Query: Pluto's climate change over the last 14 years is likely a seasonal event.

Relevant passages:
Planet <=SEP=> A planet is an astronomical body orbiting a star or stellar remnant that  is massive enough to be rounded by its own gravity ,  is not massive enough to cause thermonuclear fusion , and  has cleared its neighbouring region of planetesimals.This definition is drawn from two separate IAU declarations ; a formal definition agreed by the IAU in 2006 , and an informal working definition established by the IAU in 2001/2003 for objects outside of the Solar System . The official 2006 definition applies only to the Solar System , whereas the 2003 definition applies to planets around other stars . The extrasolar planet issue was deemed too complex to resolve at the 2006 IAU conference .  The term planet is ancient , with ties to history , astrology , science , mythology , and religion . Several planets in the Solar System can be seen with the naked eye . These were regarded by many early cultures as divine , or as emissaries of deities . As scientific knowledge advanced , human perception of the planets changed , incorporating a number of disparate objects . In 2006 , the International Astronomical Union ( IAU ) officially adopted a resolution defining planets within the Solar System . This definition is controversial because it excludes many objects of planetary mass based on where or what they orbit . Although eight of the planetary bodies discovered before 1950 remain `` planets '' under the modern definition , some celestial bodies , such as Ceres , Pallas , Juno and Vesta ( each an object in the solar asteroid belt ) , and Pluto ( the first trans-Neptunian object discovered ) , that were once considered planets by the scientific community , are no longer viewed as such .   The planets were thought by Ptolemy to orbit Earth in deferent and epicycle motions . Although the idea that the planets orbited the Sun had been suggested many times , it was not until the 17th century that this view was supported by evidence from the first telescopic astronomical observations , performed by Galileo Galilei . At about the same time , by careful analysis of pre-telescopic observation data collected by Tycho Brahe , Johannes Kepler found the planets ' orbits were not circular but elliptical . As observational tools improved , astronomers saw that , like Earth , the planets rotated around tilted axes , and some shared such features as ice caps and seasons . Since the dawn of the Space Age , close observation by space probes has found that Earth and the other planets share characteristics such as volcanism , hurricanes , tectonics , and even hydrology .   Planets are generally divided into two main types : large low-density giant planets , and smaller rocky terrestrials . Under IAU definitions , there are eight planets in the Solar System . In order of increasing distance from the Sun , they are the four terrestrials , Mercury , Venus , Earth , and Mars , then the four giant planets , Jupiter , Saturn , Uranus , and Neptune . Six of the planets are orbited by one or more natural satellites .   Several thousands of planets around other stars ( `` extrasolar planets '' or `` exoplanets '' ) have been discovered in the Milky Way . As of , known extrasolar planets in planetary systems ( including multiple planetary systems ) , ranging in size from just above the size of the Moon to gas giants about twice as large as Jupiter have been discovered , out of which more than 100 planets are the same size as Earth , nine of which are at the same relative distance from their star as Earth from the Sun , i.e. in the habitable zone . On December 20 , 2011 , the Kepler Space Telescope team reported the discovery of the first Earth-sized extrasolar planets , Kepler-20e and Kepler-20f , orbiting a Sun-like star , Kepler-20 . A 2012 study , analyzing gravitational microlensing data , estimates an average of at least 1.6 bound planets for every star in the Milky Way .  Around one in five Sun-like stars is thought to have an Earth-sized planet in its habitable zone .

Neptune <=SEP=> Neptune is the eighth and farthest known planet from the Sun in the Solar System . In the Solar System , it is the fourth-largest planet by diameter , the third-most-massive planet , and the densest giant planet . Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus , which is 15 times the mass of Earth and slightly larger than Neptune.Neptune is denser and physically smaller than Uranus because Neptune 's greater mass gravitationally compresses the atmosphere more . Neptune orbits the Sun once every 164.8 years at an average distance of 30.1 AU . It is named after the Roman god of the sea and has the astronomical symbol ♆ , a stylised version of the god Neptune 's trident .   Neptune is not visible to the unaided eye and is the only planet in the Solar System found by mathematical prediction rather than by empirical observation . Unexpected changes in the orbit of Uranus led Alexis Bouvard to deduce that its orbit was subject to gravitational perturbation by an unknown planet . Neptune was subsequently observed with a telescope on 23 September 1846 by Johann Galle within a degree of the position predicted by Urbain Le Verrier . Its largest moon , Triton , was discovered shortly thereafter , though none of the planet 's remaining known 14 moons were located telescopically until the 20th century . The planet 's distance from Earth gives it a very small apparent size , making it challenging to study with Earth-based telescopes . Neptune was visited by Voyager 2 , when it flew by the planet on 25 August 1989 . The advent of the Hubble Space Telescope and large ground-based telescopes with adaptive optics has recently allowed for additional detailed observations from afar .   Neptune 's composition can be compared and contrasted with the Solar System 's other giant planets . Like Jupiter and Saturn , Neptune 's atmosphere is composed primarily of hydrogen and helium , along with traces of hydrocarbons and possibly nitrogen , but it contains a higher proportion of `` ices '' such as water , ammonia , and methane . However , its interior , like that of Uranus , is primarily composed of ices and rock , which is why Uranus and Neptune are normally considered `` ice giants '' to emphasise this distinction . Traces of methane in the outermost regions in part account for the planet 's blue appearance .   In contrast to the hazy , relatively featureless atmosphere of Uranus , Neptune 's atmosphere has active and visible weather patterns . For example , at the time of the Voyager 2 flyby in 1989 , the planet 's southern hemisphere had a Great Dark Spot comparable to the Great Red Spot on Jupiter . These weather patterns are driven by the strongest sustained winds of any planet in the Solar System , with recorded wind speeds as high as 2100 km/h . Because of its great distance from the Sun , Neptune 's outer atmosphere is one of the coldest places in the Solar System , with temperatures at its cloud tops approaching 55 K. Temperatures at the planet 's centre are approximately 5400 K. Neptune has a faint and fragmented ring system ( labelled `` arcs '' ) , which was first detected during the 1960s and confirmed by Voyager 2 .

Uranus <=SEP=> Uranus is the seventh planet from the Sun . It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System . Uranus is similar in composition to Neptune , and both have different bulk chemical composition from that of the larger gas giants Jupiter and Saturn . For this reason , scientists often classify Uranus and Neptune as `` ice giants '' to distinguish them from the gas giants . Uranus 's atmosphere is similar to Jupiter 's and Saturn 's in its primary composition of hydrogen and helium , but it contains more `` ices '' such as water , ammonia , and methane , along with traces of other hydrocarbons . It is the coldest planetary atmosphere in the Solar System , with a minimum temperature of 49 K , and has a complex , layered cloud structure with water thought to make up the lowest clouds and methane the uppermost layer of clouds . The interior of Uranus is mainly composed of ices and rock .   Uranus is the only planet whose name is derived from a figure from Greek mythology , from the Latinised version of the Greek god of the sky Ouranos . Like the other giant planets , Uranus has a ring system , a magnetosphere , and numerous moons . The Uranian system has a unique configuration among those of the planets because its axis of rotation is tilted sideways , nearly into the plane of its solar orbit . Its north and south poles , therefore , lie where most other planets have their equators . In 1986 , images from Voyager 2 showed Uranus as an almost featureless planet in visible light , without the cloud bands or storms associated with the other giant planets . Observations from Earth have shown seasonal change and increased weather activity as Uranus approached its equinox in 2007 . Wind speeds can reach 250 m/s .