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Most meteoritic calcium-rich, aluminum-rich inclusions (CAIs) formed from areservoir with ${}^{26}{\rm Al}/{}^{27}{\rm Al} \approx 5 \times 10^{-5}$, butsome record lower $({}^{26}{\rm Al}/{}^{27}{\rm Al})_0$, demanding they sampleda reservoir without live ${}^{26}{\rm Al}$. This has been interpreted asevidence for "late injection" of supernova material into our protoplanetarydisk. We instead interpret the heterogeneity as chemical, demonstrating thatthese inclusions are strongly associated with the refractory phases corundum orhibonite. We name them "Low-${}^{26}{\rm Al}/{}^{27}{\rm Al}$ Corundum/HiboniteInclusions" (LAACHIs). We present a detailed astrophysical model for LAACHIformation in which they derive their Al from presolar corundum, spinel orhibonite grains $0.5 - 2 \, \mu{\rm m}$ in size with no live ${}^{26}{\rm Al}$;live ${}^{26}{\rm Al}$ is carried on smaller ($<$50 nm) presolar chromiumspinel grains from recent nearby Wolf-Rayet stars or supernovae. In hot($\approx$ 1350-1425 K) regions of the disk these grains, and perovskitegrains, would be the only survivors. These negatively charged grains would growto sizes $1 - 10^3 \, \mu{\rm m}$, even incorporating positively chargedperovskite grains, but not the small, negatively charged ${}^{26}{\rmAl}$-bearing grains. Chemical and isotopic fractionations due to grain chargingwas a significant process in hot regions of the disk. Our model explains thesizes, compositions, oxygen isotopic signatures, and the large, correlated${}^{48}{\rm Ca}$ and ${}^{50}{\rm Ti}$ anomalies (if carried by presolarperovskite) of LAACHIs, and especially how they incorporated no ${}^{26}{\rmAl}$ in a solar nebula with uniform, canonical ${}^{26}{\rm Al}/{}^{27}{\rmAl}$. A late injection of supernova material is obviated, although formation ofthe Sun in a high-mass star-forming region is demanded.

Origin of Low-${}^{26}{\rm Al}/{}^{27}{\rm Al}$ Corundum/Hibonite Inclusions in Meteorites