5.10. Planets of the Solar System: Pluto: A dwarf planet

5.10. Planets of the Solar System: Pluto: A dwarf planet

Pluto, the ninth and most distant planet in our solar system for nearly a century, was reclassified as a dwarf planet in 2006 by the International Astronomical Union. This decision was made because Pluto does not meet one of the three criteria that the International Astronomical Union uses to define a full-body planet: it must orbit the sun, it must be spherical, and it must have "cleared its orbit" of other debris. Although Pluto meets the first two criteria, it does not meet the third. It resides in the Kuiper Belt, an area full of icy bodies and other "plutos."

Pluto was discovered on February 18, 1930, by American astronomer Clyde Tombaugh at the Lowell Observatory in Arizona. It was named by Venetia Burney, an 11-year-old British girl, who suggested the name after the Roman god of the underworld. This name was approved because Pluto is as dark and remote as the underworld itself.

Pluto is the largest known dwarf planet and the tenth largest body observed directly orbiting the sun. It is larger than the largest object in the asteroid belt, Ceres, but smaller than Triton, Neptune's largest moon. Pluto has five known moons. The largest, Charon, is so large that Pluto and Charon are sometimes referred to as a binary system.

Pluto and Charon are covered with nitrogen ice, but Pluto displays a dark red color due to possible "darkening" of complex organic molecules, while Charon is more gray. Pluto's surface also has mountains, valleys, and even a layer of nitrogen "snow."

Pluto has a tenuous atmosphere composed mainly of nitrogen, with small amounts of methane and carbon monoxide. Pluto's atmosphere has a series of haze layers. The atmosphere extends to about 1,600 km above the planet's surface, making it proportionally higher than Earth's atmosphere.

Pluto's orbit is more oval and more inclined than those of the other planets. This means that at some points Pluto is closer to the sun than Neptune. The last time this happened was from 1979 to 1999. Pluto takes 248 Earth years to complete one orbit around the sun. Its day, or the time it takes to rotate on its axis, lasts 6.4 Earth days.

Pluto's average distance from the sun is about 5.9 billion kilometers. The surface temperature ranges from -375 to -400 degrees Fahrenheit (-225 to -240 degrees Celsius). However, when Pluto is closer to the sun, the surface temperature increases enough that the icy nitrogen sublimates, or turns directly from a solid to a gas, forming a temporary atmosphere.

Pluto has been the focus of much controversy within the scientific community since its reclassification in 2006. Many astronomers still refer to it as the ninth planet in the solar system, and there is an ongoing movement to reclassify it as a full-bodied planet. whole. Regardless of classification, Pluto remains one of the most fascinating bodies in our solar system.

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