Editing Orbital speed (section)

== Planets ==
The closer an object is to the Sun the faster it needs to move to maintain the orbit. Objects move fastest at perihelion (closest approach to the Sun) and slowest at aphelion (furthest distance from the Sun). Since planets in the Solar System are in nearly circular orbits their individual orbital velocities do not vary much. Being closest to the Sun and having the most eccentric orbit, Mercury's orbital speed varies from about 59 km/s at perihelion to 39 km/s at aphelion.<ref name="Mercury">{{cite web
  |title      = Horizons Batch for Mercury aphelion (2021-Jun-10) to perihelion (2021-Jul-24)
  |type       = VmagSn is velocity with respect to Sun.
  |url        = https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%271%27&START_TIME=%272021-Jun-10%27&STOP_TIME=%272021-Jul-24%27&STEP_SIZE=%271%20day%27&QUANTITIES=%2720,22%27&CENTER=%27@Sun%27
  |work       = [[JPL Horizons On-Line Ephemeris System|JPL Horizons]]
  |publisher  = Jet Propulsion Laboratory
  |access-date= 26 August 2021}}</ref>

{|class="wikitable" style="text-align:center; font-size:0.9em;"
|+Orbital velocities of the Planets<ref>{{Cite web|url=https://public.nrao.edu/ask/which-planet-orbits-our-sun-the-fastest/|title=Which Planet Orbits our Sun the Fastest?}}</ref>
! Planet
! Orbital<br />velocity
|-
| [[Mercury (planet)|Mercury]] || {{convert |47.9|km/s|mi/s|abbr=on}}
|-
| [[Venus]] || {{convert |35.0|km/s|mi/s|abbr=on}}
|-
| [[Earth]] || {{convert |29.8|km/s|mi/s|abbr=on}}
|-
| [[Mars]] || {{convert |24.1|km/s|mi/s|abbr=on}}
|-
| [[Jupiter]] || {{convert |13.1|km/s|mi/s|abbr=on}}
|-
| [[Saturn]] || {{convert |9.7|km/s|mi/s|abbr=on}}
|-
| [[Uranus]] || {{convert |6.8|km/s|mi/s|abbr=on}}
|-
| [[Neptune]] || {{convert |5.4|km/s|mi/s|abbr=on}}
|}

[[Halley's Comet]] on an [[Orbital eccentricity|eccentric orbit]] that reaches beyond [[Neptune]] will be moving 54.6&nbsp;km/s when {{convert|0.586|AU|e3km|abbr=unit|lk=on}} from the Sun, 41.5&nbsp;km/s when 1 AU from the Sun (passing Earth's orbit), and roughly 1&nbsp;km/s at aphelion {{convert|35|AU|e9km|abbr=unit}} from the Sun.<ref>{{nowrap|1=''v'' = 42.1219 {{radic|1/''r'' − 0.5/''a''}}}}, where ''r'' is the distance from the Sun, and ''a'' is the major semi-axis.</ref> Objects passing Earth's orbit going faster than 42.1 km/s have achieved [[Escape velocity#List of escape velocities|escape velocity]] and will be ejected from the Solar System if not slowed down by a [[Perturbation (astronomy)|gravitational interaction]] with a planet.

{|class="wikitable sortable" style="text-align:center; font-size:0.9em;"
|+Velocities of better-known numbered objects that have perihelion close to the Sun
! Object
! Velocity at perihelion
! Velocity at 1 AU<br/>(passing Earth's orbit)
|-
| [[322P/SOHO]] || 181 km/s @ 0.0537 AU || 37.7 km/s
|-
| [[96P/Machholz]] || 118 km/s @ 0.124 AU || 38.5 km/s
|-
| [[3200 Phaethon]] || 109 km/s @ 0.140 AU || 32.7 km/s
|-
| [[1566 Icarus]] || 93.1 km/s @ 0.187 AU || 30.9 km/s
|-
| [[66391 Moshup]] || 86.5 km/s @ 0.200 AU || 19.8 km/s
|-
| [[1P/Halley]] || 54.6 km/s @ 0.586 AU ||  41.5 km/s
|}