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Herschel underestimated its diameter at 260 km (160 mi) in 1802; in 1811, German astronomer Johann Hieronymus Schröter overestimated it as 2,613 km (1,624 mi). [25] In the 1970s, infrared photometry enabled more accurate measurements of its albedo, and Ceres's diameter was determined to within ten per cent of its true value of 939 km (583 mi).
The surface of Ceres has a large number of craters with low relief, indicating that they lie over a relatively soft surface, probably of water ice. Kerwan crater is extremely low relief, with a diameter of 283.88 kilometers, reminiscent of large, flat craters on Tethys and Iapetus. It is distinctly shallow for its size, and lacks a central peak ...
This list contains a selection of objects 50 and 99 km in radius (100 km to 199 km in average diameter). The listed objects currently include most objects in the asteroid belt and moons of the giant planets in this size range, but many newly discovered objects in the outer Solar System are missing, such as those included in the following ...
Diameter (km) Discovered Spacecraft Year(s) Closest approach (km) Closest approach (asteroid radii) Notes Landmark(s) 1 Ceres: 939.4: January 1, 1801: Dawn: 2014–present: 375: 0.80: Dawn took its first "close up" picture of Ceres in December 2014, and entered orbit in March 2015: First likely dwarf planet visited by a spacecraft, largest ...
Ceres, at 950 km in diameter, is close to equilibrium, but some deviations from equilibrium shape remain unexplained. [14] Much larger objects, such as Earth's moon and the planet Mercury, are not near hydrostatic equilibrium today, [ 15 ] [ 16 ] [ 17 ] though the Moon is composed primarily of silicate rock and Mercury of metal (in contrast to ...
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.
Models based on the formation of the current asteroid belt had suggested Ceres should possess 10 to 15 craters larger than 400 km (250 mi) in diameter. [91] The largest confirmed crater on Ceres, Kerwan Basin, is 284 km (176 mi) across. [92] The most likely reason for this is viscous relaxation of the crust slowly flattening out larger impacts ...
In early 2014, using data from the Herschel Space Observatory, it was discovered that there are several localized (not more than 60 km in diameter) mid-latitude sources of water vapor on Ceres, which each give off about 10 26 molecules (or 3 kg) of water per second. Two potential source regions, designated Piazzi (123°E, 21°N) and Region A ...