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Victoria S Meadows, Giada N Arney, Edward W Schwieterman, Jacob Lustig-Yaeger, Andrew P Lincowski, Tyler Robinson, Shawn D Domagal-Goldman, Russell Deitrick, Rory K Barnes, David P Fleming, Rodrigo Luger, Peter E Driscoll, Thomas R Quinn, David Crisp
Proxima Centauri b provides an unprecedented opportunity to understand the evolution and nature of terrestrial planets orbiting M dwarfs. Although Proxima Cen b orbits within its star's habitable zone, multiple plausible evolutionary paths could have generated different environments that may or may not be habitable. Here, we use 1-D coupled climate-photochemical models to generate self-consistent atmospheres for several evolutionary scenarios, including high-O2, high-CO2, and more Earth-like atmospheres, with both oxic and anoxic compositions...
February 12, 2018: Astrobiology
Anthony Harness, Stuart Shaklan, Webster Cash, Philip Dumont
Starshade external occulters are a leading technology that provide the starlight suppression needed to directly image and spectroscopically characterize Earth-sized exoplanets in the habitable zone of nearby stars. A high-priority technology area identified in need of development for a future starshade mission is the development and validation of high-fidelity optical models to predict the performance of a full-scale starshade. We present the generalization of an algorithm to formulate the Fresnel diffraction equation as a one-dimensional integral around the edge of an arbitrary binary diffraction screen...
February 1, 2018: Journal of the Optical Society of America. A, Optics, Image Science, and Vision
Joshua Krissansen-Totton, Stephanie Olson, David C Catling
Chemical disequilibrium in planetary atmospheres has been proposed as a generalized method for detecting life on exoplanets through remote spectroscopy. Among solar system planets with substantial atmospheres, the modern Earth has the largest thermodynamic chemical disequilibrium due to the presence of life. However, how this disequilibrium changed over time and, in particular, the biogenic disequilibria maintained in the anoxic Archean or less oxic Proterozoic eons are unknown. We calculate the atmosphere-ocean disequilibrium in the Precambrian using conservative proxy- and model-based estimates of early atmospheric and oceanic compositions...
January 2018: Science Advances
Joseph R Schmitt, Jon M Jenkins, Debra A Fischer
The vast majority of the 4700 confirmed planets and planet candidates discovered by the Kepler space telescope were first found by the Kepler pipeline. In the pipeline, after a transit signal is found, all data points associated with those transits are removed, creating a "Swiss cheese"-like light curve full of holes, which is then used for subsequent transit searches. These holes could render an additional planet undetectable (or "lost"). We examine a sample of 114 stars with 3+ confirmed planets to see the effect that this "Swiss cheesing" may have...
April 2017: Astronomical Journal
Engin Keles, John Lee Grenfell, Mareike Godolt, Barbara Stracke, Heike Rauer
Understanding the possible climatic conditions on rocky extrasolar planets, and thereby their potential habitability, is one of the major subjects of exoplanet research. Determining how the climate, as well as potential atmospheric biosignatures, changes under different conditions is a key aspect when studying Earth-like exoplanets. One important property is the atmospheric mass, hence pressure and its influence on the climatic conditions. Therefore, the aim of the present study is to understand the influence of atmospheric mass on climate, hence habitability, and the spectral appearance of planets with Earth-like, that is, N2-O2 dominated, atmospheres orbiting the Sun at 1 AU...
January 24, 2018: Astrobiology
Daniel Clery
No abstract text is available yet for this article.
January 19, 2018: Science
Javier Tiffenberg, Miguel Sofo-Haro, Alex Drlica-Wagner, Rouven Essig, Yann Guardincerri, Steve Holland, Tomer Volansky, Tien-Tien Yu
We have developed ultralow-noise electronics in combination with repetitive, nondestructive readout of a thick, fully depleted charge-coupled device (CCD) to achieve an unprecedented noise level of 0.068  e^{-} rms/pixel. This is the first time that discrete subelectron readout noise has been achieved reproducible over millions of pixels on a stable, large-area detector. This enables the contemporaneous, discrete, and quantized measurement of charge in pixels, irrespective of whether they contain zero electrons or thousands of electrons...
