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Chondrules in the chondrite classification Grassland. A millimeter scale is shown. Chondrules in the Carbonaceous Chondrite NWA 13887. A chondrule (from Ancient Greek χόνδρος chondros, grain) is a round grain found in a chondrite. Chondrules form as molten or partially molten droplets in space before being accreted to their parent asteroids.
Chondrules, metal grains, and other components likely formed in the solar nebula. These accreted together to form parent asteroids. These accreted together to form parent asteroids. Some of these bodies subsequently melted, forming metallic cores and olivine -rich mantles ; others were aqueously altered. [ 35 ]
Their chondrules are generally in the range of 0.5 to 1 mm in diameter. Ordinary chondrites are distinguished chemically by their depletions in refractory lithophile elements, such as Ca, Al, Ti, and rare earths , relative to Si, and isotopically by their unusually high 17 O/ 16 O ratios relative to 18 O/ 16 O compared to Earth rocks.
While CM chondrules are smaller than average in diameter (~300 micrometer), CO chondrules are exceptionally small (~170 um). [ 31 ] [ 32 ] This may be a survivor bias : consider that the water which dissolves CM chondrules successfully eliminates those which are already small, while those which were large may remain to be observed, though with ...
The main petrologic characteristic of Type 1 chondrites, such as CIs, is the lack of recognizable chondrules, thus excepting the sample from Tagish Lake. Yet small chondrule fragments and calcium–aluminium-rich inclusions (CAIs) do occur, but are quite rare.
EH (high-iron) chondrites contain small chondrules (~0.2 millimetres (0.0079 in)) and high ratios of siderophile elements to silicon. Somewhat more than 10% of the rock is composed of metal grains. A diagnostic feature of EH chondrites is that the Fe-Ni metal contains ~3 wt% elemental silicon.
NGC 3132 (also known as the Eight-Burst Nebula, [2] the Southern Ring Nebula, [2] or Caldwell 74) is a bright and extensively studied planetary nebula in the constellation Vela. Its distance from Earth is estimated at 613 pc or 2,000 light-years .
It was discovered on 1 August 1826 by Scottish astronomer James Dunlop. [6] It is embedded in a nebula known as N90. Radiation and shock waves from the stars of NGC 602 have pushed away much of the lighter surrounding gas and dust that is N90, and this in turn has triggered new star formation in the ridges (or " elephant trunks ") of the nebula.