scholarly journals High-resolution reflection spectra for Proxima b and Trappist-1e models for ELT observations

2019 ◽  
Author(s):  
Z Lin ◽  
L Kaltenegger
Keyword(s):  
High Resolution ◽  
Reflection Spectra ◽  
Habitable Zone ◽  
Climate Indicators ◽  
Reflected Light ◽  
Earth Like Planets ◽  
M Stars ◽  
Large Telescopes ◽  
Host Stars ◽  
Absorption Features

ABSTRACT The closest stars that harbor potentially habitable planets are cool M-stars. Upcoming ground- and space-based telescopes will be able to search the atmosphere of such planets for a range of chemicals. To facilitate this search and to inform upcoming observations, we model the high-resolution reflection spectra of two of the closest potentially habitable exoplanets for a range of terrestrial atmospheres and surface pressures for active and inactive phases of their host stars for both oxic and anoxic conditions: Proxima b, the closest potentially habitable exoplanet, and Trappist-1e, one of 3 Earth-size planets orbiting in the Habitable Zone of Trappist-1. We find that atmospheric spectral features, including biosignatures like O2 in combination with a reduced gas like CH4 for oxic atmospheres, as well as climate indicators like CO2 and H2O for all atmospheres, show absorption features in the spectra of Proxima b and Trappist-1e models. However for some features like oxygen, high-resolution observations will be critical to identify them in a planet's reflected flux. Thus these two planets will be among the best targets for upcoming observations of potential Earth-like planets in reflected light with planned Extremely Large Telescopes.

scholarly journals How surfaces shape the climate of habitable exoplanets

2020 ◽  
Vol 495 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Jack Madden ◽  
Lisa Kaltenegger
Keyword(s):  
Surface Albedo ◽  
Atmospheric Composition ◽  
Habitable Zone ◽  
Planetary Surfaces ◽  
Earth Like Planets ◽  
Planetary Environment ◽  
Near Future ◽  
Host Stars

ABSTRACT Large ground- and space-based telescopes will be able to observe Earth-like planets in the near future. We explore how different planetary surfaces can strongly influence the climate, atmospheric composition, and remotely detectable spectra of terrestrial rocky exoplanets in the habitable zone depending on the host star’s incident irradiation spectrum for a range of Sun-like host stars from F0V to K7V. We update a well-tested 1D climate-photochemistry model to explore the changes of a planetary environment for different surfaces for different host stars. Our results show that using a wavelength-dependent surface albedo is critical for modelling potentially habitable rocky exoplanets.

scholarly journals Monitoring of the D doublet of neutral sodium during transits of two ‘evaporating’ planets

2019 ◽  
Vol 485 (3) ◽  
pp. 3876-3886 ◽  
Author(s):  
E Gaidos ◽  
T Hirano ◽  
M Ansdell
Keyword(s):  
High Resolution ◽  
Orbital Evolution ◽  
Detection Sensitivity ◽  
Needed Information ◽  
Composition Formation ◽  
Sky Survey ◽  
Instrumental Resolution ◽  
Large Telescopes ◽  
Host Stars ◽  
Neutral Sodium

ABSTRACT Spectroscopic transit detection of constituents in winds from ‘evaporating’ planets on close-in transiting orbits could provide desperately needed information on the composition, formation, and orbital evolution of such objects. We obtained high-resolution optical spectra of the host stars during a single transit of Kepler-1520b and two transits of K2-22b to search for transient, Doppler-shifted absorption in the D lines of neutral sodium. Sodium should be released in the same silicate vapour wind that lofts the dust responsible for the periodic ‘dips’ in the light curve. We do not detect any absorption lines with depths >30 per cent at the predicted Doppler-shifted wavelengths during any of the transits. Detection sensitivity is limited by instrumental resolution that dilutes the saturated lines, and blurring of the lines by Doppler acceleration due to the short orbital period of the planet and long integration times for these faint stars. A model of neutral sodium production, escape, and ionization by UV radiation suggests that clouds of partially ionized sodium that are comparable in size to the host stars and optically thick in the D lines could accompany the planets. We consider the prospects for future detections brought about by the TESS all-sky survey of brighter stars and the advent of high-resolution spectrographs on Extremely Large Telescopes.

scholarly journals Exoplanet Searches in the Habitable Zone with Gravitational Microlensing

2012 ◽  
Vol 8 (S293) ◽  
pp. 36-38
Author(s):  
Alexander F. Zakharov ◽  
Gabriele Ingrosso ◽  
Francesco De Paolis ◽  
Achille A. Nucita ◽  
Francesco Strafella ◽  
...  
Keyword(s):  
Relative Position ◽  
Theoretical Models ◽  
Polarization Angle ◽  
Habitable Zone ◽  
Polarization Measurements ◽  
Additional Information ◽  
Spectral Shifts ◽  
Gravitational Microlensing ◽  
Earth Like Planets ◽  
Host Stars

AbstractThere are different methods for finding exoplanets such as radial spectral shifts, astrometrical measurements, transits, timing, etc. Gravitational microlensing (including pixel-lensing) is among the most promising techniques with the potential of detecting Earth-like planets at distances about a few astronomical units from their host stars. Here we emphasize the importance of polarization measurements which can help to resolve degeneracies in theoretical models. In particular, the polarization angle could give additional information about the relative position of the lens with respect to the source.

scholarly journals Venus: key to understanding the evolution of terrestrial planets

2021 ◽  
Author(s):  
Colin F. Wilson ◽  
Thomas Widemann ◽  
Richard Ghail
Keyword(s):  
High Temperature ◽  
High Resolution ◽  
Radar Imaging ◽  
Space Science ◽  
Interior Surface ◽  
Extended Surface ◽  
Earth Like Planets ◽  
Orbital Mission

