The stellar origin of many elements
Claim in the list: Heavy elements (iron, calcium, carbon) form inside stars and during supernova explosions—we are made of stardust.
Verification: Broadly supported, but origins differ by element and process. Carbon is produced mainly in stars; iron and calcium are also made through stellar processes and supernova explosions. Elements heavier than iron have additional sources, including neutron-star mergers. Hydrogen and much of the helium formed in the early universe. Stellar winds and explosions disperse synthesized elements into interstellar space, where they can become part of later stars, planets, and organisms. “Stardust” is figurative language.
Conclusion: Many atoms in Earth and human bodies were synthesized by earlier generations of stars and dispersed through space, but not every element forms only in supernovae.