Notes

Discovered in 1930, Pluto was long considered our solar system's ninth planet. But after the discovery of similar intriguing worlds deeper in the distant Kuiper Belt, icy Pluto was reclassified as a dwarf planet. Findings by NASA's New Horizons in 2015 revealed for the first time how that Pluto is a complex and mysterious world. Information about Pluto and its largest moon, Charon, provide insight into the collision believed to have formed the dwarf planet and moons we see today.

Dwarf planets may provide the best evidence about the origins of our solar system.

If the sun were as tall as a typical front door, Earth would be the size of a nickel and dwarf planet Pluto would be about the size of the head of a pin.

Pluto orbits our sun, a star, at an average distance of 3.7 billion miles (5.9 billion kilometers) or 39.5 AU.

One day on Pluto takes about 153 hours. That's the time it takes for Pluto to rotate or spin once. Pluto makes a complete orbit around the sun (a year in Plutonian time) in about 248 Earth years.

It is thought that Pluto has a rocky core surrounded by a mantle of water ice with other ices coating its surface.

Pluto has five known moons. Pluto is sometimes called a double-planet system due to the fact that its moon Charon is quite large and orbits close to its parent planet.

NASA's New Horizons spacecraft is the first mission sent to encounter the Pluto-system and other members of the Kuiper Belt.

There are no known rings around Pluto.

Pluto has a thin, tenuous atmosphere that expands when it comes closer to the sun and collapses as it moves farther away -- similar to a comet.

Scientists do not think Pluto can support life as we know it. Although, some scientists believe it is possible Pluto could possess a hidden ocean under its surface.

Pluto was considered a planet from 1930, when it was first discovered, until 2006. The discovery of similar-sized worlds deeper in the distant Kuiper Belt sparked a debate which resulted in a new official definition of a planet. The new definition did not include Pluto.