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2 A New Cosmic Perspective
Pages 31-80

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From page 31...
... The investments of previous decades bore fruit in this decade in the awarding of Nobel Prizes in Physics for six discoveries derived from astronomical measurements: dark energy, neutrino oscillations, gravitational waves, exoplanets, physical cosmology, and black holes (Figure 2.1)
From page 32...
... In 2011, Saul Perlmutter, Adam Riess, and Brian Schmidt received the prize "for the discovery of the accelerating expansion of the universe through observations of distant supernovae." The citation to Takaaki Kajita and Arthur McDonald in 2015 was "for the discovery of neutrino oscillations, which shows that neutrinos have mass." In 2017, Kip Thorne, Rainer Weiss and Barry Barish were awarded the prize "for decisive contributions to the LIGO detector and the observations of gravitational waves." The year 2019 saw the awarding of the Nobel Prize in Physics to James Peebles "for theoretical discoveries in physical cosmology" and to Dider Queloz and Michael Mayor "for the discovery of an exoplanet orbiting a solar-type star." Most recently, in 2020, the topic of black holes received Nobel attention, with recognition to Roger Penrose "for the discovery that black hole formation is a robust theory of general relativity" and to Andrea Ghez and Reinhard Genzel "for the discovery of a supermassive compact object at the center of our galaxy." SOURCE: 2011: NASA/STScI/Ann Field; 2015: Kamioka Observatory, ICRR (Institute for Cosmic Ray Research) , The University of Tokyo; 2017: R
From page 33...
... It soon became clear that most of the science questions and discovery areas could be organized into three broad thematic areas: Worlds and Suns in Context highlights the extraordinary advances over the past decade in the study of exoplanets, stars, and their associated planetary systems, and the opportunities for transformational advances in these areas, including the ultimate search and characterization of habitable planets, in the decades ahead. Cosmic Ecosystems represents an integration and culmination of understanding the origins of galaxies, stars, planets, and massive black holes, and the realization that the life cycles of the universe over this billionfold range of scales are intimately connected, through feedback processes propagating through the gas within, surrounding, and between galaxies.
From page 35...
... In the coming decades, high-resolution spectroscopy with extremely large telescopes will expand these abundance measurements PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 2-5
From page 37...
... The interplay between magnetic flux and mass flows is of universal PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 2-7
From page 38...
... Optical and infrared interferometric observations have begun to localize these regions. Observations spanning multiple regions of the electromagnetic spectrum provide independent constraints on the properties of these features, PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 2-8
From page 40...
... A method prioritized by New Worlds, New Horizons, gravitational microlensing, will be used by the Roman Space Telescope in this decade to complete the planetary census by finding planets from 1 to 100 AU, and even free-floating planets. Microlensing exploits the bending of light by the gravity of the PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 2-10
From page 43...
... These telescopes will revolutionize the understanding of the composition of exoplanets. Atmospheres are the PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 2-13
From page 46...
... Measurements of the composition, orbital dynamics, and size distributions of small bodies in the solar system provide crucial benchmarks for understanding solar system formation in one spectacularly detailed instance. Time-domain surveys such as the Vera Rubin Observatory's Legacy PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 2-16
From page 49...
... make it easier to detect an PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 2-19
From page 51...
... Radio observations revealed the existence of neutron stars, whose remarkably stable rotation rates have since been used to discover planets and confirm the theory of general relativity's prediction of orbital decay via the emission of gravitational waves. And telescopes observing in the infrared can peer into the enshrouded stellar nurseries where stars and planets form.
From page 52...
... Starting in 2015, LIGO opened up the gravitational wave view of the universe by detecting merging binary black holes. The simultaneous detection of gravitational waves and electromagnetic radiation from a binary neutron star merger in 2017 showed the power and complementarity of multi-messenger observations (see Box 2.2)
From page 54...
... This is due to multiple breakthrough discoveries in the last decade, PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 2-24
From page 55...
... These seemingly separate advances in observational techniques are in fact intimately related: most of the known and anticipated sources of gravitational waves, neutrinos, and cosmic rays are also time variable or transient electromagnetic sources (e.g., neutron star mergers, gamma-ray bursts, black hole jets, and stellar explosions)
From page 57...
... . Although the single measurement with GW170817 is not as precise as other techniques, multi-messenger cosmology will increase in importance in the coming decade as we detect ever more binary neutron star and black hole mergers.
From page 59...
... . The importance of gravitational waves lies in part with the central role that black holes and neutron stars play in many areas of astronomy, from stellar evolution to galaxy formation.
From page 60...
... The population of neutron star and black hole mergers with masses of ~2-5 Msun in the ‘mass gap' between neutron stars and black holes will provide key constraints on our understanding of massive stellar evolution, the maximum mass of neutron stars, and core-collapse explosion physics. Combined gravitational wave and electromagnetic observations have the potential to finally crack the longstanding puzzle of the origin and growth of massive black holes, one that lies at the intersection of the understanding of stars, galaxies, accretion disks, and cosmology.
From page 61...
