Editing Planets beyond Neptune (section)

====Sedna's orbit====
{{anchor|Sedna's orbit}}
When [[90377 Sedna|Sedna]] was discovered, its extreme orbit raised questions about its origin. Its perihelion is so distant (approximately {{convert|76|AU|e9km e9mi|abbr=unit}}) that no currently observed mechanism can explain Sedna's eccentric distant orbit. It is too far from the planets to have been affected by the gravity of Neptune or the other giant planets and too bound to the Sun to be affected by outside forces such as the [[galactic tide]]s. Hypotheses to explain its orbit include that it was affected by a passing star, that it was captured from another [[planetary system]], or that it was tugged into its current position by a trans-Neptunian planet.<ref name="Mike">{{Cite journal |last1=Brown |first1=Michael E. |last2=Trujillo |first2=Chadwick |last3=Rabinowitz |first3=David |date=2004 |title=Discovery of a Candidate Inner Oort Cloud Planetoid |journal=The Astrophysical Journal |language=en |volume=617 |issue=1 |pages=645–649 |arxiv=astro-ph/0404456 |bibcode=2004ApJ...617..645B |doi=10.1086/422095 |issn=0004-637X |s2cid=7738201}}</ref> The most obvious solution to determining Sedna's peculiar orbit would be to locate a number of objects in a similar region, whose various orbital configurations would provide an indication as to their history. If Sedna had been pulled into its orbit by a trans-Neptunian planet, any other objects found in its region would have a similar perihelion to Sedna (around {{convert|80|AU|e9km e9mi|abbr=unit}}).<ref name="sisters">{{cite web|title=Searching for Sedna's Sisters: Exploring the inner Oort cloud|last=Schwamb|first=Megan|date=2007-09-18|publisher=Caltech|url=http://www.astro.caltech.edu/~george/option/candex07/schwamb_report.pdf|access-date=2010-08-06|url-status=dead|archive-url=https://web.archive.org/web/20130512221422/http://www.astro.caltech.edu/~george/option/candex07/schwamb_report.pdf|archive-date=2013-05-12}}</ref>