Hot Atmosphere Research Articles

ExoMol at 10

Abstract For ten years, the ExoMol database of molecular line lists has provided vital spectroscopic data for the study of hot atmospheres. Jonathan Tennyson and Sergei N Yurchenko reflect on what the prject has achieved.

Spherically symmetric model atmospheres using approximate lambda operators

Context. Clumping is a common property of stellar winds and is being incorporated to a solution of the radiative transfer equation coupled with kinetic equilibrium equations. However, in static hot model atmospheres, clumping and its influence on the temperature and density structures have not been considered and analysed at all to date. This is in spite of the fact that clumping can influence the interpretation of resulting spectra, as many inhomogeneities can appear there; for example, as a result of turbulent motions. Aims. We aim to investigate the effects of clumping on atmospheric structure for the special case of a static, spherically symmetric atmosphere assuming microclumping and a 1D geometry. Methods. Static, spherically symmetric, non-LTE (local thermodynamic equilibrium) model atmospheres were calculated using the recent version of our code, which includes optically thin clumping. The matter is assumed to consist of dense clumps and a void interclump medium. Clumping is considered by means of clumping and volume filling factors, assuming all clumps are optically thin. Enhanced opacity and emissivity in clumps are multiplied by a volume filling factor to obtain their mean values. These mean values are used in the radiative transfer equation. Equations of kinetic equilibrium and the thermal balance equation use clump values of densities. Equations of hydrostatic and radiative equilibrium use mean values of densities. Results. The atmospheric structure was calculated for selected stellar parameters. Moderate differences were found in temperature structure. However, clumping causes enhanced continuum radiation for the Lyman-line spectral region, while radiation in other parts of the spectrum is lower, depending on the adopted model. The atomic level departure coefficients are influenced by clumping as well.

The Near-stellar Environment of Class 0 Protostars: A First Look with Near-infrared Spectroscopy

Abstract We present near-infrared K-band spectra for a sample of seven Class 0 protostars in the Perseus and Orion star-forming regions. We detect Brγ, CO overtone, and H2 emission, features that probe the near-circumstellar environment of the protostar and reveal evidence of magnetospheric accretion, a hot inner disk atmosphere, and outflows, respectively. Comparing the properties of these features with those of Class I sources from the literature, we find that their Brγ emission and CO emission are generally consistent in strength and velocity width. The Brγ line profiles are broad and centrally peaked, with FWHMs of ∼200 km s−1 and wings extending to ∼300 km s−1. The line ratios of our H2 emission features, which are spatially extended for some sources, are consistent with shock excitation and indicate the presence of strong jets or a disk wind. Within our small sample, the frequency of CO band emission (∼67%) is high relative to that of Class I samples (∼15%), indicating that Class 0 sources have high inner disk accretion rates, similar to those of the most actively accreting Class I sources. Collectively, our results suggest that Class 0 sources have similar accretion mechanisms to the more evolved classes, with strong organized stellar magnetic fields established at the earliest observable stage of evolution.

Genesis of a CO2-rich and H2O-depleted atmosphere from Earth's early global magma ocean.

The magma ocean was a important reservoir for Earth’s primary volatiles. Understanding the volatile fluxes between the early atmosphere and the magma ocean is fundamental for quantifying the volatile budget of our planet. Here we investigate the vaporization of carbon and hydrogen at the boundary between the magma ocean and the thick, hot early atmosphere using first-principles molecular dynamics calculations. We find that carbon is rapidly devolatilized, while hydrogen mostly remains dissolved in the magma during the existence of a thick silicate-bearing atmosphere. In the early stages of the magma ocean, the atmosphere would have contained significantly more carbon than hydrogen, and the high concentrations of carbon dioxide would have prolonged the cooling time of early Earth.

