using, Gemini high-resolution optical spectrometer (GHOST). 8.1 m Gemini South Telescope At Cerro Pachon, Chile, astronomers explored different scenarios to explain chemical differences found in a remarkable giant-giant binary star system. HD 138202 + CD-30 12303.
Artist impressions of HD 138202 + CD-30 12303. This is a binary pair of giant stars located 1,707 light-years away from her in the constellation Lupus. Image credits: NOIRLab / NSF / AURA / J. da Silva, Spaceengine / M. Zamani.
It is estimated that up to 85% of stars exist in binary systems, some even containing three or more stars.
Because these pairs of stars are born together from the same molecular cloud of shared, rich chemical constituents, astronomers would expect them to have nearly identical compositions and planetary systems. However, this is not the case for many binaries.
Some proposed explanations hold that these differences are events that occurred after the stars evolved, but astronomers using the GHOST instrument believe that these differences are actually caused by stars forming. We have confirmed that this may have occurred even before it started.
“GHOST's extremely high-quality spectra provide unprecedented resolution, allowing us to determine star parameters and chemical abundances with the highest possible precision,” said Dr. Carlos Safé, an astronomer at the Institute of Astronomy, Earth and Space Sciences (ICATE). Now we can measure it.” -Koniset).
“These measurements reveal that some stars have higher abundances of heavy elements than others.”
“We used a unique approach to uncover the cause of this discrepancy.”
Previous studies have proposed three possible explanations for the observed chemical differences between binaries.
Two of them involve processes that occur long before a star's evolution. The diffusion of atoms, or the precipitation of chemical elements into gradient layers depending on each star's temperature and surface gravity. Small rocky planets could then be engulfed, leading to chemical changes in the star's composition.
A third possible explanation looks back to the beginning of star formation and suggests that the differences stem from primordial or pre-existing heterogeneous regions within the molecular cloud.
More simply, if a molecular cloud has an uneven distribution of chemical elements, then stars born in that cloud will have different compositions depending on the elements available where they formed. It will be.
Previous research has concluded that all three explanations are possible. However, these studies focused only on main-sequence binaries.
The main sequence is the stage in which stars spend most of their existence, and most stars in the universe, including the Sun, are main sequence stars.
Instead, Dr. Safeh and his colleagues observed HD 138202 + CD-30 12303, a binary system consisting of two giant stars.
These stars have a very deep and highly turbulent outer layer, or convective zone.
The properties of these thick convective zones allowed the research team to rule out two of three possible explanations.
The constant swirling of fluid within the convective zone makes it difficult for material to settle into layers, meaning that giant stars are less susceptible to atomic diffusion, ruling out the first explanation.
The thick outer layer also means that engulfing the planet does not change the star's composition much because the ingested material dilutes quickly, ruling out the second explanation.
This leaves primordial heterogeneity within the molecular cloud as a confirmed explanation.
“This is the first time that astronomers have been able to confirm that differences between binary stars begin early in their formation,” Dr. Safet said.
of findings It was published in the magazine Astronomy and Astrophysics Letters.
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C. Safe other. 2024. Unraveling the origins of chemical differences using GHOST. A&A 682, L23; doi: 10.1051/0004-6361/202449263
Source: www.sci.news
