Once the families were identified using the chemical DNA, their evolution was studied with the help of their ages and kinematical properties obtained from the space mission Hipparcos, the spacecraft orbiting Earth that was launched by the European Space Agency (ESA), which is now almost halfway through a 5-year project to map the sky.
They can tell which stars are related based on their chemical makeup, almost like their stellar DNA. If they were born in the same gas cloud then their makeup will be similar. In evolution, organisms are linked together by a pattern of descent with modification as they evolve. Stars are very different from living organisms, but they still have a history of shared descent as they are formed from gas clouds, and carry that history in their chemical structure. By applying the same phylogenetic methods that biologists use to trace descent in plants and animals it is possible to explore the 'evolution' of stars in the Galaxy. The differences between stars and animals is immense, but they share the property of changing over time, and so both can be analysed by building trees of their history.
The team found that the stars they looked at could be plotted on three branches of the tree, with a few miscellaneous ones that didn't fit with the others. This study found 8 of stars they looked at were the Sun's siblings.
'Cosmic phylogeny: reconstructing the chemical history of the solar neighbourhood with an evolutionary tree' by Paula Jofré and others is published by Monthly Notices of the Royal Astronomical Society.
Source references for this article: http://www.seeker.com/astronomers-made-a-family-tree-for-the-stars-in-our-galaxy-2304675063.html
University of Cambridge: Mapping the family tree of stars
New Scientist: Family tree of stars helps reconstruct Milky Way's formation
Monthly Notices of the Royal Astronomical Society: Cosmic phylogeny: reconstructing the chemical history of the solar neighbourhood with an evolutionary tree
Credit for Image at Top of Page:
Treegraphic provided by courtesy of University of Cambridge