Elemental Abundances of the Hot Atmosphere of Luminous Infrared Galaxy Arp 299

Abstract Hot atmospheres of massive galaxies are enriched with metals. Elemental abundances measured in the X-ray band have been used to study the chemical enrichment of supernova remnants, elliptical galaxies, groups, and clusters of galaxies. Here we measure the elemental abundances of the hot atmosphere of luminous infrared galaxy Arp 299 observed with XMM-Newton. To measure the abundances in the hot atmosphere, we use a multi-temperature thermal plasma model, which provides a better fit to the Reflection Grating Spectrometer data. The observed Fe/O abundance ratio is subsolar, while those of Ne/O and Mg/O are slightly above solar. Core-collapse supernovae (SNcc) are the dominant metal factory of elements like O, Ne, and Mg. We find some deviations between the observed abundance patterns and theoretical ones from a simple chemical enrichment model. One possible explanation is that massive stars with M ⋆ ≳ 23–27 M ⊙ might not explode as SNcc and enrich the hot atmosphere. This is in accordance with the missing massive SNcc progenitors problem, where very massive progenitors M ⋆ ≳ 18 M ⊙ of SNcc have not been clearly detected. It is also possible that theoretical SNcc nucleosynthesis yields of Mg/O yields are underestimated.

Study on combustion control of a methanol SICI engine

Spark induced compression ignition (SICI) combined mode combustion can effectively solve the problems existing in homogeneous charge compression ignition (HCCI) combustion, and expand its operation range. The SICI combined combustion of methanol is divided into two combustion stages and has the characteristics of spark ignition (SI) and compression ignition (CI) combustion modes at the same time. This paper studies the SICI combustion mode of methanol from two aspects: simulation and experiment. The simulation results show that with the increase of the wall temperature, it indirectly affected the SICI combined mode combustion by affecting the hot atmosphere in the cylinder, which shortened the whole combustion duration, the SI and CI duration, it had little effect on the combustion ratio of SI and CI. The bench test results show that the methanol engine can obtain stable SICI combined mode combustion mode under the conditions of appropriate intake temperature and suitable ignition timing. From the comparison of three combustion modes of methanol, the results show that the cyclic variability of SICI combustion is the smallest. With the increase of inlet air temperature and the delay of ignition, the BP of SICI combustion at methanol starting point moves backward, the CI combustion rate decreases, but the SI combustion duration changes slightly, and the compression ignition ratio decreases. In the SICI combustion mode of methanol engine, with the increase of intake temperature, NOx emission increases, HC and CO emission decreases. With the advance of ignition timing, CO emission decreases, HC and NOx emission increases.

Effects of Storage Time and Pre-Etching Treatment of CR-39 Detectors on Their Response to Alpha Radiation Exposure

Radon passive monitors based on solid state nuclear track detectors (SSNTD), especially CR-39, are widely used in radon and thoron studies. They may be subjected to the influence of external factors, like changing of temperature, humidity, and pressure, both before and during the measurement. Evaluation of the exposed detectors involves chemical processing, whose conditions also influence the measurement results. The aim of this study was to check several factors, as to whether they may modify the response of CR-39 detector: concerning the phase before evaluation, storage time, and temperature during storage; and concerning the evaluation procedure, etching time, and pre-etching treatment using hot water and carbon dioxide atmosphere. Two experiments were conducted by irradiation of CR-39 detectors using alpha particles emitted from a mono-energetic 241Am source and exposed in radon atmosphere. Track density dependence of the age of production was found to be statistically not significant. On the other hand, pre-etching treatment using hot water and carbon dioxide with different etching times showed statistically significant effects on track area, track sensitivity, and roundness. It was concluded that there are simple methods to increase performance of nuclear track detectors, and that storage time is not a factor of concern.

A model for the kinetics of high-temperature reactions between polydisperse volcanic ash and SO2 gas

AbstractRapid calcium diffusion occurs in rhyolitic volcanic ash particles exposed to hot SO2 atmospheres. Such chemical transport is important immediately following fragmentation, during proximal transport in eruption plumes and during percolative gas transport through a permeable volcanic edifice. Here we analyze published results of experiments designed to constrain the kinetics of this process. The experiments involve crushed rhyolitic glass particles tumbled in SO2-bearing atmospheres at a wide range of relevant temperatures. We find that the particle-gas reaction is fed by calcium diffusion from the bulk to the particle surfaces where calcium-sulfate crystals grow. The calcium flux is accommodated by local iron oxidation state changes. This process results in time-dependent concentrations of surface calcium that are leachable in aqueous solutions. Those leachate concentrations represent a proxy for the diffusive flux of Ca2+ out of the particle to form the surface deposits. We formulate a mathematical framework to convolve the starting particle size distributions with the solution to Fickian one-dimensional diffusion to find a weighted polydisperse result. Using this framework, we minimize for a temperature-dependent calcium diffusivity and compare our results with published calcium diffusivity data. We demonstrate that calcium diffusivity in rhyolite can be decomposed into two regimes: (1) a high-temperature regime in which the diffusivity is given by the Eyring equation and (2) a low-temperature regime more relevant to rhyolite volcanism and these gas-ash reactions. As a further test of our model, we compare the output against spatially resolved data for the calcium gradients in the experimental particles. Our analysis suggests that surface reaction rates are rapid compared with the diffusion of calcium from the particle to the surface, such that full diffusion models must be solved to predict the rhyolite-SO2 reaction. We conclude by suggesting how this framework could be used to make quantitative predictions of sulfur budgets and iron oxidation during rhyolitic eruptions.

