James Glanz
The helium and other elements made by nuclear burning in red giant stars were thought to stay bottled up deep inside the stars, but observers have noticed that some of this ash leaks to the stellar surface. A new set of calculations now shows that the ash makes the giants brighter than expected, which in turn casts doubt on a whole set of assumptions that had pegged the age of the oldest stars at 15 billion years--substantially older than other benchmarks of cosmic age.