TRANSITS OF EARTH-LIKE PLANETS

By L. Kaltenegger, Wesley A. Traub. 2009

263 citations recorded by the source corpus.

Transmission spectroscopy of Earth-like exoplanets is a potential tool for habitability screening. Transiting planets are present-day “Rosetta Stones” for understanding extrasolar planets because they offer the possibility to characterize giant planet atmospheres and should provide an access to biomarkers in the atmospheres of Earth-like exoplanets, once they are detected. Using the Earth itself as a proxy we show the potential and limits of the transiting technique to detect biomarkers on an Earth-analog exoplanet in transit. We quantify the Earth's cross section as a function of wavelength, and show the effect of each atmospheric species, aerosol, and Rayleigh scattering. Clouds do not significantly affect this picture because the opacity of the lower atmosphere from aerosol and Rayleigh losses dominates over cloud losses. We calculate the optimum signal-to-noise ratio for spectral features in the primary eclipse spectrum of an Earth-like exoplanet around a Sun-like star and also M stars, for a 6.5 m telescope in space. We find that the signal-to-noise values for all important spectral features are on the order of unity or less per transit—except for the closest stars—making it difficult to detect such features in one single transit, and implying that coadding of many transits will be essential.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/7fc637bf5f5cf4ba74d9f198cf9e24798a09d0f3

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Citations in the corpus

Characterization of the K2-18 multi-planetary system with HARPS: A habitable zone super-Earth and discovery of a second, warm super-Earth on a non-coplanar orbit (2017, background): “…of ∆F/F ∼ 10Hrp/R2s ∼ 230 ppm where H = kBTeq/µg is the atmospheric scale height, Teq is the planet’s equilibrium temperature set by the stellar insolation, µ is the mean molecular weight of the atmosphere, and g is the surface gravity (Miller-Ricci et al. 2009; Kaltenegger & Traub 2009).”
Exoplanet Atmospheres: Physical Processes (2010, background): “For a comparison of Earth-like planet atmospheres around both M stars and Sun-like stars see Kaltenegger & Traub (2009).”
THE FLAT TRANSMISSION SPECTRUM OF THE SUPER-EARTH GJ1214b FROM WIDE FIELD CAMERA 3 ON THE HUBBLE SPACE TELESCOPE (2011, methodology): “Prospects for GJ1214b Future observations with the James Webb Space Telescope (Deming et al. 2009; Kaltenegger & Traub 2009), one of the immense next generation ground-based telescopes (GMT, TMT, ELT; see Ehrenreich et al. 2006), or possibly even a dedicated campaign with current facilities, could…”
Observations of Transiting Exoplanets with the James Webb Space Telescope (JWST) (2014, background): “Programs challenging JWST’s ultimate levels of precision should also be carried out, e.g., detection H2O, CO2, or O3 via transmission or emission spectroscopy from potentially (or nearly) habitable super-Earths (Kaltenegger & Traub 2009; Deming et al. 2009).”
Stellar Flares from the First TESS Data Release: Exploring a New Sample of M Dwarfs (2019, background): “Second, their small radii and low temperatures enable the detection and atmospheric characterization of habitable planets on short orbits (Kaltenegger & Traub 2009).”
Potential Biosignatures in Super-Earth Atmospheres (2010, methodology): “To validate our approach, we performed SNR calculations foreveral modern Earth transmis- sion features, which were also performed by Kaltenegger & Traub (2009) (their Table 2, single transit events).”
The Transit Light Source Effect: False Spectral Features and Incorrect Densities for M-dwarf Transiting Planets (2017, methodology): “For each spectral type, we calculated the surface gravity g from the stellar masses and radii summarized by Kaltenegger & Traub (2009) and adopted the stellar effective temperature from that same work as the photosphere temperature Tphot.”
A FRAMEWORK FOR QUANTIFYING THE DEGENERACIES OF EXOPLANET INTERIOR COMPOSITIONS (2009, background): “Observations will be extremely challenging, even with multiple transits (Kaltenegger & Traub 2009; Deming et al. 2009).”
ABIOTIC OZONE AND OXYGEN IN ATMOSPHERES SIMILAR TO PREBIOTIC EARTH (2014, background): “However, if this instrument is used to characterize transit spectra of any potentially-habitable super-Earth planets (Kaltenegger and Traub, 2009), the cautions above should be taken into consideration. measurements with a SNR above 17 at 1.7 µm and complete removal of the overlapping…”
A NEARBY M STAR WITH THREE TRANSITING SUPER-EARTHS DISCOVERED BY K2 (2015, background): “In addition, some of K2’s M-dwarf planets orbit stars bright enough for atmospheric characterization via JWST transmission or emission spectroscopy (Kaltenegger & Traub 2009; Batalha et al. 2013; Beichman et al. 2014).”
FINDING EXTRATERRESTRIAL LIFE USING GROUND-BASED HIGH-DISPERSION SPECTROSCOPY (2013, methodology): “…than the Earth atmospheric scale height of H = 8 km. Convolved to low spectral resolution, the oxygen transmission signal decreases to 10–20 km—similar to that calculated in earlier studies (Tinetti 2006; Ehrenreich et al. 2006; Kaltenegger & Traub 2009; Rauer et al. 2011; Palle et al. 2011).”
How to Characterize Habitable Worlds and Signs of Life (2017, methodology): “Panel dmodified from Figure 3 in Kaltenegger & Traub (2009).”