September 29, 2017: Physical Review Letters
Caleb Scharf, Debra Fischer, Victoria Meadows
No abstract text is available yet for this article.
January 11, 2018: Nature
Chuanfei Dong, Meng Jin, Manasvi Lingam, Vladimir S Airapetian, Yingjuan Ma, Bart van der Holst
The presence of an atmosphere over sufficiently long timescales is widely perceived as one of the most prominent criteria associated with planetary surface habitability. We address the crucial question of whether the seven Earth-sized planets transiting the recently discovered ultracool dwarf star TRAPPIST-1 are capable of retaining their atmospheres. To this effect, we carry out numerical simulations to characterize the stellar wind of TRAPPIST-1 and the atmospheric ion escape rates for all of the seven planets...
December 28, 2017: Proceedings of the National Academy of Sciences of the United States of America
Vincent Bourrier, Christophe Lovis, Hervé Beust, David Ehrenreich, Gregory W Henry, Nicola Astudillo-Defru, Romain Allart, Xavier Bonfils, Damien Ségransan, Xavier Delfosse, Heather M Cegla, Aurélien Wyttenbach, Kevin Heng, Baptiste Lavie, Francesco Pepe
The angle between the spin of a star and the orbital planes of its planets traces the history of the planetary system. Exoplanets orbiting close to cool stars are expected to be on circular, aligned orbits because of strong tidal interactions with the stellar convective envelope. Spin-orbit alignment can be measured when the planet transits its star, but such ground-based spectroscopic measurements are challenging for cool, slowly rotating stars. Here we report the three-dimensional characterization of the trajectory of an exoplanet around an M dwarf star, derived by mapping the spectrum of the stellar photosphere along the chord transited by the planet...
December 18, 2017: Nature
Thomas P Greene, Douglas M Kelly, John Stansberry, Jarron Leisenring, Eiichi Egami, Everett Schlawin, Laurie Chu, Klaus W Hodapp, Marcia Rieke
The James Webb Space Telescope near-infrared camera (JWST NIRCam) has two 2'. 2 × 2'.2 fields of view that can be observed with either imaging or spectroscopic modes. Either of two R ∼ 1500 grisms with orthogonal dispersion directions can be used for slitless spectroscopy over λ = 2.4 - 5.0 μm in each module, and shorter wavelength observations of the same fields can be obtained simultaneously. We describe the design drivers and parameters of the grisms and present the latest predicted spectroscopic sensitivities, saturation limits, resolving powers, and wavelength coverage values...
July 2017: Journal of Astronomical Telescopes, Instruments, and Systems
Giada Arney, Shawn D Domagal-Goldman, Victoria S Meadows
Early Earth may have hosted a biologically mediated global organic haze during the Archean eon (3.8-2.5 billion years ago). This haze would have significantly impacted multiple aspects of our planet, including its potential for habitability and its spectral appearance. Here, we model worlds with Archean-like levels of carbon dioxide orbiting the ancient Sun and an M4V dwarf (GJ 876) and show that organic haze formation requires methane fluxes consistent with estimated Earth-like biological production rates...
November 30, 2017: Astrobiology
Alexandra Witze
No abstract text is available yet for this article.
November 20, 2017: Nature
(no author information available yet)
No abstract text is available yet for this article.
November 23, 2017: Nature
Duo Cui, Feng Tian, Yuwei Wang, Changshen Li, Chaoqing Yu, Le Yu
One signature of life on Earth is the vegetation red edge (VRE) feature of land plants, a dramatic change of reflectivity at wavelength near 0.7 μm. Potentially habitable planets around M dwarfs are tidally locked, which can limit the distribution of land plants. In this study, we used a biogeochemical model to investigate the distribution of land plants on potentially habitable planets around M dwarfs driven by climate data produced in a general circulation model (GCM). When considering the effects of clouds, the observation time needed for VRE detection on nearby p = 1 exoplanets around nearby M dwarfs is on the order of days using a 25 m2 telescope if a large continent faces Earth during observations...
