


Most of these and their associated moons are named after characters from Myth/ClassicalMythology; the planets themselves have Roman/Latin names, but the moons are more variable.

!!Terrestrial ("Earth-type") planets
* UsefulNotes/{{Mercury}}: smallest of the planets, closest to the Sun. It is small and very hot (apart from some permanently shadowed craters at the poles which ''may'' contain ice), with [[strike:no]] the merest whisper of an atmosphere. Early scientists believed it to be tide-locked (one side permanently faces the sun), but it turns out it rotates 3 times for every 2 times it circles the sun (which, when combined with an elliptical orbit causes weird effects like "hot" and "cold" poles on the equator, and [[AlienSky the Sun doing a slow loop-the-loop in the sky once each 88-day Mercurian year]]). When ''Mariner 10'' flew by in 1974, it found the planet to be unexpectedly dense; scientists now believe it was originally similar in size and composition to Venus and Earth, but [[EarthShatteringKaboom a massive impact with a leftover planetesimal]] tore away the atmosphere and most of the relatively light mantle, leaving the metal-heavy core behind.
* UsefulNotes/{{Venus}}: sometimes referred to as Earth's sister planet due to their similar sizes. It has an extremely dense atmosphere (surface pressure is 90 bars, compared to 1 on Earth) and can reach a surface temperature of 470 C/870 F (although at the top of Maxwell Montes, almost 7 miles above the average surface level, it's "only" 380 C/716 F and 60 bars). The culprit for all this? The adiabatic lapse rate - 90 atmospheres of anything will be quite hot.[[note]]An Estimate of the Surface Temperature of Venus Independent of Passive Microwave Radiometry by one C. Sagan gives it at ~700K in 1967.[[/note]] Volcanos on Earth have belched out the same amount, [[SealedEvilInACan but it ended up trapped in carbonate rock]]. Venus also started with the same amount of water as the earth had, but it was vaporized (300 atmospheres worth) and created a [[UpToEleven super greenhouse effect]] with temperatures in the ''thousands'' of degrees.[[note]]This plus the slow rotation probably wrecked any chance at plate tectonics; instead of plates constantly sliding against each other, [[LethalLavaLand there seems to be intermittent vulcanism punctuated by the entire surface melting every 500 million years or so]].[[/note]] Eventually the water molecules dissociated into hydrogen and oxygen and escaped into space, leaving Venus high and dry. Interestingly, the zone between 50 and 65 kilometers above the surface has pressures and temperatures right around Earth normal. Add to that the fact that an 80/20 nitrogen/oxygen mix would act like a lifting gas and [[TheEmpireStrikesBack Cloud City]] would be right at home. Due to Venus being mythologically associated with femininity, by convention all geographic features there are named after women or female entities, except for Maxwell Montes and Alpha and Beta Regio.[[note]]These features were first detected by ground-based radar in the mid-1960s; Alpha and Beta Regio were the first two terrain features to be isolated, and Maxwell Montes was named after James Clerk Maxwell, the formulator of the theory and equations of electromagnetism that ultimately led to the invention of radar.[[/note]] There is some argument over whether the proper adjective is 'Venusian', 'Venerean', or 'Cytherean'.
* JustForFun/{{Earth}}: This planet holds [[EarthIsTheCenterOfTheUniverse extreme significance]] for [[PunyEarthlings some underdeveloped carbon-based lifeforms]] despite being just an InsignificantLittleBluePlanet.
** More seriously, Earth is the 6th most massive solar system object, the largest of the Rocky planets, and the most dense object. It is one of two worlds with liquids on the surface, forming rivers, lakes, and such (The other is Saturn's moon Titan, with methane and ethane as the surface liquids), the only one with life (that we know of), and the only one with plate tectonics. The atmosphere is unique in having a large proportion as free oxygen, which in addition to supporting most life, changes the structure in a number of subtle ways compared to other planets. Earth also generates a magnetic field, unlike Venus and Mars, that is much stronger than that of Mercury but weaker than that of the gas giants.
** UsefulNotes/TheMoon: Our nearest neighbor, and the only celestial body beyond Earth that has been explored by humans in person ([[UsefulNotes/ConspiracyTheories allegedly]]).
* UsefulNotes/{{Mars}}: Albedo features identified in the 19th century led to manic speculation about the potential presence of life. Today we know it's not very lively, but that doesn't make it any less interesting. It's still a favorite for space exploration, with a handful of unmanned probes sent there every two years. There are currently five working orbiters around it (''2001 Mars Odyssey'', ''Mars Express'', ''Mars Reconnaissance Orbiter'', ''MAVEN'', and ''Mangalyaan''),[[note]]Respectively sent by NASA, ESA, NASA, NASA, and ISRO (the last being India, for those not up on their space agencies)[[/note]] and two working landers on it (''Opportunity'' and ''Curiosity'').

