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Ca-Al-rich inclusions (CAIs) are centimeter-sized light-coloured calcium and aluminium rich inclusions found in carbonaceous chondrites. CAIs contains high-temperature minerals and are among the first solids which solidified from the cooling protoplanetary disk. CAIs were formed at much higher temperatures than the associated chondrules, and may have survived many high-temperature events, whereas most chondrules are the product of a single transient melting event.
The isotopic anomalies of CAIs give valuable clues about the solar system's formation, suggesting that the solar nebula collapsed shortly after a nearby supernova. Radiometric dating shows that the CAIs formed about 2 million years before the chondrules formed.
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