Research Article
Revisiting Oxygen Production Pathways: 16O Abundances in 34 Metal-Poor Stars
Issue:
Volume 13, Issue 1, March 2026
Pages:
1-14
Received:
10 December 2025
Accepted:
23 December 2025
Published:
4 February 2026
DOI:
10.11648/j.ajaa.20261301.11
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Abstract: We investigate how the oxygen isotope 16O is produced in metal-poor stars and whether current nuclear reaction models can explain the oxygen abundances observed in such stars. Our study focuses on proton- and α-capture reactions operating within the Carbon–Oxygen–Fluorine (COF) nuclear reaction chain, using updated reaction rates from recent nuclear physics compilations. Oxygen abundances are calculated under representative stellar conditions and compared with observational measurements for a sample of 34 metal-poor halo and thick-disk stars taken from the literature. The results show that there exists a limited range of stellar temperatures for which the calculated oxygen abundances closely match the observed values. At relatively low temperatures, the oxygen abundance remains nearly constant, indicating that oxygen production and destruction are both inefficient. As the temperature increases beyond about 0.15 GK, oxygen production becomes more effective, leading to an increase in the predicted oxygen abundance. At still higher temperatures, competing nuclear reactions reduce the net amount of oxygen produced, causing the abundance to decline. A statistical comparison between the calculated and observed oxygen abundances shows a strong agreement, with a correlation coefficient of r = 0.89. For most stars, the differences between predicted and observed values are small and lie within the uncertainties expected from spectroscopic measurements. The few cases where larger differences are found can be explained by observational uncertainties and stellar mixing processes. Overall, our results indicate that the COF nuclear reaction chain provides a consistent explanation for oxygen production in low-mass, metal-poor stars and plays an important role in shaping the chemical evolution of the early Galaxy.
Abstract: We investigate how the oxygen isotope 16O is produced in metal-poor stars and whether current nuclear reaction models can explain the oxygen abundances observed in such stars. Our study focuses on proton- and α-capture reactions operating within the Carbon–Oxygen–Fluorine (COF) nuclear reaction chain, using updated reaction rates from recent nuclea...
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Review Article
Study of Important Space Missions and Evaluation of Discovering the Astonishing Universe
Khandakar Akhter Hossain*
Issue:
Volume 13, Issue 1, March 2026
Pages:
15-31
Received:
24 December 2025
Accepted:
16 January 2026
Published:
6 February 2026
DOI:
10.11648/j.ajaa.20261301.12
Downloads:
Views:
Abstract: The evaluation of space missions and their influence on the understanding of universe is complicated. They provide both scientific data and insights along with inspire inquisitiveness and fostering a sense of sensation about the cosmos. It has started with the space race of the 20th century, as a result of humans have boarded on a journey through time and space with some of the most groundbreaking and life-changing space missions. NASA’s astrophysics division is dedicated to exploring the universe, pushing the boundaries of what is known of the cosmos, and sharing its discoveries with the world. The division continues growing humanity’s understanding of how the universe began and progressed. NASA researchers are making advancement towards addressing the appealing questions of life in the universe, the early beginnings of the universe, and how it all works with leading-edge technologies and groundbreaking science. The Apollo missions, was a great attempt of courage in human civilization; not only landed humans on the Moon but also brought back samples that helped scientists understand lunar geology and planetary science. The Hubble Space Telescope has revolutionized astronomy, offering fabulous images of distant galaxies and nebulae, and has led to groundbreaking discoveries like the measurement of the universe's expansion rate and the identification of exoplanets. Mars rover missions have advanced our understanding of alien geology and climate, paving the way for future human missions to the red planet. These missions have not only transformed how we see the universe but also describe how we live on earth, contributing to our understanding of the solar system and beyond. Astronomers recently spotted this black hole’s flare-up through XMM-Newton and XRISM’s X-ray technology and noted that it appeared to fade quickly, creating the fast-moving winds. It is a review article to explore and appraise the important space missions on the basis of historical evidence and evaluating the urge of discovering mind set to know the multifaceted cosmology and astonishing Universe.
Abstract: The evaluation of space missions and their influence on the understanding of universe is complicated. They provide both scientific data and insights along with inspire inquisitiveness and fostering a sense of sensation about the cosmos. It has started with the space race of the 20th century, as a result of humans have boarded on a journey through t...
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