Radioactive decay dating
Meteorites are among the oldest objects we know about - formed about 4.5 billion years ago. This article describes the principles and methods used to make that determination.There are well-known methods of finding the ages of some natural objects.
Actually, meteorites that formed by melting, e.g., the various types of achondrites, usually give more precise ages.
Thus, although "extinct", these nuclides are present in meteorites, but produced by a more recent process.
"The idea that Rb-Sr is the most used chronometer for meteorites is largely based on work done 10-30 years ago.
After the second half-life has elapsed, yet another 50% of the remaining parent isotope will decay into daughter isotopes, and so on.
For all practical purposes, the original isotope is considered extinct after 6 half-life intervals. A small portion of a meteorite is vaporized in the device forming ions.