Detection of carbon monoxide in the high-resolution day-side spectrum of the exoplanet HD 189733b

[Abridged] After many attempts over more than a decade, high-resolution spectroscopy has recently delivered its first detections of molecular absorption in exoplanet atmospheres, both in transmission and thermal emission spectra. Targeting the combined signal from individual lines in molecular bands, these measurements use variations in the planet radial velocity to disentangle the planet signal from telluric and stellar contaminants. In this paper we apply high resolution spectroscopy to probe molecular absorption in the day-side spectrum of the bright transiting hot Jupiter HD 189733b. We observed HD 189733b with the CRIRES high-resolution near-infrared spectograph on the Very Large Telescope during three nights. We detect a 5-sigma absorption signal from CO at a contrast level of ~4.5e-4 with respect to the stellar continuum, revealing the planet orbital radial velocity at 154+4/-3 km s-1. This allows us to solve for the planet and stellar mass in a similar way as for stellar eclipsing binaries, resulting in Ms= 0.846+0.068/-0.049 Msun and Mp= 1.162+0.058/-0.039 MJup. No significant absorption is detected from H2O, CO2 or CH4 and we determined upper limits on their line contrasts here. The detection of CO in the day-side spectrum of HD 189733b can be made consistent with the haze layer proposed to explain the optical to near-infrared transmission spectrum if the layer is optically thin at the normal incidence angles probed by our observations, or if the CO abundance is high enough for the CO absorption to originate from above the haze. Our non-detection of CO2 at 2.0 micron is not inconsistent with the deep CO2 absorption from low resolution NICMOS secondary eclipse data in the same wavelength range. If genuine, the absorption would be so strong that it blanks out any planet light completely in this wavelength range, leaving no high-resolution signal to be measured.Comment: A&A, accepted for publication. Fig.1 reduced in qualit

Detection of water absorption in the day side atmosphere of HD 189733 b using ground-based high-resolution spectroscopy at 3.2 microns

We report a 4.8 sigma detection of water absorption features in the day side spectrum of the hot Jupiter HD 189733 b. We used high-resolution (R~100,000) spectra taken at 3.2 microns 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 (Vsys=-3 +5-6 km/s) and planet orbital velocity (Kp=154 +14-10 km/s), and determine a H2O line contrast ratio of (1.3+/-0.2)x10^-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 sigma 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 H2O 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.Comment: 5 pages, 4 figures, accepted for publication in MNRAS Letter

The signature of orbital motion from the dayside of the planet tau Bootis b

The giant planet orbiting tau Bootis was among the first extrasolar planets to be discovered through the reflex motion of its host star. It is one of the brightest known and most nearby planets with an orbital period of just a few days. Over the course of more than a decade, measurements of its orbital inclination have been announced and refuted, and have subsequently remained elusive until now. Here we report on the detection of carbon monoxide absorption in the thermal day-side spectrum of tau Bootis b. At a spectral resolution of R~100,000, we trace the change in the radial velocity of the planet over a large range in phase, determining an orbital inclination of i=44.5+-1.5 degrees and a true planet mass of 5.95+-0.28 MJup. This result extends atmospheric characterisation to non-transiting planets. The strong absorption signal points to an atmosphere with a temperature that is decreasing towards higher altitudes. This is a stark contrast to the temperature inversion invoked for other highly irradiated planets, and supports models in which the absorbing compounds believed to cause such atmospheric inversions are destroyed by the ultraviolet emission from the active host star.Comment: To appear in the June 28 issue of Nature: main article + supplementary informatio

A chemical survey of exoplanets with ARIEL

Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the essential nature of these exoplanets remains largely mysterious: there is no known, discernible pattern linking the presence, size, or orbital parameters of a planet to the nature of its parent star. We have little idea whether the chemistry of a planet is linked to its formation environment, or whether the type of host star drives the physics and chemistry of the planet’s birth, and evolution. ARIEL was conceived to observe a large number (~1000) of transiting planets for statistical understanding, including gas giants, Neptunes, super-Earths and Earth-size planets around a range of host star types using transit spectroscopy in the 1.25–7.8 μm spectral range and multiple narrow-band photometry in the optical. ARIEL will focus on warm and hot planets to take advantage of their well-mixed atmospheres which should show minimal condensation and sequestration of high-Z materials compared to their colder Solar System siblings. Said warm and hot atmospheres are expected to be more representative of the planetary bulk composition. Observations of these warm/hot exoplanets, and in particular of their elemental composition (especially C, O, N, S, Si), will allow the understanding of the early stages of planetary and atmospheric formation during the nebular phase and the following few million years. ARIEL will thus provide a representative picture of the chemical nature of the exoplanets and relate this directly to the type and chemical environment of the host star. ARIEL is designed as a dedicated survey mission for combined-light spectroscopy, capable of observing a large and well-defined planet sample within its 4-year mission lifetime. Transit, eclipse and phase-curve spectroscopy methods, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allow us to measure atmospheric signals from the planet at levels of 10–100 part per million (ppm) relative to the star and, given the bright nature of targets, also allows more sophisticated techniques, such as eclipse mapping, to give a deeper insight into the nature of the atmosphere. These types of observations require a stable payload and satellite platform with broad, instantaneous wavelength coverage to detect many molecular species, probe the thermal structure, identify clouds and monitor the stellar activity. The wavelength range proposed covers all the expected major atmospheric gases from e.g. H2O, CO2, CH4 NH3, HCN, H2S through to the more exotic metallic compounds, such as TiO, VO, and condensed species. Simulations of ARIEL performance in conducting exoplanet surveys have been performed – using conservative estimates of mission performance and a full model of all significant noise sources in the measurement – using a list of potential ARIEL targets that incorporates the latest available exoplanet statistics. The conclusion at the end of the Phase A study, is that ARIEL – in line with the stated mission objectives – will be able to observe about 1000 exoplanets depending on the details of the adopted survey strategy, thus confirming the feasibility of the main science objectives.Peer reviewedFinal Published versio

Detecting life outside our solar system with a large high-contrast-imaging mission

This is the final version. Available from ESA via the link in this recordESA Voyage 2050 White PaperIn 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

Detecting life outside our solar system with a large high-contrast-imaging mission

In this White Paper, which was submitted in response to the European Space Agency (ESA) Voyage 2050 Call, we recommend the ESA 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.Publisher PDFPeer reviewe

Vector-apodizing phase plate coronagraph: design, current performance, and future development [Invited]

Instrumentatio

ESA Voyage 2050 White Paper: Detecting life outside our solar system with a large high-contrast-imaging mission

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 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.Stars and planetary systemsInstrumentatio