Pluto
Pluto, once considered the ninth planet from the Sun, is now classified as a dwarf planet. Here are key details about Pluto:
Discovery and Classification
Physical Characteristics
- Pluto has a diameter of approximately 2,377 kilometers, making it roughly one-sixth the size of Earth's moon.
- Its mass is about 1/459th that of Earth's.
- The surface of Pluto is characterized by mountains, valleys, plains, and craters. It has a thin atmosphere composed mostly of nitrogen, with traces of methane and carbon monoxide.
Orbit and Rotation
- Pluto's orbit is highly elliptical and inclined relative to the plane of the Solar System, crossing Neptune's orbit. This unusual orbit can make Pluto closer to the Sun than Neptune for about 20 years out of its 248-year orbit.
- It rotates once every 6.39 Earth days and orbits the Sun in about 248 Earth years.
- Pluto is tidally locked with its largest moon, Charon, meaning one side always faces the moon.
Exploration
- The New Horizons spacecraft, launched by NASA in 2006, flew by Pluto in July 2015, providing the first close-up images and data of the dwarf planet.
- The mission revealed new details about Pluto's geology, atmosphere, and moons.
Moons
- Pluto has five known moons: Charon, Styx, Nix, Kerberos, and Hydra. Charon, being the largest, is also sometimes considered part of a binary system with Pluto.
Cultural Impact
- Named after the Roman god of the underworld, Pluto's name was suggested by an 11-year-old girl, Venetia Burney.
- Pluto has been a source of fascination, appearing in various forms of popular culture, including Disney's character Pluto.
Additional Facts
- Pluto's surface temperature is extremely cold, ranging from -375 to -400 degrees Fahrenheit (-225 to -240 degrees Celsius).
- The IAU defines a dwarf planet as an object that orbits the Sun, has enough mass for its gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, has not cleared its orbital path of other objects, and is not a moon.
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