Knowra Irregular satellite Irregular satellite An irregular satellite is a natural satellite on a distant orbit that is often eccentric or highly inclined to its planet’s equator. Many are thought to have been captured rather than formed alongside their planets.
Gravitational capture : The acquisition of an orbiting object when gravitational interactions bind it to a larger body. Capture is the leading explanation for how many irregular satellites became bound to their planets.
Jupiter's irregular satellites : Jupiter’s distant natural satellites, which follow eccentric and inclined orbits outside its regular satellite system. Their prograde and retrograde groups include several families attributed to collisional breakup.
Orbital eccentricity : A dimensionless measure of how much an orbit departs from a circle. High eccentricity is common among irregular satellites and distinguishes their paths from nearly circular regular-moon orbits.
Planetary system formation : The processes by which stars, planets, and smaller bodies develop from collapsing clouds of gas and dust. Captured satellites record interactions among planets and leftover small bodies during system formation.
Hill sphere : The region around an astronomical body where its gravity can dominate satellite motion relative to a more distant primary. A planet can retain distant satellites only within the gravitational domain set by its Hill sphere.
Saturn's irregular satellites : Saturn’s distant natural satellites, whose orbits are generally eccentric and strongly inclined. Their clustered orbital groups provide evidence for fragmentation after capture.
Orbital inclination : The angle between an orbit’s plane and a chosen reference plane. Large inclinations, including retrograde motion, are defining features of many irregular satellite orbits.
Solar System small bodies : Asteroids, comets, and other minor objects orbiting the Sun. Irregular satellites may be captured remnants of the small-body populations that surrounded the young planets.
Kozai–Lidov mechanism : A gravitational effect that exchanges orbital inclination and eccentricity in hierarchical systems. It can reshape the eccentric and inclined orbits of distant satellites over long timescales.
Uranus's irregular satellites : Uranus’s distant natural satellites on eccentric, inclined, and often retrograde orbits. Their unusual orbital orientations reflect the complex history of capture around an unusually tilted planet.
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