Question: Hi, I am trying to establish whether each star has a unique signature. I asked an astronomer locally (Keilder telescope) and he says they do all have signatures, but he cannot say for sure they are unique although he has never encountered a duplicate. Our family (2 sons at University) are trying to find the answer as a family work together project. Can you help us? — Tony
Answer: The abundances of elements in a star produce the chemical or spectral “signature” that we use to help classify different types of stars. Because how that chemical signature looks depends upon the relative abundances of different atomic elements in the star, this would suggest that different stars can have different chemical signatures. Looking at it a different way, I believe that the likelihood of any two stars having the exact same elemental abundances is pretty small, so in practice stars have unique chemical signatures.