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Makemake has one moon, discovered in April 2016. A number of other objects in the Kuiper belt and scattered disk may turn out to be dwarf planets. Orcus, Quaoar, Gonggong, and Sedna are generally agreed to be dwarf planets among astronomers, and all but Sedna are known to have moons. [9]
The sizes and masses of many of the moons of Jupiter and Saturn are fairly well known due to numerous observations and interactions of the Galileo and Cassini orbiters; however, many of the moons with a radius less than ~100 km, such as Jupiter's Himalia, have far less certain masses. [5]
However, there has been disagreement on the required size. Early speculations were based on the small moons of the giant planets, which attain roundness around a threshold of 200 km radius. [49] However, these moons are at higher temperatures than TNOs and are icier than TNOs are likely to be.
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 ...
Uranus has five major moons: Miranda, Ariel, Umbriel, Titania, and Oberon. They range in diameter from 472 km for Miranda to 1578 km for Titania. [21] All these moons are relatively dark objects: their geometrical albedo varies between 30 and 50%, whereas their Bond albedo is between 10 and 23%. [25] Umbriel is the darkest moon and Ariel the ...
An annotated picture of some of Neptune's many moons as captured by the James Webb Space Telescope. The bright blue diffraction star is Triton, Neptune's largest moon; while Hippocamp, its smallest regular moon, is too small to be seen. The planet Neptune has 16 known moons, which are named for minor water deities and a water creature in Greek ...
Montage of planets and some moons that the two Voyager spacecraft have visited and studied. It is the only program that visited all four outer planets. A total of nine spacecraft have been launched on missions that involve visits to the outer planets; all nine missions involve encounters with Jupiter, with four spacecraft also visiting Saturn.
It is slightly more massive than the second most massive moon, Saturn's satellite Titan, and is more than twice as massive as the Earth's Moon. It is larger than the planet Mercury, which has a diameter of 4,880 kilometres (3,030 mi) but is only 45 percent of Mercury's mass. Ganymede is the ninth-largest object in the solar system, but the ...