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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.
Type 2 chondrites are those that have experienced extensive aqueous alteration, but still contain recognizable chondrules as well as primary, unaltered olivine and/or pyroxene. The fine-grained matrix is generally fully hydrated and minerals inside chondrules may show variable degrees of hydration.
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 ]
Aqueous alteration promotes a composition of hydrous phyllosilicates, magnetite, and olivine crystals occurring in a black matrix, and a possible lack of chondrules. It is thought they have not been heated above 50 °C (122 °F), indicating that they condensed in the cooler outer portion of the solar nebula.
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 ...
Ordinary chondrite NWA 3189 sliced. Field of view c. 2.2 cm across. NWA 3189 has been classified as an LL3.2–3.4 ordinary chondrite ("LL" means very low total iron content; "3" refers to well-preserved chondrules – the rock has not been subjected to metamorphism intense enough to disrupt the chondritic texture).
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.
Lyman alpha nebulae around quasars can have sizes between 15 kpc and 460 kpc. [1] Especially large Enormous Lyα nebula (ELAN) can have large sizes of ≳100 kpc. [2] Farina et al. 2019 table 5 has an extensive compilation of Lyman alpha nebulae around quasars. [1] For now this list contains only the largest ELANs, with sizes larger than 300 kpc.