Pluto and Beyond
Frontier Worlds
Frigid Pluto lies in the solar system’s outer reaches. It orbits far from the Sun along with its companion Charon. The surfaces of these two worlds are frozen ice deserts.
| Distance From Sun | 3.7 billion mi (39.5x Earth’s distance from Sun) |
| Structure | rocky core, ices |
| Temperature (Planetary Extremes) | Day -360°F (-218°C); Night -400°F (-240°C) |
| Mass | 450 Plutos = 1 Earth |
| Volume | 170 Plutos could fit inside Earth |
| Day | 6 days, 9 hours, 18 minutes |
| Year | 248 years |
| Axial Tilt | 122° |
The Distant Frontier
The outer solar system is an unexplored wilderness of frozen worlds. Pluto and its largest companion, Charon, orbit there.
Exploring the Kuiper Belt
Pluto and Charon were once thought to bethe most distant outposts of the solar system. We now know they are among the nearest and largest members of a vast population of icy worlds called the Kuiper Belt. It extends out from Neptune’s orbit and contains materials that date back to the formation of the Sun and planets.
Unexplored Pluto
We can observe Pluto from Earth. At the end of the twentieth century, spacecraft had explored many worlds, but not tiny Pluto.
What We Know About Pluto
Pluto’s frigid surface is frosted with methane ice and scarred by dark markings. Charon is covered with water ice. Distance blurs our view of these worlds, but future missions will reveal more details about them.
How Big Are They?
Viewed from Earth, Pluto and Charon are dim specks of light. If they werein orbit around our planet both worlds would be dwarfed by the Moon.
Discoveries at the Frontier
Astronomer Clyde Tombaugh found Pluto on the frontier of the solar system in 1930. Today astronomers regularly discover other worlds in the Kuiper Belt wilderness beyond Neptune and Pluto.
Icy objects like Sedna challenge Pluto’s standingas a planet, as well as our own perceptionof what a planet is. These bodies may be the purest leftovers from the solar system’s birth cloud.