Recently, Delgado-Inglada and collaborators have shown that low-mass (between one and three times the mass of the Sun) planetary nebulae are rich in oxygen, but the standard theoretical models do not predict this. In this work we explain this phenomenon for the first time using theoretical models of nucleosynthesis (production of chemical elements in the interiors of stars) in their precursor AGB stars, which include convective processes, (which transport chemical elements created in the interior to the surface of the star) more efficient than in the standard models. This discovery calls into question the traditional role of planetary nebulae as indicators of metallicity, which is the term used to cover the abundance of the elements which are heavier than hydrogen and helium initially present in the Universe, because now it has been confirmed theoretically that they are intrinsically rich in oxygen. The abundance of oxygen has been used historically to study the differences in the metallicity of our Galaxy and those of other nearby galaxies. In its place, this work confirms that other elements which are not so affected by stellar evolution, such as argon or chlorine should be used as indicators of metallicity. In the future, it will be necessary to use the predictions of these new models to analyse in detail the effect of these oxygen producing stars on the models of chemical evolution of galaxies; in fact they may have an important effect on the characteristic time scales for the formation of the majority of the stars in galaxies.
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The cosmic evolution of the barred galaxy population provides key information about the secular evolution of galaxies and the settling of rotationally dominated discs. We study the bar fraction in the SMACSJ0723.37323 (SMACS0723) cluster of galaxies at z = 0.39 using the Early Release Observations obtained with the NIRCam instrument mounted on the JWST telescope. We visually inspected all cluster member galaxies using the images from the NIRCam F200W filter. We classified the galaxies into ellipticals and discs and determine the presence of a bar. The cluster member selection was based on aAdvertised on
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Massive stars, those over ten times heavier than our Sun, are the conduits of most elements of the periodic table and drive the morphological and chemical makeup of their host galaxies. Yet the origin of the most luminous and hottest stars among them, called 'blue supergiants', has been debated for many decades. Blue supergiants are strange stars. First, they are observed in large numbers, despite conventional stellar physics expecting them to live only briefly. Second, they are typically found alone, despite most massive stars being born with companions. Third, the majority of them harbourAdvertised on
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In the 90s, the COBE satellite discovered that not all the microwave emission from our Galaxy behaved as expected. Part of this signal was later assigned to a fresh new emission component, spatially correlated with the Galactic dust emission, which showed greater importance in the microwave range of frequencies. It has been named since as “anomalous microwave emission”, or AME. The current main hypothesis to explain the AME origin is that it is emitted by small dust particles which undergo fast spinning movements. In Fernández-Torreiro et al. (2023), we study the observational properties ofAdvertised on