Mapping the family tree of stars

February 20, 2017 by Paul Seagrove
Image showing family trees of stars in our galaxy, including the Sun. Credit: Institute of Astronomy

Astronomers are borrowing principles applied in biology and archaeology to build a family tree of the stars in the galaxy. By studying chemical signatures found in the stars, they are piecing together these evolutionary trees looking at how the stars formed and how they are connected to each other. The signatures act as a proxy for DNA sequences. It's akin to chemical tagging of stars and forms the basis of a discipline astronomers refer to as Galactic archaeology.

It was Charles Darwin, who, in 1859 published his revolutionary theory that all life forms are descended from one common ancestor. This theory has informed evolutionary biology ever since but it was a chance encounter between an astronomer and an biologist over dinner at King's College in Cambridge that got the astronomer thinking about how it could be applied to stars in the Milky Way.

Writing in Monthly Notices of the Royal Astronomical Society, Dr Paula Jofré, of the University of Cambridge's Institute of Astronomy, describes how she set about creating a phylogenetic "tree of life" that connects a number of stars in the galaxy.

"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" she says.

The team picked twenty-two stars, including the Sun, to study. The chemical elements have been carefully measured from data coming from ground-based high-resolution spectra taken with large telescopes located in the north of Chile. 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 precursor of Gaia, the spacecraft orbiting Earth that was launched by the European Space Agency and is almost halfway through a 5-year project to map the sky.

Stars are born from violent explosions in the gas clouds of the galaxy. Two stars with the same chemical compositions are likely to have been born in the same molecular cloud. Some live longer than the age of the solar system and serve as fossil records of the composition of the gas at the time they were formed. The oldest star in the sample analysed by the team is estimated to be almost ten billion years old, which is twice as old as the Sun. The youngest is 700 million years old.

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 , 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", says Professor Robert Foley, of the Leverhulme Centre for Human Evolutionary Studies at Cambridge.

With an increasing number of datasets being made available from both Gaia and more advanced telescopes on the ground, and on-going and future large spectroscopic surveys, astronomers are moving closer to being able to assemble one tree that would connect all the in the Milky Way.

Paula Jofré et al. 'Cosmic phylogeny: reconstructing the chemical history of the solar neighbourhood with an ' is published by Monthly Notices of the Royal Astronomical Society.

Explore further: Stars in the halo of the Milky Way often travel in groups

More information: Paula Jofré et al. Cosmic phylogeny: reconstructing the chemical history of the solar neighbourhood with an evolutionary tree, Monthly Notices of the Royal Astronomical Society (2017). DOI: 10.1093/mnras/stx075

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7 comments

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RNP
5 / 5 (1) Feb 20, 2017
Wow! A fascinating, novel and almost cross-disciplinary approach to galactic archaeology. Great paper, open access version of which is available here: https://arxiv.org...2575.pdf
El_Nose
5 / 5 (1) Feb 20, 2017
so sorry - haven't made it to the article yet - the caption on the picture brought me to a standstill -- Image showing family trees of stars in our solar system, including the Sun. Credit: Institute of Astronomy

So since we only have one star in our solar system my mind screamed stop!!

Okay probably copied from the source that way-- i hope because the first sentence in the first paragraph would have been better.
cantdrive85
1.7 / 5 (6) Feb 20, 2017
The draw back to this approach is of course it is based upon an edifice of speculation. The chemical signatures may have absolutely no relationships to the age of the stars. This "family tree" may be for more useless than a daily horoscope.
FredJose
1.6 / 5 (7) Feb 21, 2017
Well, what can I say - people want the evolutionary god to be omnipotent so have to include the whole universe.

This idea has the same basic problem that the biological field has - it cannot account for the purely naturalistic origin of the first stars just like the biological field cannot account for the purely naturalistic origin, shape and development of the first life forms. Stars cannot form all by themselves from clouds of gas - the physics doesn't allow it. Neither can biological life pop up into existence all by itself from random chemical processes.

What this research basically wants to do is use pattern analysis to classify stars and presumably planets too at a later stage. Then use the totally useless cladistic diagramming idea to form a tree of "life" for them.

The astronomers/cosmologists will still be in the dark as ever as to where stars come from.
wduckss
3 / 5 (2) Feb 21, 2017

Neither can biological life pop up into existence all by itself from random chemical processes.


Why can not they? Evolution exactly shows that this sequence of events the primary. If there is no "random" of chemical processes, how do you explain the complex structure of the body that arises from the of association of particles. The gas is mostly hydrogen and some helium, other traces, all bodies are complex chemical composition (see the composition of the earth, etc.).
antialias_physorg
5 / 5 (4) Feb 21, 2017
it cannot account for the purely naturalistic origin of the first stars just like the biological field cannot account for the purely naturalistic origin

Since the origin of stars is not part of the study of evolution of stars - what's your point?
Since the origin of life is not the part of the biological theory of evolution - what's your point?

Just admit: you didn't know this. You are faulting theories for things that they don't apply to.
It looks pretty foolish to attack stuff when you demonstrably don't know what you're talking about.

What this research basically wants to do is use pattern analysis to classify stars and presumably planets too at a later stage. Then use the totally useless cladistic diagramming idea to form a tree of "life" for them.

All this article is about is: They are using the same type of graph that biologists use. End of story. Nothing more. Nothing less.
wduckss
1 / 5 (1) Feb 21, 2017


All this article is about is: They are using the same type of graph that biologists use. End of story. Nothing more. Nothing less.


@antialias_physorg
They are completely wrong and that is the point. Do not mix diagrams for elephants and average rainfall.
FredJose I am give an A. for the rest, I had no need for comment after his comments.
If you object Fred must use arguments and evidence. It did not say someone is, that ...
Author (s) are instead evidence tried to sell the story, who is smoking it is his problem.

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