Tiny Stardust with a Big Story: Strontium Clues from Exploding Stars

This paper reports the discovery of tiny presolar graphite subgrains with strong excesses of the p-process isotope ⁸⁴Sr. The measurements rule out low-mass AGB stars and instead point to core-collapse supernovae as the source. Small-scale mixing between inner, oxygen-rich layers and outer, carbon-rich regions of exploding massive stars best explains the observations, providing the first direct evidence that core-collapse supernovae produce p-process isotopes.