Stars born together have almost identical DNA

The researchers observed the chemical compositions of binary stars in the Milky Way in greater depths than any previous study.

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Using a telescope at McDonald Observatory at the University of Texas at Austin astronomer Keith Hawkins studied the chemistry of twin stars to see if they are identical or fraternal twins. His work, which has been accepted for publication in The Monthly Notices of the Royal Astronomical Society shows that most twin stars are chemically identical, something that could lead to a better understanding of the galaxy’s history over time.

The results have implications that go beyond understanding binary stars.

Many stars are born from a single cloud of dust and gas, and over the course of billions of years, those stars that were born together end up scattered in different parts of the galaxy. However, the analysis of 25 binary stars far apart and identified by the Gaia satellite with the aim of studying their chemical compositions, revealed that twin stars seem to share the chemical DNA of the nucleus.

Using the 2.7-metre Harlan J. Smith telescope at McDonald Observatory, the team got a deeper look at the chemical composition of the 50 stars and discovered that the stars that were born together were virtually identical, something that could help scientists map the history of the Milky Way galaxy.

Hawkins' research into the chemical composition of each of the binary stars is much more thorough than any previous similar study, identifying that stars born that way had a very coincidental chemistry, while stars belonging to the same type, but arbitrarily selected, did not possess that characteristic. In this way, this cosmic clue could help us understand the stars in the Milky Way through chemical labeling and learn which ones were born simultaneously from the same cloud of dust and gas. That’s right, we can use the twin stars to study the antecedents of all the galaxies in our universe, which is certainly disconcerting at best. The value of this work can hardly be overestimated. 

K. Hawkins/UT Austin (data) and NASA/JPL-Caltech/T. Pyle

Stellar nurseries

Astronomers call "large clusters forming single stars," "stellar nurseries," which, Hawkins explained, "scatter over time" (i.e., some millions or even billions of years). But, if chemical labeling is really a reliable concept, astronomers will be able to go back in time to where stars started, by studying their trajectories, as Hawkins put it, "going back over the history of galaxy assembly".

A deeper understanding of the evolution of our Milky Way will provide the basis in order to  understand the building blocks of the universe.

The team is composed of researchers from the University of Texas at Austin, Princeton University, the University of California, Berkeley and the Carnegie Observatories (United States) and was funded by the Research Corporation for Science Advancement.

Reference: The chemical homogeneity of wide binaries from Gaia DR2: arXiv:1912.08895v1 [astro-ph.SR] arxiv.org/abs/1912.08895]

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