According to this definition, Pluto, some asteroids, and the Earth's moon (AKA Luna)
are planets, as are many other objects. For objects in the Kuiper belt and beyond, this chart features the
most likely planet candidates and is subject to change. Objects that were formerly round and have since been
deformed by impacts are included here as remnant planets and are marked with an asterisk. Scroll down for a
glossary and image credits.
Type: A category of planets based on their approximate composition (what the
planet is made of).
Terrestrial: Made mostly of rock.
Asteroidal: Made mostly of rock and hydrated minerals (rocks with
water trapped inside).
Glacial: Made mostly of rock and ice (includes frozen water, ammonia,
Gas Giant: Made mostly of hydrogen and helium.
Ice Giant: Made mostly of other gases and ice.
Family: The population of objects the planet is part of.
Inner Planets: The planets closest to the Sun. Not a formal
Asteroids: Objects in the asteroid belt, a loose region of rocky
bodies between the orbits of Mars and Jupiter.
Outer Planets: The giant planets and their satellites (moons). Not a
Kuiper Belt Objects: Objects in the Kuiper belt, a loose region of icy
bodies beyond Neptune (roughly 30 to 50 AU from the Sun).
Scattered Disk Objects: Distant objects scattered from the Kuiper belt
by the giant planets' gravity, now forming a loose belt.
Detached Objects: Very distant objects, only moderately affected by
the giant planets' gravity.
Mean Diameter: The average width of the planet. No planet is a perfect
sphere, so this number averages the equatorial diameter, polar diameter, etc.
Mass: How much material the planet is made up of.
Mean Density: How much mass the planet has per unit volume.
Surface Gravity: Average strength of gravity at the planet's surface.
Orbital Period: How long it takes the planet to complete an orbit (year
Rotational Period: How long it takes the planet to rotate about its axis (day
Axial Tilt: How angled the planet's rotational axis is from its orbit.
Periapsis/Apoapsis: The closest/farthest an object gets to the body it
orbits. Each object with planets orbiting it has special periapsis and apoapsis names:
Perihelion/Aphelion: How close/far an object gets to the Sun
Perigee/Apogee: How close/far an object gets to Earth.
Perijove/Apojove: How close/far an object gets to Jupiter.
Perichron/Apochron: How close/far an object gets to Saturn.
Periuranion/Apouranion: How close/far an object gets to Uranus.
Periposeidion/Apoposeidion: How close/far an object gets to Neptune.
Perihadion/Apohadion: How close/far an object gets to Pluto.
Eccentricity: A number between zero and one that shows how elliptical
(stretched out) a planet's orbit is. The higher the eccentricity, the farther apart a planet's periapsis and
apoapsis are. Zero eccentricity is a perfect circle, 0.01 is slightly elliptical, 0.5 is very elliptical,