The Different Isotopic Compositions of Meteorites

The oldest grains that have been found so far, I think they're about 7 billion years. And what's really cool is we find some grains in meteorites that appear to come from outside our solar system. So how do you date a piece of silicon carbide from an alien solar system? If you analyse anything from Earth that isn't a meteorite, then you look at its isotopic composition. The presolar grains, these interstellar grains, have hugely different isotopic compositions. They are made where you make the isotopes, and that's in giant stars towards the end of their lifetime, and in supernova.