Group 4 Dwarf Planets

A dwarf planet, as defined by the International Astronomical Union (IAU), is a celestial body in direct orbit of the Sun[1] that is massive enough that its shape is controlled by gravitational forces rather than mechanical forces.

There are 200 discovered planets in space and i am going to research about three of them.

Pluto, formal designation 134340 Pluto, is the second-most-massive known dwarf planet in the Solar System (after Eris) and the tenth-most-massive body observed directly orbiting the Sun. Originally classified as the ninth planet from the Sun, Pluto was recategorized as a dwarf planet and plutoid due to the discovery that it is only one of several large bodies within the Kuiper belt.[i]

Like other members of the Kuiper belt, Pluto is composed primarily of rock and ice and is relatively small: approximately a sixth the mass of the Earth's Moon and a third its volume. It has an eccentric and highly inclined orbit that takes it from 30 to 49 AU (4.4–7.4 billion km) from the Sun. This causes Pluto to periodically come closer to the Sun than Neptune. As of 2011, it is 32.1 AU from the Sun.[12]

From its discovery in 1930 until 2006, Pluto was classified as a planet. In the late 1970s, following the discovery of minor planet 2060 Chiron in the outer Solar System and the recognition of Pluto's relatively low mass, its status as a major planet began to be questioned.[13] In the late 20th and early 21st centuries, many objects similar to Pluto were discovered in the outer Solar System, notably the scattered disc object Eris in 2005, which is 27% more massive than Pluto.[14] On August 24, 2006, the International Astronomical Union (IAU) defined what it means to be a "planet" within the Solar System. This definition excluded Pluto as a planet and added it as a member of the new category "dwarf planet" along with Eris and Ceres.[15] the reclassification, Pluto was added to the list of minor planets and given the number 134340.[16][17] A number of scientists hold that Pluto should continue to be classified as a planet, and that other dwarf planets should be added to the roster of planets along with Pluto.[18][19]
Pluto has four known moons, the largest being Charon discovered in 1978, along with Nix and Hydra, discovered in 2005,[20] and the provisionally named S/2011 P 1, discovered in 2011.


Ceres, formally 1 Ceres, is the only dwarf planet, and the largest asteroid, in the inner Solar System.[20][21][22] It is a rock–ice body some 950 km (590 mi) in diameter, and though the smallest identified dwarf planet, it constitutes a third of the mass of the asteroid belt.[23][24] Discovered on 1 January 1801 by Giuseppe Piazzi,[25] it was the first asteroid to be identified, though it was classified as a planet at the time.[26] It is named after Ceres, the Roman goddess of growing plants, the harvest, and motherly love.

The Cererian surface is probably a mixture of water ice and various hydrated minerals such as carbonates and clays.[15] It appears to be differentiated into a rocky core and icy mantle,[9] and may harbour an ocean of liquid water under its surface.[27][28] From Earth, the apparent magnitude of Ceres ranges from 6.7 to 9.3, and hence even at its brightest it is still too dim to be seen with the naked eye except under extremely dark skies.[16] The unmanned Dawn spacecraft, launched on 27 September 2007 by NASA, is expected to be the first to explore Ceres after its scheduled arrival there in 2015,[29] after the spacecraft leaves the asteroid 4 Vesta,[30] which it has been orbiting since July 2011.

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