Editing Apsis (section)

===Short arcs===
[[Trans-Neptunian object]]s discovered when 80+ AU from the Sun need dozens of observations over multiple years to well constrain their orbits because they move very slowly against the background stars. Due to statistics of small numbers, trans-Neptunian objects such as {{mpl|2015 TH|367}} when it had only 8 observations over an [[observation arc]] of 1 year that have not or will not come to perihelion for roughly 100 years can have a [[68–95–99.7 rule|1-sigma]] uncertainty of {{Convert|28220|day|year|order=flip|abbr=off}} in the perihelion date.<ref>{{Cite web |url=https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2015TH367 |title=JPL SBDB: 2015 TH367 |access-date=September 23, 2021 |archive-date=March 14, 2018 |archive-url=https://web.archive.org/web/20180314133928/https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2015TH367 |url-status=bot: unknown }}</ref>