Pluto

Pluto, once considered the ninth planet of our solar system, is now classified as a dwarf planet located in the distant Kuiper Belt. Discovered in 1930, it was long regarded as the outermost planet. However, the International Astronomical Union reclassified Pluto as a dwarf planet in 2006, following the discovery of more similar-sized objects in the Kuiper Belt. Pluto has a diameter of approximately 2,374 kilometers, about one-fifth the size of Earth, and a volume of around 1/150th that of Earth. It has five known moons, the largest of which is Charon, which is about half the size of Pluto. Due to its distance from the Sun, Pluto has a very low surface temperature of about -230 degrees Celsius. Its thin atmosphere consists primarily of nitrogen, methane, and carbon monoxide, and it expands and contracts based on its distance from the Sun. Pluto's orbit is unusual, both elliptical and tilted, causing it to sometimes be closer to the Sun than Neptune. Despite no longer being considered a planet, Pluto remains an important object of study for scientists exploring the outer reaches of our solar system and an important milestone in astronomical history.