An abundance of rare isotopes in a planetary nebula

The origin of the chemical elements in the Universe is one of the most fascinating and enduring mysteries in astronomy. Progress so far has come from studies of stars, but here only elemental abundances can be determined reliably. Isotopic ratios are more difficult to obtain. On page 378, Schmidt et al. study the composition of the young planetary nebula K4-47 — a glowing shell of gas and dust that formed from the outer layer of a Sun-like star and that was thrown off during the final stages of the star’s evolution. The authors find that the nebula is unusually enriched in rare isotopes of carbon (13C), nitrogen (15N) and oxygen (17O). The measured composition of K4-47 shows that this object is more enriched in these isotopes than is almost any other nebula or star examined so far.