Stark broadening for Br VI and Kr V-VII lines in hot star atmospheres

Context. This paper provides missing Stark broadening of the Br VI and Kr V-VII lines recently discovered in the ultraviolet spectrum of the hot white dwarf RE 0503–289 and investigates the importance of the Stark broadening mechanism versus the Doppler mechanism in that star. As far as we know, this is the first time that Stark widths of Br VI and Kr V-VII lines have been calculated. Aims. The recent discovery of new lines of Br VI and Kr V-VII encourages us to provide their Stark broadening to enrich the STARK-B database and for use in interpretations of the observed spectra. Methods. We used our quantum mechanical method for calculating electron impact broadening to provide Stark widths. The method starts with an evaluation of the structure and collision parameters using the University College London codes SUPERSTRUCTURE/DISTORTED WAVE/JAJOM, which are adapted to the line broadening calculations. We then used the collision parameters to calculate the line widths using our programs. Results. We provide the missing widths of 35 lines of Br VI and Kr V-VII at different electron temperatures and at density Ne = 1017 cm−3. We find that the Stark broadening mechanism is preponderant compared to the Doppler one for almost all the plasma conditions of the considered DO white dwarf atmospheres.

Disequilibrium Chemistry in Exoplanet Atmospheres Observed with the Hubble Space Telescope

Abstract Literature on the theory of exoplanet atmospheric disequilibrium chemistry is rich, although its observational counterpart has yet to emerge beyond the hints provided by a few targets in dedicated studies. We report results from an uniform data reduction and analysis for a catalog of 62 Hubble Space Telescope exoplanet transit spectra where we assess the atmospheric model preference for disequilibrium chemistry (i.e., water vapor is not the dominant absorption spectral signature) over thermal equilibrium chemistry in a comparative planetology context. Where model preference assessment is possible, we find that disequilibrium occurs in about half of the atmospheres, indicating that disequilibrium processes play an important role in the composition of exoplanet atmospheres. While very hot atmospheres, over 1800 K, prefer equilibrium chemistry, we find a clustering of preference for disequilibrium in the 1200–1800 K temperature range. We suggest that UV-augmented thermochemistry may play a significant role for those atmospheres.

Sulfur chemistry in the atmospheres of warm and hot Jupiters

ABSTRACT We present and validate a new network of atmospheric thermochemical and photochemical sulfur reactions. We use a 1D chemical kinetics model to investigate these reactions as part of a broader HCNO chemical network in a series of hot and warm Jupiters. We find that temperatures approaching $1400\, \mathrm{K}$ are favourable for the production of H2S and HS around $\mathrm{10^{-3}\, bar}$ at mixing ratios of around 10−5, an atmospheric level where detection by transit spectroscopy may be possible. At $\mathrm{10^{-3}\, bar}$ and at lower temperatures, down to $1000\, \mathrm{K}$, mixing ratios of S2 can be up to 10−5, at the expense of H2S and HS, which are depleted down to a mixing ratio of 10−7. We also investigate how the inclusion of sulfur can manifest in an atmosphere indirectly, by its effect on the abundance of non-sulfur-bearing species. We find that in a model of the atmosphere of HD 209458 b, the inclusion of sulfur can lower the abundance of NH3, CH4, and HCN by up to two orders of magnitude around $\mathrm{10^{-3}\, bar}$. In the atmosphere of the warm Jupiter 51 Eri b, we additionally find the inclusion of sulfur depletes the peak abundance of CO2 by a factor of 5, qualitatively consistent with prior models. We note that many of the reactions used in the network have poorly determined rate constants, especially at higher temperatures. To obtain an accurate idea of the impact of sulfur chemistry in hot and warm Jupiter atmospheres, experimental measurements of these reaction rates must take place.

