A hint of normality at last?

摘要

The chemical abundances of the oldest stars in the Galaxy hold a key to what the Universe's conditions were like at the earliest times. Indeed, the three most chemically primitive stars currently known have abundance patterns extremely different from those formed after the Universe's first billion years - for example, their abundance ratio of carbon to iron is about 10-1,000 times larger than is found at later times, indicating quite different conditions between the two epochs. On page 67 of this issue, Caffau et aV report a chemically primitive star that is in some respects more 'normal' than these objects, indicating a larger chemical diversity, which challenges our understanding of the first stars.