We don't call 'em "strange", dude... We say they have "alternative lifestyles". Get it straight.
What is Isotopically Strange Xenon?
"Isotopically strange xenon (ISX) is strongly enriched in the p- and r-isotopes relative to solar and terrestrial xenon..."
So it's an isotope. I dunno what p- and r- refer to. Chemist-freak talk.
It has to do with isotope ratios. Xe has nine naturally occuring isotopes, with masses from 124, 126, 128, 129, 130, 131, 132, 134, and 136 Daltons. The ratio of these isotopes' occurence depends on the nuclear reactions going on in the star to form the Xe.
The different types have to do with the different chains of nuclear reactions leading to certain distributions of isotopes...
So, alternative lifestyle Xenon learns it from its parent nuclei. Remember this when other elements try to legalize unusual reaction pathways...