!! Gas giants
* UsefulNotes/{{Jupiter}}: The largest of them all, and thus fittingly named after the Roman God of Gods. Of course, [[OlderThanTheyThink the Romans named it that long before they had any idea just how big it was]].
** UsefulNotes/TheMoonsOfJupiter: Simon Marius and Galileo Galilei each had claims to the discovery of the first four. Though discovery credit ultimately went to Galileo (and thus, they are known as the Galilean satellites), Marius's names were ultimately used (from innermost out: Io, Europa, Ganymede and Callisto). All the others are named for the daughters and lovers of either Jupiter or his Greek counterpart, Zeus.
* UsefulNotes/{{Saturn}}: Well known for its spectacular ring system. Its average density is less than that of water[[note]]so if you were to put it in a tub of water, it would float[[/note]], and despite its bland butterscotch appearance it has storms that rival any found on Jupiter. Plus it has [[http://en.wikipedia.org/wiki/Saturn#North_pole_hexagonal_cloud_pattern a polar hexagon]]. How cool is that?
** UsefulNotes/TheMoonsOfSaturn: Originally named after Roman deities associated with harvests. When they ran out (Saturn, it turns out, has ''[[{{Understatement}} a lot of moons]]''), they switched to Giants from various mythologies. Norse ice giants are used for newly-discovered moons beyond Phoebe.
** [[http://en.wikipedia.org/wiki/Rings_of_Saturn The Rings Of Saturn]]
* UsefulNotes/{{Uranus}}: It had been detected by astronomers as early as 1690[[note]]John Flamsteed thought it was a star and named it "34 Tauri"; that designation was therefore available for [[JossWhedon a certain talespinner]] to apply to [[{{Series/Firefly}} the star system at the heart of his one of his 'Verses]].[[/note]], but Sir William Herschell actually identified it as a planet in 1789. It's 4 times the diameter of the Earth, which is still less than half the diameter of Jupiter. Seen as minty green in color observed from Earth by early telescopes, close-up observation showed it's more pale blue. It's denser than Jupiter and Saturn with a higher proportion of methane, ammonia and water. Voyager 2 passed by it in 1986 and observed few distinct clouds, [[ScienceMarchesOn but later observations from Earth have revealed more]]. It has a set of coal-black rings (discovered in 1977) and is tilted 98 degrees on its axis - each pole spends 42 years in light and 42 in darkness. Also known for being the planet which the [[Franchise/StarTrek Enterprise]] circles while [[UranusIsShowing wiping out Klingons]].
** UsefulNotes/TheMoonsOfUranus (The Bard [[foldercontrol]]