AbstractIn this paper, originally submitted in answer to ESA’s “Voyage 2050” call to shape the agency’s space science missions in the 2035–2050 timeframe, we emphasize the importance of a Venus exploration programme for the wider goal of understanding the diversity and evolution of habitable planets. Comparing the interior, surface, and atmosphere evolution of Earth, Mars, and Venus is essential to understanding what processes determined habitability of our own planet and Earth-like planets everywhere. This is particularly true in an era where we expect thousands, and then millions, of terrestrial exoplanets to be discovered. Earth and Mars have already dedicated exploration programmes, but our understanding of Venus, particularly of its geology and its history, lags behind. Multiple exploration vehicles will be needed to characterize Venus’ richly varied interior, surface, atmosphere and magnetosphere environments. Between now and 2050 we recommend that ESA launch at least two M-class missions to Venus (in order of priority): a geophysics-focussed orbiter (the currently proposed M5 EnVision orbiter – [1] – or equivalent); and an in situ atmospheric mission (such as the M3 EVE balloon mission – [2]). An in situ and orbital mission could be combined in a single L-class mission, as was argued in responses to the call for L2/L3 themes [3–5]. After these two missions, further priorities include a surface lander demonstrating the high-temperature technologies needed for extended surface missions; and/or a further orbiter with follow-up high-resolution surface radar imaging, and atmospheric and/or ionospheric investigations.

scholarly journals Carbonate-silicate cycle predictions of Earth-like planetary climates and testing the habitable zone concept

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Owen R. Lehmer ◽  
David C. Catling ◽  
Joshua Krissansen-Totton
Keyword(s):  
Liquid Water ◽  
Physicochemical Parameters ◽  
Silicate Weathering ◽  
Habitable Zone ◽  
Two Dimensional ◽  
Land Area ◽  
Incident Flux ◽  
Earth Like Planets ◽  
Surface Liquid ◽  
Log Linear

AbstractIn the conventional habitable zone (HZ) concept, a CO2-H2O greenhouse maintains surface liquid water. Through the water-mediated carbonate-silicate weathering cycle, atmospheric CO2 partial pressure (pCO2) responds to changes in surface temperature, stabilizing the climate over geologic timescales. We show that this weathering feedback ought to produce a log-linear relationship between pCO2 and incident flux on Earth-like planets in the HZ. However, this trend has scatter because geophysical and physicochemical parameters can vary, such as land area for weathering and CO2 outgassing fluxes. Using a coupled climate and carbonate-silicate weathering model, we quantify the likely scatter in pCO2 with orbital distance throughout the HZ. From this dispersion, we predict a two-dimensional relationship between incident flux and pCO2 in the HZ and show that it could be detected from at least 83 (2σ) Earth-like exoplanet observations. If fewer Earth-like exoplanets are observed, testing the HZ hypothesis from this relationship could be difficult.

Ultrastable high-resolution spectrographs for large telescopes

1998 ◽  
Author(s):  
Francisco Diego ◽  
Ian A. Crawford ◽  
David D. Walker
Keyword(s):  
High Resolution ◽  
Large Telescopes

The habitable zone of Earth-mass planets around 47 UMa: results for land and water worlds

2003 ◽  
Vol 2 (1) ◽  
pp. 35-39 ◽  
Author(s):  
S. Franck ◽  
M. Cuntz ◽  
W. von Bloh ◽  
C. Bounama
Keyword(s):  
Surface Water ◽  
System Approach ◽  
Distinct Type ◽  
Integrated System ◽  
Habitable Zone ◽  
Stable Orbit ◽  
The Earth ◽  
Earth Like Planets ◽  
Very High

In a previous paper, we showed that Earth-type habitable planets around 47 UMa are in principle possible if a distinct set of conditions is warranted. These conditions include that the Earth-type planets have successfully formed and are orbitally stable and, in addition, that the 47 UMa star–planet system is relatively young ([lsim ]6 Gyr). We now extend this study by considering Earth-like planets with different land/ocean coverages. This study is again based on the so-called integrated system approach, which describes the photosynthetic biomass production taking into account a variety of climatological, biogeochemical and geodynamical processes. This approach implies a special characterization of the habitable zone defined for a distinct type of planet. We show that the likelihood of finding a habitable Earth-like planet on a stable orbit around 47 UMa critically depends on the percentage of the planetary land/ocean coverage. The likelihood is significantly increased for planets with a very high percentage of ocean surface (‘water worlds’).

scholarly journals Quiescent and flaring lyman-α radiation of host stars and effects on exoplanets

2015 ◽  
Vol 11 (S320) ◽  
pp. 391-396
Author(s):  
Jeffrey L. Linsky ◽  
Kevin France ◽  
Yamila Miguel ◽  
Lisa Kaltenegger
Keyword(s):  
Emission Lines ◽  
Late Type ◽  
Chemical Abundances ◽  
Interstellar Absorption ◽  
Ultraviolet Spectra ◽  
M Stars ◽  
Host Stars ◽  
Stars Flare ◽  
Photochemical Models

AbstractLyman-α radiation dominates the ultraviolet spectra of G, K, and M stars and is a major photodissociation source for H2O, CO2, and CH4 in the upper atmospheres of exoplanets. We obtain intrinsic Lyman-α line fluxes for late-type stars by correcting for interstellar absorption or by scaling from other spectroscopic observables. When stars flare, all emission lines brighten by large factors as shown by HST spectra. We describe photochemical models of the atmosphere of the mini-Neptune GJ 436b (Miguel et al. 2015) that show the effects of flaring Lyman-α fluxes on atmospheric chemical abundances.

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