Evaluation of Anti-hyperuricemic Activity of the Alcoholic Extract of Dried Capparis moonii Wight Fruits in Wistar Rats

Evaluation of anti-hyperuricemic activity of alcoholic extract of Capparis moonii Wight fruits in Wistar rats, by utilizing Indian caper typically occurring in the Konkan area which grows full-fledged in the hot and dry atmosphere that can be generally found throughout asia. The dried fruits of Capparis moonii W. were extracted using absolute ethanol to get an alcoholic extract. Acute oral toxicity studies were performed to decide the doses. The anti-hyperuricemic activity was estimated by the phenol red excretion in rats and the potassium oxonate induced hyperuricemia models respectively. The alcoholic extract showed dose-dependent mode of action where the higher concentration of 200 mg/kg showed higher amount of retention of phenol red in the blood suggesting that it has better ability to secrete urate out of the body of rats as compared to 100mg/kg. Also in potassium oxonate induced hyperuricemia, similar results were obtained with significant reduction in serum uric acid levels and serum creatinine levels as compared to 100mg/kg. The conclusion of this study was that; it proved that Capparis moonii W. alcoholic extract of the fruits can be beneficial as anti-hyperuricemic treatment agent. It would be encouraging to undertake further studies in future to decode the exact mechanism.

Dual frequency comb absorption spectroscopy of CH4 up to 1000 Kelvin from 6770 to 7570 cm-1

As infrared telescopes are finding evidence of methane in hot exoplanet atmospheres, it is becoming increasingly important to have accurate high-temperature methane absorption models. To evaluate and update several spectroscopic databases (HITRAN2016, HITEMP, ExoMol), we collected laboratory spectra of the methane icosad (6770–7570 cm-1) using a 200 MHz (0.0067 cm-1) dual frequency comb spectrometer. The pure methane data span 18 to 300 Torr and 296 to 1000 K. We found good agreement with the HITRAN2016 model spectrum at room temperature, and substantial mismatch between our spectra and all absorption models at elevated temperature. We present several updates to HITRAN2016 to improve agreement with the measured high-temperature spectra. Specifically, we assign 4283 lower-state energies which had previously been given a default value in HITRAN2016 (EHIT″= 999 cm-1), update existing lower-state energies for 92 features, and add 293 new high-temperature features in order to improve HITRAN2016 above 300 K. Additionally, we update the band-wide line positions by ∼0.001 cm-1, the self-widths by +7%, and we estimate band-averaged temperature-dependence exponents for self-width (0.85) and self-shift (0.58). These measurements are an important step towards merging empirical and theoretical high-temperature methane databases, with the goal of enabling better understanding of exoplanet atmospheres.

Evolution of splashback boundaries and gaseous outskirts: insights from mergers of self-similar galaxy clusters

ABSTRACT A self-similar spherical collapse model predicts a dark matter (DM) splashback and accretion shock in the outskirts of galaxy clusters while missing a key ingredient of structure formation – processes associated with mergers. To fill this gap, we perform simulations of merging self-similar clusters and investigate their DM and gas evolution in an idealized cosmological context. Our simulations show that the cluster rapidly contracts during the major merger and the splashback radius rsp decreases, approaching the virial radius rvir. While in the self-similar model rsp depends on a smooth mass accretion rate parameter Γs, our simulations show that in the presence of mergers, rsp responds to the changes in the total mass accretion rate Γvir, which accounts for both mergers and smooth accretion. The scatter of the Γvir − rsp/rvir relation indicates a generally low Γs ∼ 1 in clusters in cosmological simulations. In contrast to the DM, the hot gaseous atmospheres significantly expand by the merger-accelerated (MA-) shocks formed when the runaway merger shocks overtake the outer accretion shock. After a major merger, the MA-shock radius is larger than rsp by a factor of up to ∼1.7 for Γs ≲ 1 and is ∼rsp for Γs ≳ 3. This implies that (1) mergers could easily generate the MA-shock-splashback offset measured in cosmological simulations, and (2) the smooth mass accretion rate is small in regions away from filaments where MA-shocks reside. We further discuss the shapes of the DM haloes, various shocks, and contact discontinuities formed at different epochs of the merger, and the ram-pressure stripping in cluster outskirts.

