1. The Dwarf Planet You've Never Heard Of

Pluto is the tenth-most-massive celestial body that has been observed directly orbiting the Sun. This dwarf planet, which was once considered to be the ninth planet in our Solar System, has a mass that is approximately 0.2% of the mass of the Earth. It is the second-most-distant known object in the Solar System, after Eris, and is located an average of 39.5 astronomical units away from the Sun.

Also → Neptune is the most massive planet in our Solar System

2. The Second-Most-Massive Known Dwarf Planet

Pluto is the second-most-massive known dwarf planet in the Solar System, with a mass estimated to be around 0.2% that of Earth's. It is slightly less massive than Eris, the most massive known dwarf planet, which has a mass estimated to be around 27% that of Earth's. Both dwarf planets are located in the Kuiper Belt, a region of icy bodies beyond the orbit of Neptune.

Also → Jupiter: The Largest Planet in the Solar System

3. The Girl Who Named Pluto

On March 24, 1930, an eleven-year-old schoolgirl named Venetia Burney from Oxford, England made history when she proposed the name "Pluto" for the newly discovered planet. Venetia was a passionate student of both classical mythology and astronomy, and felt that the name of the god of the underworld was an appropriate fit for the dark and cold world. Her suggestion was accepted and Pluto was officially named, making her the first person to name a planet in our solar system.

Also → Saturn: The Second Largest Planet in the Solar System

4. The Dog Named After a Planet

In 1930, Walt Disney introduced a canine companion to the world, aptly named Pluto. Although the reason for the name remains a mystery, it is believed that Disney was inspired by the planet of the same name. Animator Ben Sharpsteen, who worked closely with Disney, was unable to confirm the reason for the name choice. Regardless, the name has since become synonymous with Disney's beloved cartoon character.

Also → Uranus: The Fourth-Largest Planet in the Solar System

5. A Kuiper-belt Object Made of Rock and Ice

Pluto, a Kuiper-belt object, is composed of rock and ice and is much smaller than the Earth's Moon. It has a mass of only one-sixth that of the Moon and a volume of one-third. This makes Pluto a fascinating celestial body, as it is much smaller than the Moon yet still has a significant presence in our Solar System.

Also → Venus: The Second Planet from the Sun

6. Pluto Named After New Planet

In 1941, Glenn T. Seaborg made a groundbreaking discovery when he created the element plutonium and named it after the newly discovered planet Pluto. This was in keeping with the tradition of naming elements after newly discovered planets, such as uranium, which was named after Uranus, and neptunium, which was named after Neptune. This discovery was a major milestone in the history of science and marked the first time an element had been named after a planet beyond Neptune.

Also → Mercury: The Innermost Planet

7. Dwarf Planet or Major Planet?

In 1930, Pluto was discovered and classified as the ninth planet from the Sun. For the next 75 years, its status as a major planet was questioned as more research was conducted on Pluto and the outer Solar System. This led to a reclassification of Pluto as a dwarf planet in 2006, making it the first trans-Neptunian object to be officially recognized as such. Despite this, Pluto still remains an important part of our Solar System and continues to be studied by astronomers.

Also → Mars: A Fascinating Planet

8. Scientists Want to Add Another Dwarf Planet to the List of Planets

Despite the fact that Pluto was reclassified as a dwarf planet in 2006, many scientists still believe that it should have remained classified as a planet, and that other dwarf planets should be added to the list of planets in our Solar System. This would mean that the number of planets in our Solar System would increase from 8 to 12, with Pluto, Ceres, Eris, Haumea, Makemake, and Sedna joining the traditional 8 planets. This would be a major shift in our understanding of the Solar System, and would require a re-evaluation of the way we teach astronomy in schools.

9. Five Moons with Unique Properties

Pluto, the ninth planet from the Sun, is home to five known moons: Charon, the largest of the five, has a diameter just over half that of Pluto; Nix and Hydra, two small moons discovered in 2005; Kerberos, a small moon discovered in 2011; and Styx, a small moon discovered in 2012. All five of Pluto's moons are believed to have been formed from a collision between Pluto and another large Kuiper Belt Object billions of years ago.

10. A New Frontier

For the first time in history, a spacecraft is set to visit the Pluto system in 2015. This momentous event marks a major milestone in space exploration, as the spacecraft will be the first to ever explore the mysterious dwarf planet and its five moons. Scientists are eager to learn more about the distant world, and the spacecraft's mission will provide invaluable data about Pluto's composition, atmosphere, and environment.