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The size and shape of asteroids vary significantly, ranging from small rubble piles under a kilometer across and larger than meteoroids, to Ceres, a dwarf planet almost 1000 km in diameter. A body is classified as a comet, not an asteroid, if it shows a coma (tail) when warmed by solar radiation, although recent observations suggest a continuum ...
The asteroids Bennu and Ryugu have a measured bulk density which suggests that their internal structure is a rubble pile. [ 1 ] [ 2 ] Many comets and most smaller minor planets (<10 km in diameter) are thought to be composed of coalesced rubble.
These are primitive asteroids that may have had their materials chemically altered by liquid water. There are 33 known P-type asteroids. In addition to this, P-type asteroids are thought to be found in the outer asteroid belt and beyond. [8] The distribution of P-type asteroids peaks at an orbital distance of 4 AU. [9]
These are composed primarily of S-type asteroids, whereas the neighboring Hungaria family includes some E-types. [101] The Phocaea family orbit between 2.25 and 2.5 AU from the Sun. [102] Skirting the outer edge of the asteroid belt is the Cybele group, orbiting between 3.3 and 3.5 AU. These have a 7:4 orbital resonance with Jupiter.
Interlopers are asteroids classified as family members based on their so-called proper orbital elements but having spectroscopic properties distinct from the bulk of the family, suggesting that they, contrary to the true family members, did not originate from the same parent body that once fragmented upon a collisional impact.
Stony meteorite – a meteorite composed mostly of silicates. Stony-iron meteorite – a meteorite that is a mixture of meteoric iron and silicates. Strewn field – a field of fragments from one meteorite fall. Structural class – a subdivision of iron meteorites in ataxites, hexahedrites and octahedrites.
Outside the top four, the ranking of all the asteroids is uncertain, as there is a great deal of overlap among the estimates. The largest asteroids with an accurately measured mass, because they have been studied by the probe Dawn, are 1 Ceres with a mass of (939.3 ± 0.5) × 10 18 kg, and 4 Vesta at (259.076 ± 0.001) × 10 18 kg.
Asteroids as small as 20 metres (66 ft) in diameter can cause significant damage to the local environment and human populations. [5] Larger asteroids penetrate the atmosphere to the surface of the Earth, producing craters if they impact a continent or tsunamis if they impact the sea. Interest in NEOs has increased since the 1980s because of ...