... Over the few years since then, gravitational wave observations have become an indispensable astronomical tool. The coming decade, with the potential of detections in other parts of the gravitational wave spectrum, signals from new sources, and large numbers of black hole and neutron star detections, will be the start of a new era of precision and multi-wavelength gravitational wave astronomy.
From page 63...
... Within this discovery landscape, driven by improvements in gravitational wave and neutrino detection, and upcoming facilities such as the Rubin Observatory, one priority area stands out: the application of these new tools to the formation, evolution, and nature of compact stellar remnants such as white dwarfs, neutron stars, and black holes, as probed by the gravitational wave signatures of their mergers, together with rare explosive events that can be explored by the unique cadence and multi-color sensitivity of the Rubin Observatory. Sensitive observations of high-energy neutrinos and charged particles add new elements of discovery space, which will probe the universe's most extreme particle accelerators -- New Windows on the Dynamic Universe.
From page 64...
... Likewise, the flow of matter and energy within a galaxy -- again PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 2-34
From page 65...
... In this way, the first stars and black holes were able to cause a global phase transition over scales of hundreds of Megaparsecs, in which most of the hydrogen in the universe was converted from a neutral to an ionized state, during what is referred to as the "Epoch of Reionization". Identifying the sources of cosmic reionization, and PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 2-35
From page 66...
... This leads to large uncertainties in which massive stars become neutron stars and which become black holes. Stellar winds are also believed to play an important role in dispersing star-forming molecular clouds and driving turbulence in the interstellar medium, but the efficiency of this feedback again depends on the uncertain strength of winds from massive stars.
From page 67...
... Supernovae are important for a second, less direct, reason, in that they produce the gigaelectronvolt (GeV) cosmic rays PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 2-37
From page 68...
... More detailed studies of molecular gas emission will reveal how the PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 2-38
From page 69...
... In addition to measuring the jet and wind properties, better constraints on the masses and spins of the supermassive black holes themselves will play in important role in understanding how these objects formed and how they grow, as well as their role in the feedback processes described above. X-ray telescopes and next generation gravitational wave experiments can constrain the black hole spins, and their masses will be better constrained by measurements with next generation optical and radio telescopes.
From page 71...
... Or does an entirely different set of processes seed galactic nuclei with massive black holes at high redshift? A combination of gravitational wave measurements of black hole mergers across cosmic time (see Section 2.2)
From page 72...
... Theoretically, it is likely that small-scale physical processes such as instabilities and thermal PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 2-42
From page 75...
... An essential milestone on the pathway to revealing these drivers is a complete understanding of the formation and buildup of galaxies and their structures, stellar populations, metals, and central black PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 2-45
From page 76...
... Over the coming decade, major contributions to these investigations will come from multi-wavelength observations with the JVLA, ALMA, VRO, Euclid, Roman, 3.5-10 m OIR telescopes, Chandra, and toward the end of this period by the ESA Athena mission. Athena's emphasis on The Hot and Energetic Universe will provide especially unique and powerful constraints on the cosmic feedback cycle, especially from AGNs, and it underscores the critical importance of future X-ray and infrared missions if these scientific questions are PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 2-46
From page 77...
... Many objects in the universe change their intensity with time, in a way that illuminates the astrophysics of the object itself or makes it amenable to study some other phenomenon: witness the monitoring of quasar spectra over time to illuminate the innermost regions near the center of a galaxy around the central supermassive black hole, as well as studies of the lifetime and distribution of starspots through long-term precision light curves. The time domain also encompasses eruptions and explosions, from nova outbursts of episodic accretion to the merging of two neutron stars, which produce both electromagnetic and gravitational wave signals during the final coalescence, to the high energy flares that may prevent the development of life on otherwise Earth-like planets orbiting magnetically active stars.
From page 78...
... General relativistic simulations of black hole accretion advance state-of-the-art predictions of the behavior of jets and winds from these compact objects, which can be compared with observations. From theory and simulations, a more complete knowledge of stars, as far as their rotation, binarity, and the impact of magnetic fields, improves the ability to model and interpret the expected ionizing output from massive stars.
From page 79...
... Worlds and Suns in Context How do the Sun and other stars create space weather? Worlds and Suns in Context PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 2-49
From page 80...
... TABLE 2.2 Science Panel Discovery Areas Discovery Area Theme(s) Panel on Compact Objects and Energetic Phenomena: New Messengers and New Physics Transforming our View of the Universe by Combining New Information from Light, Particles, and Gravitational Waves Panel on Cosmology: New Messengers and New Physics The Dark Ages as a Cosmological Probe Panel on Galaxies: Cosmic Ecosystem Mapping the Circumgalactic Medium and Intergalactic Medium in Emission Panel on Exoplanets, Astrobiology, and the Solar System: Worlds and Suns in Context The Search for Life on Exoplanets Panel on the Interstellar Medium and Star and Planet Formation: Worlds and Suns in Context Detecting and Characterizing Forming Planets Panel on Stars, the Sun, and Stellar Populations: Worlds and Suns in Context, Cosmic Ecosystem "Industrial Scale" Spectroscopy PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION 2-50


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