Editing Planets beyond Neptune (section)

====Planet Nine====
{{main article|Planet Nine}}
Planet Nine is a [[List of hypothetical Solar System objects|hypothetical ninth planet]] in the [[outer region of the Solar System]].<ref name=P9H2019/><ref name=TAJ201601>{{cite journal |last1=Batygin |first1=Konstantin |author-link1=Konstantin Batygin |last2=Brown |first2=Michael E. |author-link2=Michael E. Brown |year=2016 |title=Evidence for a Distant Giant Planet in the Solar System |journal=[[The Astronomical Journal]] |volume=151 |issue=2 |page=22 |arxiv=1601.05438 |bibcode=2016AJ....151...22B |doi=10.3847/0004-6256/151/2/22 |s2cid=2701020 |doi-access=free}}</ref> Its gravitational effects could explain the peculiar clustering of [[orbit]]s for a group of [[extreme trans-Neptunian object]]s (ETNOs)—bodies beyond [[Neptune]] that orbit the Sun at distances averaging more than 250&nbsp;times that of the Earth, over 250&nbsp;[[astronomical unit]]s (AU). 
[[File:Planet Nine - black background.png|thumbnail|right|Prediction of hypothetical Planet Nine's orbit based on unique clustering]]
In 2014, astronomers announced the discovery of {{mpl|2012 VP|113}}, a large object with a Sedna-like 4,200-year orbit and a perihelion of roughly 80 AU,<ref name="nature letter"/> which led them to suggest that it offered evidence of a potential trans-Neptunian planet.<ref>{{cite web |url=http://phys.org/news/2014-03-edge-solar.html |title=A new object at the edge of our Solar System discovered |work=Physorg.com |date=26 March 2014}}</ref> [[Chad Trujillo|Trujillo]] and [[Scott S. Sheppard|Sheppard]] argued that the orbital clustering of [[argument of perihelion|arguments of perihelia]] for {{mp|2012 VP|113}} and other extremely distant TNOs suggests the existence of a "[[super-Earth]]" of between 2 and 15 Earth masses beyond 200 AU and possibly on an inclined orbit at 1,500 AU.<ref name="nature letter"/>

In 2014 astronomers at the [[Universidad Complutense]] in [[Madrid]] suggested that the available data actually indicates more than one trans-Neptunian planet;<ref name="Marcos2014">{{cite journal| title=Extreme trans-Neptunian objects and the Kozai mechanism: signalling the presence of trans-Plutonian planets| first1=C.| last1=de la Fuente Marcos| first2=R.| last2=de la Fuente Marcos| date=1 September 2014|journal=Monthly Notices of the Royal Astronomical Society: Letters| volume=443| issue=1| pages=L59–L63| arxiv=1406.0715| bibcode=2014MNRAS.443L..59D |doi=10.1093/mnrasl/slu084| doi-access=free| s2cid=118622180}}</ref> subsequent work further suggests that the evidence is robust enough but rather than connected with the longitudes of the ascending nodes and the arguments of perihelia, semi-major axes and nodal distances could be the signposts.<ref name=commensurabilities>{{cite journal |last1=de la Fuente Marcos |first1=Carlos |last2=de la Fuente Marcos |first2=Raúl |date=2016 |title=Commensurabilities between ETNOs: a Monte Carlo survey |journal=[[Monthly Notices of the Royal Astronomical Society Letters]] |volume=460 |issue=1 |pages=L64–L68 |arxiv=1604.05881 |bibcode=2016MNRAS.460L..64D |doi=10.1093/mnrasl/slw077|doi-access=free |s2cid=119110892 }}</ref><ref name=nodes>{{cite journal |last1=de la Fuente Marcos |first1=Carlos |last2=de la Fuente Marcos |first2=Raúl |date=11 October 2017 |title=Evidence for a possible bimodal distribution of the nodal distances of the extreme trans-Neptunian objects: avoiding a trans-Plutonian planet or just plain bias? |journal=[[Monthly Notices of the Royal Astronomical Society Letters]] |volume=471 |issue=1 |pages=L61–L65 |arxiv=1706.06981 |bibcode=2017MNRAS.471L..61D |doi=10.1093/mnrasl/slx106|doi-access=free |s2cid=55469849 }}</ref> Additional work based on improved orbits of 39 objects still indicates that more than one perturber could be present and that one of them could orbit the Sun at 300-400 AU.<ref name="randomsearch">{{cite journal |last1=de la Fuente Marcos |first1=C. |last2=de la Fuente Marcos | first2= R.|title=Memories of past close encounters in extreme trans-Neptunian space: Finding unseen planets using pure random searches  |journal=Astronomy and Astrophysics Letters |volume=646 |page=L14 (9 pp) |date=18 February 2021 |doi=10.1051/0004-6361/202140311 |arxiv=2102.02220 |bibcode=2021A&A...646L..14D |s2cid= 231802033| url=https://www.aanda.org/articles/aa/full_html/2021/02/aa40311-21/aa40311-21.html}}</ref>

On January 20, 2016, Brown and [[Konstantin Batygin]] published an article corroborating Trujillo and Sheppard's initial findings; proposing a super-Earth (dubbed [[Planet Nine]]) based on a statistical clustering of the arguments of perihelia (noted before) near zero and also [[ascending node]]s near 113° of six distant [[trans-Neptunian object]]s. They estimated it to be ten times the mass of [[Earth]] (about 60% the mass of Neptune) with a [[semimajor axis]] of approximately 400–1500 [[astronomical unit|AU]].<ref name="AJ121-2-22">{{cite journal|title=Evidence for a distant giant planet in the Solar system|first1=Konstantin|last1=Batygin|first2=Michael E.|last2=Brown|date=20 January 2016|journal=[[The Astronomical Journal]]|volume=151|number=2|doi=10.3847/0004-6256/151/2/22|pages=22|arxiv = 1601.05438 |bibcode = 2016AJ....151...22B |s2cid=2701020 |doi-access=free }}</ref><ref name="NYT-20160120">{{cite news |last=Chang |first=Kenneth |title=Ninth Planet May Exist Beyond Pluto, Scientists Report |url=https://www.nytimes.com/2016/01/21/science/space/ninth-planet-solar-system-beyond-pluto.html |date=20 January 2016 |work=[[The New York Times]] |access-date=22 January 2016 }}</ref><ref>{{Cite news|title = New evidence suggests a ninth planet lurking at the edge of the solar system|url = https://www.washingtonpost.com/news/speaking-of-science/wp/2016/01/20/new-evidence-suggests-a-ninth-planet-lurking-at-the-edge-of-the-solar-system/|newspaper = The Washington Post|date = 2016-01-20|access-date = 2016-01-20|language = en-US|first1 = Joel|last1 = Achenbach|first2 = Rachel|last2 = Feltman}}</ref>