Interstellar matter formed in a supernova has been discovered on Earth now for the first time.
Light coming to Earth from distant supernovas is recorded all the time.
Likewise, a dozen or so neutrinos from nearby Supernova 1987A have been detected. But atoms from supernovas are a different matter. In a sense, all the heavy atoms on Earth have been processed through or created in supernovas long ago and far away. But now comes evidence of atoms from a supernova that may have been deposited here only a few million years ago. First, several sediment layers were dated, and only then were samples scrutinized with accelerator mass spectroscopy, needed to spot the faintly-present iron.