[[folder: In Space ]]
): Fittingly for an English-discovered planet, Uranus' moons are all named after characters from Creator/WilliamShakespeare. Two of the original five received names from AlexanderPope's ''TheRapeOfTheLock''.
* UsefulNotes/{{Neptune}}: Discovered in 1846 by three different astronomers (John Couch Adams of the UK and Urban Leverrier of France predicted its location independently based on changes in the orbit of Uranus, and Johann Gottfried Galle of Germany found it based on Leverrier's data.). Note, however, [[OlderThanTheyThink that Galileo actually observed Neptune twice in the winter of 1612/13]], but merely noted it appeared to move and never followed up. Watery blue in color; its composition is similar to that of Uranus. Voyager 2 detected some noticeable cloud features when it flew by in 1989, including the "Great Dark Spot" which is an almost perfect analogue to Jupiter's Great Red Spot. It has an unstable ring system that clumps into arcs at some longitudes. From 1979 to 1999 it was further away from the Sun than Pluto, and with a nearly 165-year-long orbital period it has only completed one orbit since its discovery -- and that in 2010.
** UsefulNotes/TheMoonsOfNeptune (Greek deities associated with water)

!!Dwarf Planets

The reason behind the introduction of this category of celestial bodies was a discovery of several Kuiper Belt Objects that rivaled or exceeded [[PlutoIsExpendable Pluto]] in size and thus strained the definition of planet. It was decided that it'd be simpler to demote Pluto than to make all of them planets - [[OlderThanTheyThink a similar course of events took place after the discovery of the first asteroid belt in the 19th century]]. It, rather expectedly, ended in a massive FlameWar among not just enthusiasts of astronomy, but astronomers themselves. For this reason, one of the planets that precipitated the kerfuffle was appropriately named for Eris, the goddess of discord.

To qualify as a dwarf planet, the object must be big enough that its own gravity has pulled it into a more-or-less round shape. (It also can't be orbiting another planet, since then it would be a moon.) To date, only 5 dwarf planets are known:

* [[http://en.wikipedia.org/wiki/Pluto_(dwarf_planet) Pluto]]-[[http://en.wikipedia.org/wiki/Charon_(moon) Charon]][[note]](along with four smaller moons - Nix, Hydra, Kerberos, and Styx)[[/note]]
* [[http://en.wikipedia.org/wiki/Haumea_(dwarf_planet) Haumea]][[note]](it has two moons - Hi'iaka and Namaka)[[/note]]
* [[http://en.wikipedia.org/wiki/Makemake_(dwarf_planet) Makemake]]
* [[http://en.wikipedia.org/wiki/Eris_(dwarf_planet) Eris]][[note]](it is accompanied by a single known moon, Dysnomia)[[/note]]

All these are dark and freezing cold, absolutely no life (except for, probably, [[Creator/HPLovecraft Mi-go]]) could exist or survive here.

* [[http://en.wikipedia.org/wiki/Ceres_(dwarf_planet) Ceres]], the biggest in the asteroid belt, and the only main-belt asteroid big enough to qualify as a dwarf planet. It was also the first "planet" to be demoted, similarly to Pluto but it was first called an asteroid before the class of dwarf planets was invented for Pluto. Apparently some sources still classify it as an asteroid.

!Everything Else
* [[http://en.wikipedia.org/wiki/Asteroid_belt The Asteroid Belt]] -- Also known as the Piazzi Belt (after the discoverer of Ceres) to distinguish it from the Kuiper Belt, it can be found between Mars and Jupiter. It's not an AsteroidThicket -- the belt's combined mass is only 4% of the Moon's, and it's spread out over a volume of space bigger than Earth's entire orbital disc, so unmanned spacecraft generally pass through it without incident.
* [[http://en.wikipedia.org/wiki/Comet Comets]]
** [[http://en.wikipedia.org/wiki/Comet_Halley Halley's Comet]]
* [[http://en.wikipedia.org/wiki/Kuiper_belt The Kuiper Belt]] - named after astronomer Gerard P. Kuiper who theorized its existence in 1951. Also known as the Edgeworth-Kuiper Belt.
* [[http://en.wikipedia.org/wiki/Scattered_disc The Scattered Disc]]
* [[http://en.wikipedia.org/wiki/Oort_cloud The Oort Cloud]] - named after astronomer Jan Oort.