Feedback from Active Galactic Nuclei in Galaxy Groups

The co-evolution between supermassive black holes and their environment is most directly traced by the hot atmospheres of dark matter halos. The cooling of the hot atmosphere supplies the central regions with fresh gas, igniting active galactic nuclei (AGN) with long duty cycles. Outflows from the central engine tightly couple with the surrounding gaseous medium and provide the dominant heating source preventing runaway cooling by carving cavities and driving shocks across the medium. The AGN feedback loop is a key feature of all modern galaxy evolution models. Here, we review our knowledge of the AGN feedback process in the specific context of galaxy groups. Galaxy groups are uniquely suited to constrain the mechanisms governing the cooling–heating balance. Unlike in more massive halos, the energy that is supplied by the central AGN to the hot intragroup medium can exceed the gravitational binding energy of halo gas particles. We report on the state-of-the-art in observations of the feedback phenomenon and in theoretical models of the heating-cooling balance in galaxy groups. We also describe how our knowledge of the AGN feedback process impacts galaxy evolution models and large-scale baryon distributions. Finally, we discuss how new instrumentation will answer key open questions on the topic.

PENENTUAN KADAR MANGAN (Mn) PADA AIR GAMBUT SECARA SPEKTROFOTOMETRI UV-Vis DENGAN PERBANDINGAN METODE KURVA KALIBRASI DAN ADISI STANDAR (DETERMINATION OF MANGANESE IN PEAT WATER USING UV-Vis SPECTROPHOTOMETER: COMPARATION OF CALIBRATION OF CURVE AND STANDARD ADDITION METHOD)

Peat water has different characteristics from one location to another. The characteristics referred to include levels of organic matter, pH, conductivity, and turbidity. Based on these differences, it is necessary to research to determine the analytic parameters and the effect of matrix differences on manganese levels using a separate calibration method and standard addition using a Uv-vis spectrophotometer. The determination of manganese was carried out by the persulfate method, that is the oxidation of Mn in water by persulfate in an acidic and hot atmosphere to form MnO4 which is purple-red. The obtained results from the determination of the analytical parameters of the separate calibration method are precision of 7.75% to 63.96%, an accuracy of 0.80% to 5.24%, the linearity of r = 0.997, a detection limit of 0.170 ppm, and a limit of quantification of 0.567 ppm. Meanwhile, the addition method produces a precision of 2.19% to 20.35%, accuracy and linearity at points I, II, III are 10.65% to 25.47% respectively; 20.9% to 26.8%; 2.76% to 27.24% and 0.995; 0.999; 0.995. Linearity in addition as well as in calibration curves at all points have met the minimum value of SNI 6989.5: 2009 (R ≥ 0.995). In addition, based on the results of the comparison of the levels of the separate calibration and standard additions, the values are different, but the results of the t-test result in t-count <t-table. This means that there is no significant difference between separate calibration methods and standard addition.

Forward modelling of Kepler-band variability due to faculae and spots

ABSTRACT Variability observed in photometric light curves of late-type stars (on time-scales longer than a day) is a dominant noise source in exoplanet surveys and results predominantly from surface manifestations of stellar magnetic activity, namely faculae and spots. The implementation of faculae in light-curve models is an open problem, with scaling typically based on spectra equivalent to hot stellar atmospheres or assuming a solar-derived facular contrast. We modelled rotational (single period) light curves of active G2, K0, M0, and M2 stars, with Sun-like surface distributions and realistic limb-dependent contrasts for faculae and spots. The sensitivity of light-curve variability to changes in model parameters such as stellar inclination, feature area coverage, spot temperature, facular region magnetic flux density, and active band latitudes is explored. For our light-curve modelling approach we used actress, a geometrically accurate model for stellar variability. actress generates two-sphere maps representing stellar surfaces and populates them with user-prescribed spot and facular region distributions. From this, light curves can be calculated at any inclination. Quiet star limb darkening and limb-dependent facular contrasts were derived from MURaM 3D magnetoconvection simulations using ATLAS9. 1D stellar atmosphere models were used for the spot contrasts. We applied actress in Monte Carlo simulations, calculating light-curve variability amplitudes in the Kepler band. We found that, for a given spectral type and stellar inclination, spot temperature and spot area coverage have the largest effect on variability of all simulation parameters. For a spot coverage of $1{{\ \rm per\ cent}}$, the typical variability of a solar-type star is around 2 parts per thousand. The presence of faculae clearly affects the mean brightness and light-curve shape, but has relatively little influence on the variability.

