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Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most- massive known object to directly orbit the Sun .
Pluto is a dwarf planet with mountains, valleys, plains, craters, and glaciers. Learn about its discovery, reclassification, exploration, and more from NASA's official website.
Introduction. Pluto is a complex and mysterious world with mountains, valleys, plains, craters, and glaciers. It is located in the distant Kuiper Belt. Discovered in 1930, Pluto was long considered our solar system's ninth planet.
- Overview
- Basic astronomical data
In 2006 the International Astronomical Union (IAU) removed Pluto from the list of planets and classified it as a dwarf planet because of its small size, icy composition, and anomalous orbital characteristics. The IAU adopted this category to recognize the larger and more massive members with similar compositions and origins occupying the same orbital “neighborhood.”
Who discovered Pluto?
Amateur American astronomer Clyde Tombaugh found Pluto in the constellation Gemini on February 18, 1930.
How far is Pluto from Sun?
Pluto’s mean distance from the Sun is about 5.9 billion km (3.7 billion miles or 39.5 astronomical units).
Is Pluto's orbit circular or eccentric?
Pluto’s mean distance from the Sun, about 5.9 billion km (3.7 billion miles or 39.5 astronomical units), gives it an orbit larger than that of the outermost planet, Neptune. (One astronomical unit [AU] is the average distance from Earth to the Sun—about 150 million km [93 million miles].) Its orbit, compared with those of the planets, is atypical in several ways. It is more elongated, or eccentric, than any of the planetary orbits and more inclined (at 17.1°) to the ecliptic, the plane of Earth’s orbit, near which the orbits of most of the planets lie. In traveling its eccentric path around the Sun, Pluto varies in distance from 29.7 AU, at its closest point to the Sun (perihelion), to 49.5 AU, at its farthest point (aphelion). Because Neptune orbits in a nearly circular path at 30.1 AU, Pluto is for a small part of each revolution actually closer to the Sun than is Neptune. Nevertheless, the two bodies will never collide, because Pluto is locked in a stabilizing 3:2 resonance with Neptune; i.e., it completes two orbits around the Sun in exactly the time it takes Neptune to complete three. This gravitational interaction affects their orbits such that they can never pass closer than about 17 AU. The last time Pluto reached perihelion occurred in 1989; for about 10 years before that time and again afterward, Neptune was more distant than Pluto from the Sun.
Observations from Earth have revealed that Pluto’s brightness varies with a period of 6.3873 Earth days, which is now well established as its rotation period (sidereal day). Of the planets, only Mercury, with a rotation period of almost 59 days, and Venus, with 243 days, turn more slowly. Pluto’s axis of rotation is tilted at an angle of 120° from the perpendicular to the plane of its orbit, so that its north pole actually points 30° below the plane. (By convention, above the plane is taken to mean in the direction of Earth’s and the Sun’s north poles; below, in the opposite direction. For comparison, Earth’s north polar axis is tilted 23.5° away from the perpendicular, above its orbital plane.) Pluto thus rotates nearly on its side in a retrograde direction (opposite the direction of rotation of the Sun and most of the planets); an observer on its surface would see the Sun rise in the west and set in the east.
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Dwarf planet Pluto is a member of a group of objects that orbit in a disc-like zone beyond the orbit of Neptune called the Kuiper Belt. This distant realm is populated with thousands of miniature icy worlds, which formed early in the history of our solar system about 4.5 billion years ago.
Jun 13, 2024 · Learn about Pluto, the dwarf planet in the Kuiper Belt, and its moon Charon. Find out why Pluto is not a planet, how it orbits the Sun, and what NASA's New Horizons spacecraft discovered there.
Learn about Pluto's discovery, reclassification, moons, surface, atmosphere, and more. Find out how Pluto compares to other planets and moons in size, mass, and orbit.
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