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For the small outer irregular moons of Uranus, such as Sycorax, which were not discovered by the Voyager 2 flyby, even different NASA web pages, such as the National Space Science Data Center [6] and JPL Solar System Dynamics, [5] give somewhat contradictory size and albedo estimates depending on which research paper is being cited.
Pluto has a moderately eccentric and inclined orbit, ranging from 30 to 49 astronomical units (4.5 to 7.3 billion kilometres; 2.8 to 4.6 billion miles) from the Sun. Light from the Sun takes 5.5 hours to reach Pluto at its orbital distance of 39.5 AU (5.91 billion km; 3.67 billion mi).
Among the other dwarf planets, Ceres has no known moons. It is 90 percent certain that Ceres has no moons larger than 1 km in size, assuming that they would have the same albedo as Ceres itself. [6] Eris has one large known moon, Dysnomia. Accurately determining its size is difficult: one indicative estimate of its radius is 350 ± 57.5 km. [7]
The concept of satellite planets – the idea that all planetary-mass objects, including moons, are planets – is used by some planetary scientists, such as Alan Stern, who are more concerned with whether a celestial body has planetary geology (that is, whether it is a planetary body) than its solar or non-solar orbit (planetary dynamics). [1]
The radii of these objects range over three orders of magnitude, from planetary-mass objects like dwarf planets and some moons to the planets and the Sun. This list does not include small Solar System bodies , but it does include a sample of possible planetary-mass objects whose shapes have yet to be determined.
Thus, the Sun occupies 0.00001% (1 part in 10 7) of the volume of a sphere with a radius the size of Earth's orbit, whereas Earth's volume is roughly 1 millionth (10 −6) that of the Sun. Jupiter, the largest planet, is 5.2 AU from the Sun and has a radius of 71,000 km (0.00047 AU; 44,000 mi), whereas the most distant planet, Neptune, is 30 AU ...
The following is a list of planet types by their mass, orbit, physical and chemical composition, or by another classification. The IAU defines that a planet in the Solar System must orbit around the Sun, has enough mass to assume hydrostatic equilibrium, and has "cleared its neighborhood". The working definition of an exoplanet is as follows ...
An orrery should properly include the Sun, the Earth and the Moon (plus optionally other planets). A model that only includes the Earth, the Moon, and the Sun is called a tellurion or tellurium, and one which only includes the Earth and the Moon is a lunarium. A jovilabe is a model of Jupiter and its moons. [22]