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Appendix G: Report of the Panel on Stars, the Sun, and Stellar Populations
Pages 325-341

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From page 325...
... The scope of the Panel on Stars, the Sun, and Stellar Populations includes stellar structure and evolution, stellar activity and variability, brown dwarfs, ground-based solar astrophysics, resolved stellar populations including star clusters, nucleosynthesis and chemical evolution. In the course of its work, the panel reviewed and incorporated the input of over 150 white papers submitted by the astronomy and astrophysics community addressing the preceding topics, as well as broader areas of astronomy in which stars are tools for studying fundamental physics, exploring the interstellar and intergalactic media, and probing distant galaxies.
From page 326...
... We start with the Sun. The goal of modern solar physics research is to understand the entire Sun, from the core to the heliopause, in order to provide a holistic description of variations in its magnetic fields and the associated eruptive phenomena that can affect life on Earth.
From page 327...
... Extreme or episodic changes in loss rates can significantly hasten the evolutionary time scale to a star's end phases. We have also learned that about 10 percent of massive stars possess strong surface magnetic fields (~0.3–20 kG)
From page 328...
... These include questions about the fundamental mechanisms driving magnetic field generation and its influence on internal structure, surface heterogeneity, wind generation, and environmental influence across the mass spectrum; the temporally and spatially dynamic properties of stars, and their internal to external manifestations; and the formation and co-evolution of stellar multiples, and their influence on the end states of massive stars. Moreover, with new technologies, computational tools and theoretical developments, we have the opportunity to build a complex and comprehensive assessment of stellar populations throughout the Milky Way and beyond.
From page 329...
... Incomplete stellar samples limit our knowledge of the initial mass function, and may miss rapid evolutionary stages that dominate a stellar PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION G-5
From page 330...
... Those in very widely separated systems are crucial probes of star formation processes and coeval laboratories for stellar structure and evolution studies, and constrain the properties of the Milky Way's dark matter. Those in very closely separated systems have fates that are PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION G-6
From page 331...
... Among other parameters, we need to know the orbital properties and mass ratios of multiple-star systems across age, mass, mass-loss rates, and composition. While we know that multiplicity is more common in high-mass than in low-mass stars, we have incomplete information on the statistics of systems with extreme mass ratios, long orbit periods, and very low masses (e.g., brown dwarfs)
From page 333...
... This is one of the main issues in understanding the evolution of massive red supergiants like Betelgeuse. Understanding the evolution of various astrophysical phenomena, from exoplanet atmospheres to solar-like magnetospheres to the interaction of core-collapse SNe with circumstellar medium requires an PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION G-9
From page 334...
... The radiation-driven winds of massive stars interact with the circumstellar environment, creating nebulae filled with gas and dust. A massive star's evolution depends on its mass loss rate, which in turn depends on metallicity as the wind acts on the highly ionized metals produced by the star, and on magnetic field strength, now measured in 10 percent of hot stars.
From page 335...
... While Athena's microcalorimeter will provide high-resolution spectra for the most energetic phenomena such as stellar flares, studies of quiescent and/or lower energy phenomena, such as coronal PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION G-11
From page 336...
... The construction of the 4 m DKIST is almost complete PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION G-12
From page 337...
... Panchromatic spectroscopy, facilitated by advanced UV and X-ray facilities, probes the full range of stellar phenomena, including coronal heating and mass ejection processes in the X ray, mass loss from massive stars and atomic abundances of metal-poor stars in the UV, and the molecular chemistry of very cool and highly embedded stars in the infrared. Multiepoch observations map stellar binaries and reveal invisible companions, probe stellar interiors through precision asteroseismic measurements, and unveil the dynamic atmospheres of cloudy brown dwarfs and massive evolving stars.
From page 338...
... The next decade of astronomical research will rely on advanced software tools to analyze and interpret massive observational and theoretical data sets. The Image Reduction and Analysis Facility (IRAF)
From page 339...
... Evolution of solar magnetic Broadband (< 1 to > 20 GHz) spatially resolved observations of the Sun structures and related internal changes measurements, frequency resolution better than 5 percent, time resolution of ~10 s.
From page 340...
... Abundance of the most High-resolution spectrometer and spectropolarimetry metal-poor stars spectropolarimeter covering wide wavelength (G-Q3) Stellar surface feature mapping domains to cover lines formed from 104 to 107 (G-Q3)


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