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Charon, a moon of Pluto that was proposed as a dwarf planet by the IAU in 2006, is included for comparison. Those objects that have absolute magnitude greater than +1, and so meet the threshold of the joint planet–minor planet naming committee of the IAU, are highlighted, as is Ceres, which the IAU has assumed is a dwarf planet since they ...
Pluto (bottom left) compared in size to the Earth and the Moon. Pluto's diameter is 2 376.6 ± 3.2 km [5] and its mass is (1.303 ± 0.003) × 10 22 kg, 17.7% that of the Moon (0.22% that of Earth). [125] Its surface area is 1.774 443 × 10 7 km 2, or just slightly bigger than Russia or Antarctica (particularly including the Antarctic sea ice ...
Many TNOs are often just assumed to have Pluto's density of 2.0 g/cm 3, but it is just as likely that they have a comet-like density of only 0.5 g/cm 3. [ 4 ] For example, if a TNO is incorrectly assumed to have a mass of 3.59 × 10 20 kg based on a radius of 350 km with a density of 2 g/cm 3 but is later discovered to have a radius of only 175 ...
Pluto was considered a planet up until 2006, when researchers at the International Astronomical Union voted to "demote" it to dwarf planet.
[6] [a] Charon and Pluto are also tidally locked, so that they always present the same face toward each other. The IAU General Assembly in August 2006 considered a proposal that Pluto and Charon be reclassified as a double planet, but the proposal was abandoned. [7] Like Pluto, Charon is a perfect sphere to within measurement uncertainty. [8]
On February 4, 2015, New Horizons entered the Plutonian system, capturing images of Pluto and its moon Charon from about 203,000,000 km (126,000,000 mi) away. From April to June 2015, New Horizons delivered higher-quality images than those from ground telescopes. [10] [11]
It is about half the diameter and an eighth the mass of Pluto, a dwarf planet that resides in a frigid region of the outer Solar System called the Kuiper Belt, beyond the most distant planet Neptune.
Of the inner planets, Mercury and Venus have no natural satellites; Earth has one large natural satellite, known as the Moon; and Mars has two tiny natural satellites, Phobos and Deimos. The giant planets have extensive systems of natural satellites, including half a dozen comparable in size to Earth's Moon: the four Galilean moons , Saturn's ...