Editing Pluto (section)

== Mass and size ==
[[File:Pluto, Earth & Moon size comparison.jpg|thumb|right|Pluto (bottom left) compared in size to the Earth and the Moon]]Pluto's diameter is {{val|2376.6|3.2|u=km}}<ref name="Nimmo2017" /> and its mass is {{val|1.303|0.003|e=22|u=kg}}, 17.7% that of the [[Moon]] (0.22% that of Earth).<ref name="Davies2001" /> Its [[surface area]] is {{val|1.774443|e=7|u=km2}}, or just slightly bigger than Russia or [[Antarctica]] (particularly including the [[Antarctic sea ice]] during winter). Its [[surface gravity]] is 0.063 ''g'' (compared to 1 ''g'' for Earth and 0.17 ''g'' for the Moon).<ref name="Pluto Fact Sheet"/> This gives Pluto an escape velocity of 4,363.2&nbsp;km per hour / 2,711.167 miles per hour (as compared to Earth's 40,270&nbsp;km per hour / 25,020 miles per hour). Pluto is more than twice the diameter and a dozen times the mass of [[Ceres (dwarf planet)|Ceres]], the largest object in the [[asteroid belt]]. It is less massive than the dwarf planet [[Eris (dwarf planet)|Eris]], a [[trans-Neptunian object]] discovered in 2005, though Pluto has a larger diameter of 2,376.6&nbsp;km<ref name="Nimmo2017" /> compared to Eris's approximate diameter of 2,326&nbsp;km.<ref name="NewHorizons_PlutoSize">{{cite web |url=http://www.nasa.gov/feature/how-big-is-pluto-new-horizons-settles-decades-long-debate |title=How Big Is Pluto? New Horizons Settles Decades-Long Debate |publisher=NASA |date=July 13, 2015 |access-date=July 13, 2015 |archive-date=July 1, 2017 |archive-url=https://web.archive.org/web/20170701005734/https://www.nasa.gov/feature/how-big-is-pluto-new-horizons-settles-decades-long-debate/ |url-status=dead }}</ref>

With less than 0.2 lunar masses, Pluto is much less massive than the [[terrestrial planet]]s, and also less massive than seven [[moons]]: [[Ganymede (moon)|Ganymede]], [[Titan (moon)|Titan]], [[Callisto (moon)|Callisto]], [[Io (moon)|Io]], the [[Moon]], [[Europa (moon)|Europa]], and [[Triton (moon)|Triton]]. The mass is much less than thought before Charon was discovered.<ref>{{cite web |title=Pluto and Charon {{!}} Astronomy |url=https://courses.lumenlearning.com/astronomy/chapter/pluto-and-charon/ |website=courses.lumenlearning.com |access-date=April 6, 2022 |quote=For a long time, it was thought that the mass of Pluto was similar to that of Earth, so that it was classed as a fifth terrestrial planet, somehow misplaced in the far outer reaches of the solar system. There were other anomalies, however, as Pluto's orbit was more eccentric and inclined to the plane of our solar system than that of any other planet. Only after the discovery of its moon Charon in 1978 could the mass of Pluto be measured, and it turned out to be far less than the mass of Earth. |archive-date=March 24, 2022 |archive-url=https://web.archive.org/web/20220324145506/https://courses.lumenlearning.com/astronomy/chapter/pluto-and-charon/ |url-status=live }}</ref>

The discovery of Pluto's satellite [[Charon (moon)|Charon]] in 1978 enabled a determination of the mass of the Pluto–Charon system by application of [[Kepler's laws of planetary motion#Third law|Newton's formulation of Kepler's third law]]. Observations of Pluto in [[occultation]] with Charon allowed scientists to establish Pluto's diameter more accurately, whereas the invention of [[adaptive optics]] allowed them to determine its shape more accurately.<ref name="Close_2000" />

Determinations of Pluto's size have been complicated by its atmosphere<ref name="Young2007" /> and [[hydrocarbon]] haze.<ref name="Plutosize" /> In March 2014, Lellouch, de Bergh et al. published findings regarding methane mixing ratios in Pluto's atmosphere consistent with a Plutonian diameter greater than 2,360&nbsp;km, with a "best guess" of 2,368&nbsp;km.<ref name=Lellouch_2015 /> On July 13, 2015, images from NASA's ''New Horizons'' mission [[Long Range Reconnaissance Imager]] (LORRI), along with data from the other instruments, determined Pluto's diameter to be {{convert|2370|km|abbr=on|sigfig=4}},<ref name = NewHorizons_PlutoSize /><ref name="emily">{{cite web |last1=Lakdawalla |first1=Emily |title=Pluto minus one day: Very first New Horizons Pluto encounter science results |url=http://www.planetary.org/blogs/emily-lakdawalla/2015/07131311-pluto-first-science.html |publisher=[[The Planetary Society]] |date=July 13, 2015 |access-date=July 13, 2015 |archive-date=March 2, 2020 |archive-url=https://web.archive.org/web/20200302200913/https://www.planetary.org/blogs/emily-lakdawalla/2015/07131311-pluto-first-science.html |url-status=live }}</ref> which was later revised to be {{convert|2372|km|abbr=on}} on July 24,<ref name="NHPC_20150724">{{cite AV media |url=https://www.youtube.com/watch?v=dWr29KIs2Ns |title=NASA's New Horizons Team Reveals New Scientific Findings on Pluto |date=July 24, 2015 |publisher=NASA |time=52:30 |access-date=July 30, 2015 |archive-url=https://ghostarchive.org/varchive/youtube/20211028/dWr29KIs2Ns |archive-date=October 28, 2021 |quote=We had an uncertainty that ranged over maybe 70 kilometers, we've collapsed that to plus and minus two, and it's centered around 1186}}{{cbignore}}</ref> and later to {{val|2374|8|u=km}}.<ref name="Stern2015" /> Using [[radio occultation]] data from the ''New Horizons'' Radio Science Experiment (REX), the diameter was found to be {{val|2376.6|3.2|u=km}}.<ref name="Nimmo2017" />

{{image frame
|content={{Graph:Chart
   | width=400
   | height=200
   | type=rect
   | x=Triton,Eris,Pluto,Haumea,Titania,Makemake,Oberon,Rhea,Iapetus,Gonggong,Charon,Quaoar,Ceres,Orcus
   | y1=21.39,16.6,13.03,4.01,3.40,3.1,3.08,2.307,1.806,1.75,1.59,1.4,0.94,0.61
   | showValues=format:.1f, offset:1
   | xAxisAngle=45
}}
|width=440
|caption=The masses of Pluto and Charon compared to other dwarf planets ({{dp|Eris}}, {{dp|Haumea}}, {{dp|Makemake}}, {{dp|Gonggong}}, {{dp|Quaoar}}, {{dp|Orcus}}, {{dp|Ceres}}) and to the icy moons Triton (Neptune I), Titania (Uranus III), Oberon (Uranus IV), Rhea (Saturn V) and Iapetus (Saturn VIII). The unit of mass is {{X10^|21}} kg.
|border=no
}}{{Clear}}