Enhancing Properties of Soft Magnetic Materials: A Study into Hot Isostatic Pressing and Sintering Atmosphere Influences

Soft magnetic materials are characterized by achieving a high magnetic induction value in the presence of a small magnetic field. Common applications of these materials, such as transformers or sensors, are in constant evolution and new requirements are becoming more demanding. Nickel and its alloys are employed as smart materials taking advantage of their superior magnetoelastic properties. A metal injection molding (MIM) technique provides high-quality complex-shaped parts with a good density and controlled impurity levels, which are necessary for these applications, by carefully adjusting the sintering stage. Previous investigations have established a sintering cycle for pure nickel consisting of 1325 ∘C for 12 h within an N2-5%H2 atmosphere. Nevertheless, microstructural, mechanical and magnetoelastic responses can still be greatly enhanced. In this context, the effects of hot isostatic pressing (HIP), and sintering atmosphere have been investigated. The application of an adequate HIP treatment leads to significant improvements in comparison to the reference sintering process. It achieves almost complete densification while increasing field-dependent elastic modulus from 8.1% up to 9.6%. Additionally, the sintering atmosphere has been proven to be a key factor in reducing impurities and hence facilitating magnetic domain motion. Three different atmospheres have been studied: N2-5%H2 (with a higher gas flow), N2-10%H2-0.1%CH4 and low vacuum. Minimum carbon contents have been registered using more reducing atmospheres (N2-5%H2 and N2-10%H2-0.1%CH4) which has led to values of field-dependent elastic modulus higher than 10%. This value is 2.5 times higher than that obtained when nickel parts are processed via conventional techniques. Moreover, although minimizing carbon content has been shown to be easier and more beneficial than achieving complete densification, both strategies could be used in combination to improve and maximize magnetoelastic performance.

Stark broadening of spectral lines for zirconium ions Zr iv−vi in hot white dwarf atmospheres

ABSTRACT Stark widths for 31 spectral lines of the zirconium ions Zr iv, Zr v and Zr vi are calculated using a quantum mechanical method, and for five other lines they are deduced from a linear fit. Among these lines, 23 are provided for the first time. The motivation for this work was the recent identification of 25 lines of zirconium ions in the UV spectrum of the hot white dwarf RE 0503−289, which have never been detected before in hot white dwarfs. The results are presented for the plasma conditions found in hot white dwarf atmospheres. To the best of our knowledge, Stark broadening calculations have only been carried out for the Zr iv ion. Therefore, in addition to the quantum calculations, we perform semiclassical perturbation calculations for Zr iv lines and compare them with previous results, taking into account the effects of strong and elastic collisions on Stark broadening. Furthermore, we compare the Stark broadening with the Doppler broadening in order to ascertain their relative importance in the atmospheric conditions of DO white dwarfs. These results, together with atomic radiative data, are useful for non-local thermodynamic equilibrium stellar-atmosphere modelling.

Five carbon- and nitrogen-bearing species in a hot giant planet's atmosphere.

The atmospheres of gaseous giant exoplanets orbiting close to their parent stars (hot Jupiters) have been probed for nearly two decades1,2. They allow us to investigate the chemical and physical properties of planetary atmospheres under extreme irradiation conditions3. Previous observations of hot Jupiters as they transit in front of their host stars have revealed the frequent presence of water vapour4 and carbon monoxide5 in their atmospheres; this has been studied in terms of scaled solar composition6 under the usual assumption of chemical equilibrium. Both molecules as well as hydrogen cyanide were found in the atmosphere of HD209458b5,7,8, a well studied hot Jupiter (with equilibrium temperature around 1,500 kelvin), whereas ammonia was tentatively detected there9 and subsequently refuted10. Here we report observations of HD209458b that indicate the presence of water (H2O), carbon monoxide (CO), hydrogen cyanide (HCN), methane (CH4), ammonia (NH3) and acetylene (C2H2), with statistical significance of 5.3 to 9.9 standard deviations per molecule. Atmospheric models in radiative and chemical equilibrium that account for the detected species indicate a carbon-rich chemistry with a carbon-to-oxygen ratio close to or greater than 1, higher than the solar value (0.55). According to existing models relating the atmospheric chemistry to planet formation and migration scenarios3,11,12, this would suggest that HD209458b formed far from its present location and subsequently migrated inwards11,13. Other hot Jupiters may also show a richer chemistry than has been previously found, which would bring into question the frequently made assumption that they have solar-like and oxygen-rich compositions.