The differences between the last three can be contentious. The Kuiper Belt mostly consists of objects locked into orbital resonance with Neptune. Pluto, along with many other objects known as "plutinos", is locked into a 3:2 resonance. Another class of objects, called "twotinos" are locked into a 2:1 resonance, and other, more arcane resonances exist. The scattered disc consists of objects pushed further out into space by Neptune's outward migration (relatively early in the life of the Solar System); Eris and several other dwarf planets are located here. The Oort cloud consists of objects upon which Neptune's gravity has little significant effect. Since the dividing line for all three is the historical gravitational effect of another astronomical object, one really can't say "at XX AU, the Kuiper belt ends and the scattered disc begins."

The naming of minor Sun-orbiting objects in the Solar System depends on location. Objects in the Main Asteriod Belt are given names from Greek mythology. Objects in the same orbit as Jupiter (the Trojan asteroids) are given names associated with the Trojan War. Objects in similar orbits to Pluto (the "Plutoids") are named after deities of the underworld. Kuiper Belt objects (other objects beyond Neptune's or Pluto's orbits) are named after deities of creation that are ''not'' Greek or Roman.

Turning to nomenclature on a smaller scale, the New Horizons probe will reach Pluto and Charon in July 2015, giving cartographers at least two whole new worlds worth of craters, mountains, and other points of interest to name. Current plans are to name features after various underworld locations and their denizens, spacecraft and space scientists, explorers and their vessels (real and fictional), and artists and authors whose works have depicted exploration. [[http://www.ourpluto.org/ A page has been set up]] to allow people to vote for names to be submitted to the IAU for official use, so cast your vote for a real-life [[Series/{{Firefly}} Vallis Serenity]], [[Literature/WatershipDown Colles Watership]], and [[Series/BabylonFive Regio Z'ha'dum]]! [[note]](sorry, [[Franchise/StarTrek Trekkers]], but [[http://planetarynames.wr.usgs.gov/Feature/15133?__fsk=1962724877 there's already an Enterprise Rupes]] on Mercury[[/note]])

!Interplanetary distances

Most popular depictions of the Solar system, even in science classes, tend to emphasize the relative sizes of the sun and planets and gloss over the scale of the immense distances between them. This can lead to embarrasing instances of ScifiWritersHaveNoSenseOfScale.

Look at the page image for ConvenientlyClosePlanet. That's just the Earth-moon system to scale. The planets are much, much farther apart than this.

If the sun were the size of a bowling ball, the Earth would be roughly the size of a peppercorn, and the distance between them would be nearly ''25 meters''. Jupiter would be the size of a walnut (still in its shell), and would be over ''120'' meters from the sun-bowling-ball. Saturn would be 230 meters from the bowling ball, Uranus would be a peanut 450 meters from the bowling ball, and Neptune would be a whopping 700 meters from the bowling ball (that's nearly ''half a mile'' away from it).
Light (remember, the fastest thing in the Universe and whose velocity cannot be exceeded) at this scale would move [[SarcasmMode at the impressive speed]] of ''166 meters per hour'', and just try to imagine the speed of our current interplanetary probes[[note]]Or don't: the ''Voyager 1'' probe was launched in 1977. It passed Neptune ''12 years later'', traveling at the incredibly fast (by human standards) 11 miles per ''second''. As an aside, Voyager 1 officially passed out of the sun's sphere of influence (the heliosphere) in 2013, ''36 years'' after being launched.[[/note]].
BillNye demonstrates this scale with an exhausting bicycle ride in [[http://www.youtube.com/watch?v=97Ob0xR0Ut8 this video]].

You'll often hear, particularly when concerning the ''Voyager'' probes, that they have reached the "edge" of the Solar System; originally this meant moving beyond Pluto's orbit, a definition that now feels very "last century". Now, it generally means when the "atmosphere" generated by the Sun is pushed back by the atmosphere of interstellar space (a point called the heliopause). And while yes, the space beyond the heliopause is technically the same as the space between stars, it is NOWHERE NEAR the edge of the Sun's gravitational influence, which is a thousand times farther out.