Pluto

Pluto is a dwarf planet in the outer part of the solar-system. It lies in a region called the Kuiper Belt, which is a zone of icy bodies and small objects beyond the orbit of neptune. Pluto was discovered in 1930 by an American astronomer named Clyde Tombaugh. For many years, it was known as the ninth planet from the sun, but in 2006, scientists reclassified it as a dwarf planet because of its small size and the way it shares its orbit with other objects.

Pluto is much smaller than earth and even smaller than Earth's moon. It has a diameter of about 2,377 kilometers. Its surface is covered with ice made of nitrogen, methane, and carbon monoxide. Because it is so far from the Sun, Pluto is extremely cold, with temperatures around −230°C. The sunlight that reaches Pluto is about 1,000 times weaker than on Earth, so it appears dim even during its day.

Pluto moves in an oval-shaped, or elliptical, orbit that is tilted compared to the other planets. This means that sometimes it is closer to the Sun than Neptune, but most of the time it is farther away. One orbit around the Sun takes Pluto about 248 Earth years. A single day on Pluto—one full rotation—lasts about 6 Earth days and 9 hours.

Pluto has five known moons. The largest moon is Charon, which is so big compared to Pluto that the two bodies are sometimes called a double dwarf planet system. The other moons are Styx, Nix, Kerberos, and Hydra. Charon and Pluto are tidally locked, meaning the same sides always face each other as they rotate and orbit together.

The surface of Pluto shows mountains, plains, and large frozen areas. One large plain called Sputnik Planitia is made of frozen nitrogen and may cover an ocean of liquid water deep below. The planet’s thin atmosphere expands when Pluto moves closer to the Sun and freezes again as it moves farther away.

In 2015, NASA’s New Horizons spacecraft flew past Pluto, giving scientists their first detailed pictures of this distant world. The mission revealed that Pluto is geologically active and more complex than expected. Today, Pluto remains an important object of study because it helps scientists learn about the formation of the Solar System and icy bodies in the outer space.