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A size comparison of Neptune and Earth. Neptune's mass of 1.0243 × 10 26 kg [8] is intermediate between Earth and the larger gas giants: it is 17 times that of Earth but just 1/19th that of Jupiter. [g] Its gravity at 1 bar is 11.15 m/s 2, 1.14 times the surface gravity of Earth, [71] and surpassed only by Jupiter. [72]
Terrestrial planets have a compact, rocky surfaces, and Venus, Earth, and Mars each also has an atmosphere. Their size, radius, and density are all similar. Terrestrial planets have numerous similarities to dwarf planets (objects like Pluto), which also have a solid surface, but are primarily composed of icy materials.
There are large variations in surface temperature over space and time on airless or near-airless bodies like Mars, which has daily surface temperature variations of 50–60 K. [18] [19] Because of a relative lack of air to transport or retain heat, significant variations in temperature develop. Assuming the planet radiates as a blackbody (i.e ...
The size of solid bodies does not include an object's atmosphere. For example, Titan looks bigger than Ganymede, but its solid body is smaller. For the giant planets , the "radius" is defined as the distance from the center at which the atmosphere reaches 1 bar of atmospheric pressure.
The choice of solar mass, M ☉, as the basic unit for planetary mass comes directly from the calculations used to determine planetary mass.In the most precise case, that of the Earth itself, the mass is known in terms of solar masses to twelve significant figures: the same mass, in terms of kilograms or other Earth-based units, is only known to five significant figures, which is less than a ...
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 ...
Relative masses of the terrestrial planets of the Solar System, and the Moon (shown here as Luna) The inner planets (sizes to scale). From left to right: Earth, Mars, Venus and Mercury. The Solar System has four terrestrial planets under the dynamical definition: Mercury, Venus, Earth and Mars.
The eight planets of the Solar System with size to scale (up to down, left to right): Saturn, Jupiter, Uranus, Neptune (outer planets), Earth, Venus, Mars, and Mercury (inner planets) A planet is a large, rounded astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. [1]