Pluto, formerly the ninth planet, is a complex world of icy mountains and frozen plains. It reigns as the largest known member of the Kuiper Belt.
A complex world of mountains, valleys, and potential glaciers, Pluto was long classified as our ninth
planet. Following the discovery of similar worlds in the Kuiper Belt, it was reclassified as a dwarf
planet.
Pluto possesses five known moons. Charon, the largest, is half Pluto's size. Their unique relationship
often leads to them being described as a "double planet."
Pluto bears the name of the Roman god of the underworld.
New Horizons: Launched in 2006, New Horizons performed a historic flyby of Pluto and its moons in
July 2015. This reconnaissance provided our first detailed look at the dwarf planet's surface and
geology.
Continuing its journey, the spacecraft is now exploring the Kuiper Belt, studying ancient icy bodies
billions of miles beyond Neptune to unlock secrets of the solar system's formation.
With a radius of 715 miles (1,151 kilometers), Pluto is about 1/6th the width of Earth. If Earth were a
nickel, Pluto would be a popcorn kernel.
Orbiting at an average distance of 3.7 billion miles (5.9 billion kilometers) or 39 AU, sunlight takes
5.5 hours to reach it.
At noon on Pluto, the Sun is 1/900th as bright as on Earth—roughly comparable to our twilight.
Pluto's orbit is highly elliptical and tilted. It ranges from 30 AU to 49 AU from the Sun. Occasionally
(as from 1979-1999), it orbits closer than Neptune.
A day on Pluto lasts 153 hours. It rotates on its side (tilted 57 degrees) and spins retrograde (east to
west), like Venus and Uranus.
Pluto resides in the Kuiper Belt, a disc of icy debris beyond Neptune. It formed along with other Kuiper Belt objects about 4.5 billion years ago.
About two-thirds the size of Earth's moon, Pluto likely possesses a rocky core surrounded by a mantle of water ice. Its surface is coated with exotic ices like methane and nitrogen.
Pluto boasts a diverse topography of mountains, valleys, and plains. Temperatures plummet to -400°F
(-240°C).
Mountains of water ice reach heights of 10,000 feet, while vast plains of frozen nitrogen, like Sputnik
Planitia, show signs of convection—slow churning that erases craters over time.
Pluto has a thin, tenuous atmosphere, mainly nitrogen with traces of methane and carbon monoxide. It
expands and collapses with Pluto's distance from the Sun.
During closest approach, surface ices sublimate to form the atmosphere. As Pluto moves away, the
atmosphere freezes and falls back to the surface.
Pluto's frigid surface is hostile to life. However, if a liquid ocean exists deep underground, it could theoretically harbor habitable conditions, though this remains speculative.
Pluto has five moons: Charon, Nix, Hydra, Kerberos, and Styx.
Charon is so large that it and Pluto orbit a common center of gravity outside of Pluto, creating a
binary system. They are tidally locked, always showing the same face to one another.
The small moons spin chaotically, tumbling as they orbit.
There are no known rings around Pluto.
Pluto's small size and slow rotation suggest it likely lacks a significant magnetic field.