About this Research Topic
Planetary nebulae (PNe) are constituted by ionized gas around an evolved low-intermediate mass star. The nebula was part of the stellar atmosphere ejected during the AGB stellar phase. The star is a post-AGB object which has evolved crossing the HR diagram and has an effective temperature of 28,000 K or more. It emits a large fraction of UV photons that ionize the envelope. PNe are mainly studied through imaging, photometry and low- and high-resolution spectroscopy techniques which allow to determine the physical conditions and chemical abundances of the elements present in the plasma. Through this analysis it is possible to study the physical processes in ionized plasmas (the physical conditions of density and temperature and the nebular chemistry can be determined), the evolution and characteristics of the central star, the mechanisms of ejection of the nebula and the evolution of the interstellar medium (ISM) which will be enriched with elements produced in the stellar nucleosynthesis and brought to the stellar surface via several dredge-up episodes. Besides the analysis of stellar and galactic evolution, PNe are used to study the kinematics of galaxies and their distances through the [OIII]5007 Planetary Nebula Luminosity Function which is a standard secondary candle up to 20 Mpc.
The Sun probably will evolve into a PN at the end of its life as a star, therefore the analysis of planetary nebulae and their conditions helps to understand the future of our star and its effects on the solar system.
The main aim of this Research topic is to analyze the PNe characteristics in order to infer the recent advances relative to 1) the mechanisms of formation and evolution of the nebular shells that can be studied by analysis of kinematics of shells and hydrodynamical modelling, 2) the stellar nucleosynthesis that contaminates the star atmosphere with newly formed elements (mainly He, C and N), subsequently ejected to the ISM with the PN, 3) the abundance discrepancy factors in PNe where abundances determined through collitionally excited lines are much lower than those determined through recombination lines, 4) the contribution of PNe as distance standard candles for external galaxies, through the PNLF, 5) the chemical gradients in disk galaxies and their evolution with time, 6) the nebular evolution and its impact in the ISM, 7) the nebular evolution with time relative to the stellar evolution, 8) the relation between present and initial stellar masses, 9) the future of the Sun and the solar system when the PN state has been acquired, and many others.
The PNe subject is a very active field in the present astrophysics and each year advances are achieved by specialists which are reported in scientific papers and in regular congresses and symposia on the subject. This Research Topic welcomes a range of article-types, on themes including:
• The chemistry in PNe, do we understand it well? (The Abundance Discrepancy Factor in PNe).
• Studies of variable PNe. What can be infer about their central star variability?
• Following PNe central stars in the HR diagram: their initial-final mass relation.
• The chemical evolution of the ISM medium, how low-intermediate mass stars contribute?
• PNe as standard candles in nearby galaxies.
The Sun probably will evolve into a PN at the end of its life as a star, therefore the analysis of planetary nebulae and their conditions helps to understand the future of our star and its effects on the solar system.
The main aim of this Research topic is to analyze the PNe characteristics in order to infer the recent advances relative to 1) the mechanisms of formation and evolution of the nebular shells that can be studied by analysis of kinematics of shells and hydrodynamical modelling, 2) the stellar nucleosynthesis that contaminates the star atmosphere with newly formed elements (mainly He, C and N), subsequently ejected to the ISM with the PN, 3) the abundance discrepancy factors in PNe where abundances determined through collitionally excited lines are much lower than those determined through recombination lines, 4) the contribution of PNe as distance standard candles for external galaxies, through the PNLF, 5) the chemical gradients in disk galaxies and their evolution with time, 6) the nebular evolution and its impact in the ISM, 7) the nebular evolution with time relative to the stellar evolution, 8) the relation between present and initial stellar masses, 9) the future of the Sun and the solar system when the PN state has been acquired, and many others.
The PNe subject is a very active field in the present astrophysics and each year advances are achieved by specialists which are reported in scientific papers and in regular congresses and symposia on the subject. This Research Topic welcomes a range of article-types, on themes including:
• The chemistry in PNe, do we understand it well? (The Abundance Discrepancy Factor in PNe).
• Studies of variable PNe. What can be infer about their central star variability?
• Following PNe central stars in the HR diagram: their initial-final mass relation.
• The chemical evolution of the ISM medium, how low-intermediate mass stars contribute?
• PNe as standard candles in nearby galaxies.
Keywords: Chemical Abundances, Shaping of Stellar Winds, Hydrodynamics, Stellar Evolution, Binary Interactions
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