In this white paper, we recommend the European Space Agency plays a proactive role in developing a global collaborative effort to construct a large high-contrast imaging space telescope, e.g. as... Show moreIn this white paper, we recommend the European Space Agency plays a proactive role in developing a global collaborative effort to construct a large high-contrast imaging space telescope, e.g. as currently under study by NASA. Such a mission will be needed to characterize a sizable sample of temperate Earth-like planets in the habitable zones of nearby Sun-like stars and to search for extraterrestrial biological activity. We provide an overview of relevant European expertise, and advocate ESA to start a technology development program towards detecting life outside the Solar system. Show less
Exoplanet science is one of the most thriving fields of modern astrophysics. A major goal is the atmospheric characterization of dozens of small, terrestrial exoplanets in order to search for... Show moreExoplanet science is one of the most thriving fields of modern astrophysics. A major goal is the atmospheric characterization of dozens of small, terrestrial exoplanets in order to search for signatures in their atmospheres that indicate biological activity, assess their ability to provide conditions for life as we know it, and investigate their expected atmospheric diversity. None of the currently adopted projects or missions, from ground or in space, can address these goals. In this White Paper we argue that a large space-based mission designed to detect and investigate thermal emission spectra of terrestrial exoplanets in the MIR wavelength range provides unique scientific potential to address these goals and surpasses the capabilities of other approaches. While NASA might be focusing on large missions that aim to detect terrestrial planets in reflected light, ESA has the opportunity to take leadership and spearhead the development of a large MIR exoplanet mission within the scope of the "Voyage 2050" long-term plan establishing Europe at the forefront of exoplanet science for decades to come. Given the ambitious science goals of such a mission, additional international partners might be interested in participating and contributing to a roadmap that, in the long run, leads to a successful implementation. A new, dedicated development program funded by ESA to help reduce development and implementation cost and further push some of the required key technologies would be a first important step in this direction. Ultimately, a large MIR exoplanet imaging mission will be needed to help answer one of mankind's most fundamental questions: "How unique is our Earth?" Show less
This thesis presents observations of exoplanets orbiting very close to their parent star, with a particular focus on a novel technique for characterizing their atmospheres. This is based on the use... Show moreThis thesis presents observations of exoplanets orbiting very close to their parent star, with a particular focus on a novel technique for characterizing their atmospheres. This is based on the use of high-resolution spectroscopy from the ground. The first detection of the atmosphere of a non-transiting planet is presented, together with the determination of its mass and orbital inclination. Moreover, it is shown that high-dispersion spectroscopy is very effective in recognizing molecular species, measuring their relative abundances, and determining whether temperature increases or decreases with altitude in the observed planetary atmospheres. The method also led to the measurement of the rotational period of a transiting exoplanet, which was found to be tidally locked, in line with theoretical predictions. Finally, the evidence for the disintegration of a small, rocky planet candidate in the Kepler database is presented. This result was obtained by fitting the light curve of the object with a model of a trailing tail of dust. Show less
Werkhoven, T.I.M. van; Brogi, M.; Snellen, I.A.G.; Keller, C.U. 2014
We report a 4.8{$σ$} detection of water absorption features in the day side spectrum of the hot Jupiter HD 189733 b. We used high-resolution (R {\tilde} 100 000) spectra taken at 3.2 {$μ$}m with... Show moreWe report a 4.8{$σ$} detection of water absorption features in the day side spectrum of the hot Jupiter HD 189733 b. We used high-resolution (R {\tilde} 100 000) spectra taken at 3.2 {$μ$}m with CRIRES on the VLT to trace the radial-velocity shift of the water features in the planet's day side atmosphere during 5 h of its 2.2 d orbit as it approached secondary eclipse. Despite considerable telluric contamination in this wavelength regime, we detect the signal within our uncertainties at the expected combination of systemic velocity (V\_sys=-3\^{}$\{$+5$\}$\_$\{$-6$\}$ km s$^{-1}$) and planet orbital velocity (K\_p=154\^{}$\{$+14$\}$\_$\{$-10$\}$ km s$^{-1}$), and determine a H$_{2}$O line contrast ratio of (1.3 {\plusmn} 0.2) {\times} 10$^{-3}$ with respect to the stellar continuum. We find no evidence of