Solar System

Kepler's equation

Kepler's equation is the relation M = E - e sin E connecting position on an elliptical orbit to elapsed time, solved only by numerical iteration.

Kepler's laws of planetary motion

Kepler's laws of planetary motion, published by Johannes Kepler between 1609 and 1619, state that planets orbit the Sun in ellipses, sweep equal areas in equal times, and obey a period-distance relation.

Kerberos

Kerberos (S/2011 (134340) 1, P4) is a small moon of Pluto discovered by Hubble in 2011, orbiting between Nix and Hydra with a 32.17-day period, a double-lobed ~19 km body of bright water ice.

Ketu (केतु) (mythology)

Ketu (केतु) is one of the nine planetary deities of Hindu astrology, personifying the descending lunar node and paired with Rahu; the two are linked with eclipses.

Khalanasy Vallis

Khalanasy Vallis, an IAU-approved 1997 valley (vallis) on Venus, 320 km across, centered at 51S 168.5E, named for an Azeri river mermaid; one of 72 named Venusian valles.

Kirkwood gap

A Kirkwood gap, such as the Hecuba gap, is a depleted band of main-belt asteroids at a mean-motion resonance with Jupiter, named for astronomer Daniel Kirkwood, who announced the gaps in 1866.

Klaatu (The Day the Earth Stood Still)

Klaatu is the humanoid alien emissary of the 1951 science fiction film The Day the Earth Stood Still, portrayed by Michael Rennie and known for the command "Klaatu barada nikto".

Kore

Kore, also designated Jupiter XLIX and provisionally S/2003 J 14, is a small retrograde moon of Jupiter in the Pasiphae group, discovered in 2003 at Mauna Kea and named by the IAU in 2007.

Kozai mechanism

The Kozai mechanism, also called the Kozai–Lidov or Kozai–Lidov–von Zeipel mechanism, is a secular three-body effect in which an inclined perturber drives anti-correlated oscillations of an orbit's inclination and eccentricity.

Kūmsong Vallis

Kūmsong Vallis (Kumsong Vallis), a 700 km valley system on Venus centered at -59.00°, 152.50°E, IAU-approved in 1997, named with the Korean word for the planet Venus.

Lagrange points

Lagrange points are five positions near two orbiting bodies, such as the Sun and Earth, where a small object can hold a fixed position; spacecraft use them as parking spots.

Laplace plane

The Laplace plane is the reference plane about which a satellite's orbit precesses on average, an idea Pierre-Simon Laplace recognized in 1805 in his study of Jupiter's satellites.

Laplace resonance

The Laplace resonance is a three-body orbital resonance in which Jupiter's moons Io, Europa, and Ganymede orbit in a 1:2:4 period ratio, driving tidal heating.

Late Heavy Bombardment

The Late Heavy Bombardment, also called the lunar cataclysm, is a hypothesized period of intense asteroid impacts in the inner Solar System around 3.9 billion years ago.

Leonids

The Leonids are an annual meteor shower peaking in mid-November, produced by debris from comet 55P/Tempel-Tuttle and radiating from Leo, capable of meteor storms every 33 years.

Life on Mars

Life on Mars is the scientific question of whether life exists or ever existed on Mars; none has been confirmed, though organic molecules and potential biosignatures have been found.

Life on Titan

Life on Titan, also called Titanian life, is a hypothesized possibility studied in astrobiology: Saturn's moon Titan has liquid methane lakes and a possible subsurface ocean.

Life on Venus

Life on Venus, also known as habitability of Venus, is the scientific question of whether life exists or ever existed there, focusing on microbial life in the clouds.

Lion and Sun (شیر و خورشید)

The Lion and Sun (شیر و خورشید, Shir o khorshid) is a historical national emblem of Iran, on the flag from 1906 until the 1979 Islamic Revolution.

List of artificial objects leaving the Solar System

The list of artificial objects leaving the Solar System covers five NASA spacecraft: Pioneer 10, Pioneer 11, Voyager 1, Voyager 2, and New Horizons, launched between 1972 and 2006.

List of asteroid close approaches to Earth

The list of asteroid close approaches to Earth catalogs near-Earth objects passing within 0.05 au of Earth; the closest on record, in 2025, passed about 230 km up.

List of gravitationally rounded objects of the Solar System

The list of gravitationally rounded objects of the Solar System covers the bodies massive enough for gravity to make them round: eight planets, five dwarf planets, and about nineteen large moons.

List of minor planets

The list of minor planets, also called the Minor Planet Catalogue, is the official International Astronomical Union catalog of numbered asteroids and other small bodies orbiting the Sun.

List of minor planets: 1–1000

The list of minor planets 1–1000 covers the first thousand asteroids numbered by the International Astronomical Union, from Ceres, discovered in 1801, to minor planet (1000), announced in 1923.

List of minor planets: 10001–11000

The list of minor planets 10001–11000 covers 1,000 consecutively numbered asteroids with permanent numbers from the Minor Planet Center, each paired with its provisional discovery designation.

List of minor planets: 15001–16000

The list of minor planets 15001–16000 catalogs 1,000 consecutively numbered minor planets, discovered between 1940 and 2000, with entries for designations, discovery circumstances, and Sun distance.

List of minor planets: 16001–17000

The list of minor planets 16001–17000 is a partial catalog of numbered minor planets, objects whose orbits were confirmed and numbered sequentially by the Minor Planet Center.

List of minor planets: 20001–21000

The list of minor planets 20001–21000 is a segment of the Minor Planet Center's catalog of 1,000 numbered small Solar System bodies, mostly discovered during 1991–1994 surveys.

List of minor planets: 21001–22000

The list of minor planets 21001–22000 covers one thousand consecutively numbered minor planets in the Minor Planet Center's catalog, including both named and unnamed bodies.