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From page 284... ... to characterize star formation histories at the earliest epochs out to ~3 Mpc. Large fields, like those covered by the Rubin Observatory and Roman, will enable efficient observations of typical Milky Way dwarfs, with high target density for simultaneous observation of nearby stars. Read the entire page →
From page 285... ... An important benchmark for testing the paradigm established over the past decade in which bursty star formation gravitationally heats the central regions of the host dark matter halos is to reach Mstars <<109 M⊙ systems, where this feedback-induced effect is predicted to be most efficient. Deep ALMA observations of the restframe far-IR [CII] Read the entire page →
From page 286... ... a full baryon and metal accounting in different gas phases at different redshifts, (2) how galaxies acquire fuel for sustaining star formation, and (3) Read the entire page →
From page 287... ... The combination of X-ray and SZ maps is a much stronger diagnostic of density and temperature structure than either observable on its own. Next-decade facilities will push the limits to a few times higher angular resolution and higher sensitivity than the Planck satellite, with SZ Read the entire page →
From page 288... ... A summary table (Table D.1) showing the flow from the science questions, sub-topics, and the discovery area to the observational and theoretical needs as presented in this report is given below. Read the entire page →
From page 289... ... host galaxies? of intermediate-mass black holes. Read the entire page →
From page 290... ... The dynamical and chemical history of • All-sky optical/NIR multi-object galaxies and their dark matter halos the Milky Way. spectroscopy for abundances and shape their observable properties? Read the entire page →
From page 291... ... E Report of the Panel on Exoplanets, Astrobiology, and the Solar System OVERVIEW In the past decade, the field of exoplanet science has rapidly expanded with the discoveries of thousands of new planets and the characterization of worlds unlike those in our solar system. From the ensuing treasure trove of exoplanet demographics and characteristics, we have learned that most, if not all, stars host planets and that planets smaller than Neptune are ubiquitous. Read the entire page →
From page 292... ... In the near term, the James Webb Space Telescope (JWST) and ground-based telescopes will have the sensitivity to search for and begin to characterize the atmospheres of a handful of terrestrial planets orbiting the closest M dwarf stars. Read the entire page →
From page 293... ... Charbonneau, 2015, "The Occurrence of Potentially Habitable Planets Orbiting M Dwarfs Estimated from the Full Kepler Dataset and an Empirical Measurement of the Detection Sensitivity," Astrophysical Journal 807:45. Read the entire page →
From page 294... ... High-resolution spectroscopy has measured precise thermal profiles, winds, and rotation rates for a handful of giant planets. The Hubble Space Telescope (HST) Read the entire page →
From page 295... ... Transmission spectroscopy can never be sensitive to the planetary surface, supporting the need for future direct spectroscopy of potentially habitable worlds. Last, atmospheric characterization has focused almost exclusively on shorter period, larger planets, and we cannot yet systematically connect atmospheric composition to the density/bulk compositional properties of longer period planets of all sizes, which often have less well characterized masses and radii. Read the entire page →
From page 296... ... 6 In addition to community inputs in the form of white papers and presentations, the congressionally mandated reports by the National Academies of Sciences, Engineering, and Medicine, Exoplanet Science Strategy and An Astrobiology Strategy for the Search for Life in the Universe, were considered as inputs to the panel. Read the entire page →
From page 297... ... The Nancy Grace Roman Space Telescope microlensing survey is poised to greatly expand our knowledge to longer orbital periods and lower planet masses across a wide range of stellar spectral types, filling key gaps in the census and providing a statistical anchor for planet formation and evolution models. Much like the Kepler data set revealed a gap in planet radii indicative of atmospheric evaporation, these extended demographics should give insight into physical processes governing planetary systems -- for example, by detecting an enhanced density of planets near the snowlines of systems. Read the entire page →
From page 298... ... . Smaller dust grains produced by planetesimals are observable with facilities like the HST Space Telescope Imaging Spectrograph (STIS) Read the entire page →
From page 299... ... However, to complete the census of nearby systems, detection of nontransiting potentially habitable planets around Sun-like stars will require improved RV sensitivity and space-based direct imaging. Solar observations and collaboration with heliophysicists may be fruitful for understanding and modeling the effects of stellar variability on RV observations (compare to Section G-Q3 in Appendix G) Read the entire page →
From page 300... ... For terrestrial planets, surface/atmosphere exchange mechanisms mediate atmospheric composition, and planetary magnetic fields can illuminate processes occurring deep in a planet's interior, while providing critical insights into how the planet's atmosphere interacts with the space environment. Meeting the goal of determining the bulk composition of a planet thus entails connecting the observable atmosphere, as sculpted by such processes, to deep atmospheric or surface processes and chemical composition. Read the entire page →
From page 301... ... Characterizing the differences and similarities of the two classes of objects will elucidate their formation mechanisms, informing the limits of both planet and star formation (compare to Section G-Q1 in Appendix G) Read the entire page →
From page 302... ... Answering this question requires an improved history of volatiles in our solar system, characterization of volatiles in exoplanet systems, and modeling how volatiles are acquired and lost by potentially habitable planets. Completing the volatile and organic inventory of planets within the solar system, including the dwarf planets, asteroids, KBOs, and comets, and determining the dynamical interactions that formed these populations, provides the tightest constraints on the properties of the protoplanetary disk from which our system formed. Read the entire page →
From page 303... ... E-Q3c. What Is the Range of Potentially Habitable Environments Around Different Types of Stars? Read the entire page →
From page 304... ... 304 PATHWAYS TO DISCOVERY IN ASTRONOMY AND ASTROPHYSICS FOR THE 2020s constraining the surface conditions. Strongly interdisciplinary efforts, combining observations, laboratory, and theoretical studies, are needed to study and identify signs of habitability prior to future observations. Read the entire page →

From page 284...

... to characterize star formation histories at the earliest epochs out to ~3 Mpc. Large fields, like those covered by the Rubin Observatory and Roman, will enable efficient observations of typical Milky Way dwarfs, with high target density for simultaneous observation of nearby stars.