Mapping the stars’ family tree

By taking advantage of techniques used in archaeology and biology, researchers are building a family tree of the galaxy’s stars. Through the observation of chemical signatures, they hope to gain a better understanding of stellar formation and how stars are linked chemically.

Professor Robert Foley, from the University of Cambridge and co-author of the study, said: “The differences between stars and animals are immense, but they share the property of changing over time, and so both can be analysed by building trees of their history.”

Twenty-two stars, including the Sun, were studied by the astronomers. After measuring chemical elements using spectrometry, their evolution was calculated, taking into account age as well as physical motion through space. This data was obtained from Hipparcos, an ESA satellite launched in the late 80s.

Stars have a similar shared parentage as they are derived from gas clouds, and carry that information in their chemical structure. As evolutionary trees can be created in biology, it’s possible to trace a comparable evolution of stars.

Dr Paula Jofré, from Cambridge’s Astronomy Institute and also involved in the study, said: “The use of algorithms to identify families of stars is a science that is constantly under development. Phylogenetic trees add an extra dimension to our endeavours which is why this approach is so special. The branches of the tree serve to inform us about the stars’ shared history.”

The oldest star sample analysed by the team is estimated to be almost 10 billion years old – twice as old as our Sun. The youngest star measured was 700 million years old. With a rising number of datasets available, from both Gaia – Hipparcos’ successor – and advanced ground telescopes, astronomers are confident they’re moving closer to one tree that connects the Milky Way’s stars.

The study was published in Monthly Notices of the Royal Astronomical Society.