December 2017: Astrobiology
Kieran Hand, Edwin Yates
Conditions on exoplanets include elevated temperatures and pressures. The response of carbon-based biological macromolecules to such conditions is then relevant to the viability of life. The capacity of proteins and ribozymes to catalyse reactions or bind receptors, and nucleic acids to convey information, depends on them sampling different conformational states. These are determined by macromolecular vibrational states, or phonon modes, accessible using terahertz (THz: 1012 Hz) absorption spectroscopy. THz spectra of biological macromolecules exhibit broad absorption at approximately 6 THz (equating to approx...
November 2017: Journal of the Royal Society, Interface
Vladimir S Airapetian, Charles H Jackman, Martin Mlynczak, William Danchi, Linda Hunt
The current explosion in detection and characterization of thousands of extrasolar planets from the Kepler mission, the Hubble Space Telescope, and large ground-based telescopes opens a new era in searches for Earth-analog exoplanets with conditions suitable for sustaining life. As more Earth-sized exoplanets are detected in the near future, we will soon have an opportunity to identify habitale worlds. Which atmospheric biosignature gases from habitable planets can be detected with our current capabilities? The detection of the common biosignatures from nitrogen-oxygen rich terrestrial-type exoplanets including molecular oxygen (O2), ozone (O3), water vapor (H2O), carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) requires days of integration time with largest space telescopes, and thus are very challenging for current instruments...
November 2, 2017: Scientific Reports
Jan Tepper, Lucas Labadie, Simon Gross, Alexander Arriola, Stefano Minardi, Romina Diener, Michael J Withford
Astronomical interferometry is a unique technique that allows observation with angular resolutions on the milliarcsec scale by combining the light of several apertures hundreds of meters apart. The PIONIER and GRAVITY instruments at the Very Large Telescope Interferometer have demonstrated that silica-based integrated optics (IO) provide a small-scale and highly stable solution for the interferometric beam combination process. Yet, important science cases such as exoplanet hunting or the spectroscopic characterization of exoplanetary atmospheres are favorable for observation in the mid-IR, namely the atmospheric windows L and L' band (3-4 µm), a wavelength range that is not covered by conventional silica-based IO...
August 21, 2017: Optics Express
P Szypryt, S R Meeker, G Coiffard, N Fruitwala, B Bumble, G Ulbricht, A B Walter, M Daal, C Bockstiegel, G Collura, N Zobrist, I Lipartito, B A Mazin
We have fabricated and characterized 10,000 and 20,440 pixel Microwave Kinetic Inductance Detector (MKID) arrays for the Dark-speckle Near-IR Energy-resolved Superconducting Spectrophotometer (DARKNESS) and the MKID Exoplanet Camera (MEC). These instruments are designed to sit behind adaptive optics systems with the goal of directly imaging exoplanets in a 800-1400 nm band. Previous large optical and near-IR MKID arrays were fabricated using substoichiometric titanium nitride (TiN) on a silicon substrate. These arrays, however, suffered from severe non-uniformities in the TiN critical temperature, causing resonances to shift away from their designed values and lowering usable detector yield...
October 16, 2017: Optics Express
Elyar Sedaghati, Henri M J Boffin, Ryan J MacDonald, Siddharth Gandhi, Nikku Madhusudhan, Neale P Gibson, Mahmoudreza Oshagh, Antonio Claret, Heike Rauer
As an exoplanet transits its host star, some of the light from the star is absorbed by the atoms and molecules in the planet's atmosphere, causing the planet to seem bigger; plotting the planet's observed size as a function of the wavelength of the light produces a transmission spectrum. Measuring the tiny variations in the transmission spectrum, together with atmospheric modelling, then gives clues to the properties of the exoplanet's atmosphere. Chemical species composed of light elements-such as hydrogen, oxygen, carbon, sodium and potassium-have in this way been detected in the atmospheres of several hot giant exoplanets, but molecules composed of heavier elements have thus far proved elusive...
September 13, 2017: Nature
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