Retrograde and prograde motion

Retrograde motion in astronomy is, in general, <a href="/facts/Orbit/nD2TPySG">orbital</a> or <a href="/facts/Rotation/yChkz49x">rotational</a> motion of an object in the direction opposite the rotation of its <a href="/facts/Primary_(astronomy)/PzvXx42a">primary</a>, that is, the central object (right figure). It may also describe other motions such as <a href="/facts/Axial_precession/NQ79x3m3">precession</a> or <a href="/facts/Astronomical_nutation/Rv0HN28Y">nutation</a> of an object's <a href="/facts/Rotation_around_a_fixed_axis/PGcg3IY5">rotational axis</a>. Prograde or direct motion is more normal motion in the same direction as the primary rotates. However, "retrograde" and "prograde" can also refer to an object other than the primary if so described. The direction of rotation is determined by an <a href="/facts/Inertial_frame_of_reference/1U6TrdG3">inertial frame of reference</a>, such as distant <a href="/facts/Fixed_stars/grlDbIPX">fixed stars</a>.
In the <a href="/facts/Solar_System/QIcLSazQ">Solar System</a>, the orbits around the <a href="/facts/Sun/CadPCVHh">Sun</a> of all <a href="/facts/Planet/rbPjE6Bx">planets</a> and <a href="/facts/Dwarf_planets/IkQoCdwD">dwarf planets</a> and most <a href="/facts/Small_Solar_System_body/Vrnr9n3M">small Solar System bodies</a>, except many <a href="/facts/Comet/w34utQCd">comets</a> and few <a href="/facts/Distant_minor_planet/WppkoW1G">distant objects</a>, are prograde. They orbit around the Sun in the same direction as the sun rotates about its axis, which is <a href="/facts/Counterclockwise/3Npe4Swe">counterclockwise</a> when observed from above the Sun's north pole. Except for <a href="/facts/Venus/pADnueP6">Venus</a> and <a href="/facts/Uranus/x7YwT1ar">Uranus</a>, planetary rotations around their axis are also prograde. Most <a href="/facts/Natural_satellite/AE4KQKbq">natural satellites</a> have prograde orbits around their planets. Prograde satellites of Uranus orbit in the direction Uranus rotates, which is retrograde to the Sun. Nearly all <a href="/facts/Regular_satellite/61pC7mzC">regular satellites</a> are <a href="/facts/Tidally_locked/E3W4dEBj">tidally locked</a> and thus have prograde rotation. Retrograde satellites are generally <a href="/facts/Irregular_satellite/TCaaa16K">small and distant</a> from their planets, except <a href="/facts/Neptune/1eucwHIC">Neptune</a>'s satellite <a href="/facts/Triton_(moon)/mxxRUygc">Triton</a>, which is large and close. All retrograde satellites are thought to have formed separately before being <a href="/facts/Asteroid_capture/bf2tB9zC">captured</a> by their planets.
Most low-inclination <a href="/facts/Artificial_satellite/PTX8c68t">artificial satellites</a> of Earth have been placed in a prograde orbit, because in this situation less propellant is required to reach the orbit.

Retrograde and prograde motion open-in-new

Retrograde and prograde motion