significant absorption or emission from other carbon-bearing molecules, such as methane, although we do note a marginal increase in the significance of our detection to 5.1{$σ$} with the inclusion of carbon dioxide in our template spectrum. This result demonstrates that ground-based, high-resolution spectroscopy is suited to finding not just simple molecules like CO, but also to more complex molecules like H$_{2}$O even in highly telluric contaminated regions of the Earth's transmission spectrum. It is a powerful tool that can be used for conducting an immediate census of the carbon- and oxygen-bearing molecules in the atmospheres of giant planets, and will potentially allow the formation and migration history of these planets to be constrained by the measurement of their atmospheric C/O ratios. Show less
Mooij, E. de; Brogi, M.; Kok, R. de; Snellen, I.A.G.; Kenworthy, M.A.; Karjalainen, R. 2013
Context. In recent years, day-side emission from about a dozen hot Jupiters has been detected through ground-based secondary eclipse observations in the near-infrared. These near-infrared... Show moreContext. In recent years, day-side emission from about a dozen hot Jupiters has been detected through ground-based secondary eclipse observations in the near-infrared. These near-infrared observations are vital for determining the energy budgets of hot Jupiters, since they probe the planet's spectral energy distribution near its peak. Aims: The aim of this work is to measure the K$_s$-band secondary eclipse depth of WASP-33b, the first planet discovered to transit an A-type star. This planet receives the highest level of irradiation of all transiting planets discovered to date. Furthermore, its host-star shows pulsations and is classified as a low-amplitude {$delta$} Scuti. Methods: As part of our GROUnd-based Secondary Eclipse (GROUSE) project we have obtained observations of two separate secondary eclipses of WASP-33b in the K$_s$-band using the LIRIS instrument on the William Herschel Telescope (WHT). The telescope was significantly defocused to avoid saturation of the detector for this bright star (K ~{} 7.5). To increase the stability and the cadence of the observations, they were performed in staring mode. We collected a total of 5100 and 6900 frames for the first and the second night respectively, both with an average cadence of 3.3 s. Results: On the second night the eclipse is detected at the 12 -{$σ$} level, with a measured eclipse depth of 0.244$_{-0.020}$$^{+0.027}$%. This eclipse depth corresponds to a brightness temperature of 3270$_{-160}$$^{+115}$ K. The measured brightness temperature on the second night is consistent with the expected equilibrium temperature for a planet with a very low albedo and a rapid re-radiation of the absorbed stellar light. For the other night the short out-of-eclipse baseline prevents good corrections for the stellar pulsations and systematic effects, which makes this dataset unreliable for eclipse depth measurements. This demonstrates the need of getting a sufficient out-of-eclipse baseline. Appendix A is available in electronic form at http://www.aanda.orgLight curves are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/550/A54Show less
Mooij, E. de; Brogi, M.; Kok, R.; Snellen, I.A.G.; Croll, B.; Jayawardhana, R.; ... ; Houdt, J. van 2013
We investigate the atmosphere of GJ1214b, a transiting super-Earth planet with a low mean density, by measuring its transit depth as a function of wavelength in the blue optical portion of the... Show moreWe investigate the atmosphere of GJ1214b, a transiting super-Earth planet with a low mean density, by measuring its transit depth as a function of wavelength in the blue optical portion of the spectrum. It is thought that this planet is either a mini-Neptune, consisting of a rocky core with a thick, hydrogen-rich atmosphere, or a planet with a composition dominated by water. Most observations favor a water-dominated atmosphere with a small scale-height, however, some observations indicate that GJ1214b could have an extended atmosphere with a cloud layer muting the molecular features. In an atmosphere with a large scale-height, Rayleigh scattering at blue wavelengths is likely to cause a measurable increase in the apparent size of the planet toward the blue. We observed the transit of GJ1214b in the B band with the FOcal Reducing Spectrograph at the Very Large Telescope and in the g band with both ACAM on the William Herschel Telescope (WHT) and the Wide Field Camera at the Isaac Newton Telescope (INT). We find a planet-to-star radius ratio in the B band of 0.1162 {plusmn} 0.0017, and in the g band 0.1180 {plusmn} 0.0009 and 0.1174 {plusmn} 0.0017 for the WHT and INT observations, respectively. These optical data do not show significant deviations from previous measurements at longer wavelengths. In fact, a flat transmission spectrum across all wavelengths best describes the combined observations. When atmospheric models are considered, a small scale-height water-dominated model fits the data best. Show less
