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Vesta (radius 262.7 ± 0.1 km), the second-largest asteroid, appears to have a differentiated interior and therefore likely was once a dwarf planet, but it is no longer very round today. [74] Pallas (radius 255.5 ± 2 km ), the third-largest asteroid, appears never to have completed differentiation and likewise has an irregular shape.
[1] [2] The low eccentricity and comparatively small size of its orbit give Venus the least range in distance between perihelion and aphelion of the planets: 1.46 million km. The planet orbits the Sun once every 225 days [3] and travels 4.54 au (679,000,000 km; 422,000,000 mi) in doing so, [4] giving an average orbital speed of 35 km/s (78,000 ...
Geosynchronous (and geostationary) orbits have a semi-major axis of 42,164 km (26,199 mi). [10] This works out to an altitude of 35,786 km (22,236 mi). Both complete one full orbit of Earth per sidereal day (relative to the stars, not the Sun). High Earth orbit: geocentric orbits above the altitude of geosynchronous orbit (35,786 km or 22,236 mi).
The period can be in the range from 88 minutes for a very low orbit (a = 6554 km, i = 96°) to 3.8 hours (a = 12 352 km, but this orbit would be equatorial, with i = 180°). A period longer than 3.8 hours may be possible by using an eccentric orbit with p < 12 352 km but a > 12 352 km .
For planet Earth, which can be approximated as an oblate spheroid with radii 6 378.1 km and 6 356.8 km, the mean radius is = (( ) ) / = . The equatorial and polar radii of a planet are often denoted r e {\displaystyle r_{e}} and r p {\displaystyle r_{p}} , respectively.
Radar mosaic of two 65 km (40 mi) wide (and less than 1 km (0.62 mi) high) pancake domes in Venus's Eistla region Much of the Venusian surface appears to have been shaped by volcanic activity. Venus has several times as many volcanoes as Earth, and it has 167 large volcanoes that are over 100 km (60 mi) across.
Venus currently has a surface temperature of 450℃ (the temperature of an oven’s self-cleaning cycle) and an atmosphere dominated by carbon dioxide (96%) with a density 90 times that of Earth’s.
In April 2014, the first measurement of a planet's rotation period was announced: the length of day for the super-Jupiter gas giant Beta Pictoris b is 8 hours (based on the assumption that the axial tilt of the planet is small.) [27] [28] [29] With an equatorial rotational velocity of 25 km per second, this is faster than for the giant planets ...