New Worlds, New Horizons A Midterm Assessment (2016) / Chapter Skim
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1 Scientific Discoveries and Technical Advances
1 Scientific Discoveries and Technical Advances
Pages 13-28
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From page 13... ...
COSMIC DAWN: SEARCHING FOR THE FIRST STARS, GALAXIES, AND BLACK HOLES On the theme of cosmic dawn, the most important advances in the first half of the decade have come from large surveys of the high-redshift universe with the Hubble Space Telescope (HST) , often exploiting the near-infrared and grism capabilities of the Wide Field Camera 3 (WFC3)
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From page 14... ...
. Star forming galaxies grow steadily in number from z = 10 to z = 6, roughly tracking FIGURE 1.1 The Hubble Frontier Fields image of the galaxy cluster MACS J07175+3745.
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From page 15... ...
Specially designed radio experiments are now approaching the sensitivity thought needed to detect the predicted signals, and they have demonstrated the ability to remove contamination from astrophysical and terrestrial foregrounds, which present the most challenging technical obstacle to mapping reionization. Cosmological simulations and semi-analytic models, incorporating gravitational clustering, hydrodynamics, star formation, and radiative transfer, play a crucial role in connecting observed galaxy counts to the physical mechanisms of reionization and in making predictions for the complex structures expected in 21 cm maps.
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From page 16... ...
Transit measurements of planet diameters, especially when combined with mass measurements from radial velocity follow-up or from transit timing variations, provide critical diagnostics of exoplanet compositions. K epler discoveries range from dense, iron-rich planets like Mercury to planets of solid rock or molten lava, to water worlds and ice giants and gas iants puffier than g Jupiter and Saturn.
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From page 17... ...
Radial velocity instruments are now targeting the 0.1 m/s sensitivity needed to detect the reflex motion induced by Earth-like planets around Sun-like stars, a challenge that requires understanding and mitigating astrophysical sources of Doppler noise. JWST will provide a huge leap in sensitivity for transit spectroscopy of relatively cool planets, including many targets identified by TESS, allowing radically new insights into the composition and structure of exoplanet atmospheres.
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From page 18... ...
Coronagraphic instruments on 20- to 30-meter telescopes will sharpen the sensitivity and angular resolution of direct imaging searches and spectroscopic characterization of gas giants, while the WFIRST coronagraph is expected to push spectroscopy to the regime of Neptunes and super-Earths, and to demonstrate the technology that would eventually allow images and spectra of habitable worlds around nearby stars.
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From page 19... ...
, and, especially, the Planck satellite have confirmed ΛCDM predictions in exquisite detail, including the long series of acoustic oscillation peaks imprinted by primordial sound waves, the polarization power spectrum expected for adiabatic initial conditions that arise from quantum fluctuations during inflation, and a 40 σ standard deviation detection of the lensing of CMB fluctuations by clustered foreground dark matter (Figure 1.3)
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From page 20... ...
less in Wave Observatory the Plik and detectors from a merger of two 30 solar mass black holes at a distance (LIGO) As summarized in column 8 of Table 1, processing, beams, sky coverage, etc.
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From page 21... ...
This discovery confirmed some of the most exotic predictions of Einstein's theory of general relativity, and it demonstrated that 30 solar mass black holes exist and form close binary systems, that black hole mergers produce gravitational wave bursts that match the predictions of numerical relativity simulations and analytic calculations of the merged remnant's ringdown, and that the interferometric methods pioneered by LIGO are up to the challenge of detecting astrophysical sources of gravitational waves. Most importantly for the future, this discovery strongly suggests that sources within LIGO's sensitivity range are fairly common and that gravitational wave observations will rapidly open a new window on some of the most energetic phenomena in the cosmos.
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From page 22... ...
The Wide-Field Infrared Survey Explorer has revealed a large population of "Y dwarfs," objects with masses below the hydrogen-burning main sequence and surface temperatures below about 500 K One such Y dwarf has an effective temperature of only 250 K, cooler than Earth; recently, two brown dwarfs in a binary have been found only 2 parsecs away, mak ing these brown dwarfs some of the closest "stars" to the Sun.
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From page 23... ...
event horizon, and they are already constraining the black hole spin and the physical structure of its accretion flow. In addition to mapping the z > 6 galaxies of cosmic dawn, surveys from HST, Spitzer, Herschel Space Observatory, Chandra, ALMA, and ground-based optical telescopes have provided a much more detailed account of galaxy evolution through the epoch when the majority of stars in the universe formed.
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From page 24... ...
In the local universe, surveys using integral field spectrographs are providing detailed and unified maps of the stellar populations, chemical enrichment, gravita tional dynamics, and gas flows in large samples of nearby galaxies spanning a wide range of properties. These observations provide direct insights into the ecology of galaxies, the physics of star formation, and the origin of galactic winds, and they provide a new testing ground for cosmological simulations of galaxy formation.
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From page 25... ...
Kepler data have stimulated a burst of theoretical work on asteroseismology of red giants, which enables the Kepler measurements to probe the internal structure, rotation, and magnetic fields of evolved stars. The extraordinary diversity of Kepler planetary systems has stimulated theoretical investigations of the dynamical stability of tightly packed orbital configurations, the mechanisms that regulate orbital radii and eccentricity, and the physics that governs habitability.
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From page 26... ...
High-speed (100 ns) silicon drift detectors have been developed for the NICER (Neutron Star Interior Composition Explorer)
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From page 27... ...
At radio wavelengths, advances in digital signal processing technology combined with reductions in cost are making possible arrays composed of a large number of relatively small antenna elements, giving large fields of view with large collecting areas. These arrays enable comprehensive sky surveys with implications for cosmol 2 NASA, 2015, Wide-Field InfraRed Survey Telescope-Astrophysics Focused Telescope Assets WFIRST AFTA 2015 Report, Science Definition Team and WFIRST Study Office, https://arxiv.org/ftp/arxiv/ papers/1503/1503.03757.pdf.
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From page 28... ...
In the remainder of this decade, with the exception of LSST, the Department of Energy-funded dark energy program build ing the DESI spectrograph, and some smaller-scale programs funded by the Major Research Instrumentation Program, ground-based optical and infrared instrumen tation will likely slow significantly.
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