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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 .
The Earth Similarity Index (ESI) is a proposed characterization of how similar a planetary-mass object or natural satellite is to Earth. It was designed to be a scale from zero to one, with Earth having a value of one; this is meant to simplify planet comparisons from large databases. The scale has no quantitative meaning for habitability.
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]
Diagram of Saturn, to scale. Despite consisting mostly of hydrogen and helium, most of Saturn's mass is not in the gas phase, because hydrogen becomes a non-ideal liquid when the density is above 0.01 g/cm 3, which is reached at a radius containing 99.9% of Saturn's mass. The temperature, pressure, and density inside Saturn all rise steadily ...
These proportionalities may be expressed by the formula: where g is the surface gravity of an object, expressed as a multiple of the Earth's, m is its mass, expressed as a multiple of the Earth's mass (5.976 × 10 24 kg) and r its radius, expressed as a multiple of the Earth's (mean) radius (6,371 km). [9]
Relative masses of the Solar planets. Jupiter at 71% of the total and Saturn at 21% dominate the system. Relative masses of the solid bodies of the Solar System. Earth at 48% and Venus at 39% dominate. Bodies less massive than Pluto are not visible at this scale. Relative masses of the rounded moons of the Solar System.
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 ...
Earth radius (denoted as R 🜨 or R E) is the distance from the center of Earth to a point on or near its surface. Approximating the figure of Earth by an Earth spheroid (an oblate ellipsoid), the radius ranges from a maximum (equatorial radius, denoted a) of nearly 6,378 km (3,963 mi) to a minimum (polar radius, denoted b) of nearly 6,357 km (3,950 mi).