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This is smaller than the largest natural satellite that is known not to be gravitationally rounded, Neptune VIII Proteus (radius 210 ± 7 km). Several of these were once in equilibrium but are no longer: these include Earth's moon [77] and all of the moons listed for Saturn apart from Titan and Rhea. [55]
The Saturn-mass planet HD 149026 b has only two-thirds of Saturn's radius, so it may have a rock–ice core of 60 Earth masses or more. [39] CoRoT-20b has 4.24 times Jupiter's mass but a radius of only 0.84 that of Jupiter; it may have a metal core of 800 Earth masses if the heavy elements are concentrated in the core, or a core of 300 Earth ...
During the 1970s to 1980s, the increasing number of artificial satellites in Earth orbit further facilitated high-precision measurements, and the relative uncertainty was decreased by another three orders of magnitude, to about 2 × 10 −9 (1 in 500 million) as of 1992. Measurement involves observations of the distances from the satellite to ...
Parts-per-million chart of the relative mass distribution of the Solar System, each cubelet denoting 2 × 10 24 kg. This article includes a list of the most massive known objects of the Solar System and partial lists of smaller objects by observed mean radius. These lists can be sorted according to an object's radius and mass and, for the most ...
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 ...
The astronomical unit of length is known as the astronomical unit (A or au), which in the IAU(1976) system is defined as the length for which the gravitational constant, more specifically the Gaussian gravitational constant k expressed in the astronomical units (i.e. k 2 has units A 3 S −1 D −2), takes the value of 0.017 202 098 95. This ...
From the value of the diurnal parallax, one can determine the distance to the Sun from the geometry of Earth. [6] [7] The first known estimate of the solar mass was by Isaac Newton. [8] In his work Principia (1687), he estimated that the ratio of the mass of Earth to the Sun was about 1 ⁄ 28 700. Later he determined that his value was based ...
The eccentricity of an elliptical orbit can be used to obtain the ratio of the apoapsis radius to the periapsis radius: = (+) = + For Earth, orbital eccentricity e ≈ 0.016 71 , apoapsis is aphelion and periapsis is perihelion, relative to the Sun.