Using 2D thermal structure models and pseudo-2D chemical kinetics models, we explore how atmospheric temperatures and composition change as a function of altitude and longitude within the equatorial regions of close-in transiting Neptune-class exoplanets at different distances from their host stars. Our models predict that the day-night stratospheric temperature contrasts increase with increasing planetary effective temperatures T_eff; atmospheric composition also changes significantly with T_eff. Horizontal transport-induced quenching is very effective in our simulated exo-Neptune atmospheres, acting to homogenize the vertical profiles of species abundances with longitude at stratospheric pressures where infrared observations are sensitive. Our models have important implications for planetary emission observations as a function of orbital phase with the Ariel mission. Cooler solar-composition exo-Neptunes with T_eff = 500-700 K are predicted to have small variations in infrared emission spectra with orbital phase, making them less robust phase-curve targets for Ariel. Hot solar-composition exo-Neptunes with T_eff > 1300 K exhibit strong variations in infrared emission with orbital phase but are arguably less interesting from an atmospheric chemistry standpoint, with spectral signatures being dominated by a small number of species whose abundances are expected to be constant with longitude and consistent with thermochemical equilibrium. Solar-composition exo-Neptunes with T_eff = 900-1100 K reside in an interesting intermediate regime, with infrared phase curve variations being affected by both temperature and composition variations. This interesting intermediate regime shifts to smaller temperatures as atmospheric metallicity is increased, making cool higher-metallicity Neptune-class planets appropriate targets for Ariel phase-curve observations.
Since the discovery of the first extrasolar planet more than twenty years ago, we have discovered nearly four thousand planets orbiting stars other than the Sun. Current observational instruments (on board the Hubble Space Telescope, Spitzer, and on ground-based facilities) have allowed the scientific community to obtain important information on the physical and chemical properties of these planets. However, for a more in-depth characterisation of these worlds, more powerful telescopes are needed. Thanks to the high sensitivity of their instruments, the next generation of space observatories (…
Launching in 2028, ESA's Atmospheric Remote-sensing Exoplanet Large-survey (ARIEL) survey of $\sim$1000 transiting exoplanets will build on the legacies of Kepler and TESS and complement JWST by placing its high precision exoplanet observations into a large, statistically-significant planetary population context. With continuous 0.5--7.8~$μ$m coverage from both FGS (0.50--0.55, 0.8--1.0, and 1.0--1.2~$μ$m photometry; 1.25--1.95~$μ$m spectroscopy) and AIRS (1.95--7.80~$μ$m spectroscopy), ARIEL will determine atmospheric compositions and probe planetary formation histories during its 3.5-year mi…
The ESA-Ariel mission will include a tier dedicated to exoplanet phase curves corresponding to ~10% of the science time. We present here the current observing strategy for studying exoplanet phase curves with Ariel. We define science questions, requirements and a list of potential targets. We also estimate the precision of phase curve reconstruction and atmospheric retrieval using simulated phase curves. Based on this work, we found that full-orbit phase variations for 35-40 exoplanets could be observed during the 3.5-yr mission. This statistical sample would provide key constraints on atmosph…
On the synergetic use of Ariel and JWST for exoplanet atmospheric science
Kapteyn Institute University of Groningen（格罗宁根大学卡普坦研究所）；Université Paris-Saclay Université Paris Cité CEA CNRS AIM（巴黎萨克雷大学 巴黎西岱大学 CEA CNRS AIM）；King’s College London（伦敦国王学院）；LIRA Observatoire de Paris Université PSL CNRS Sorbonne Université Univ. Paris Cité Sorbonne Paris Cité（巴黎天文台 PSL大学 CNRS 索邦大学 巴黎西岱大学）；Department of Physics McGill University（麦吉尔大学物理系）；Department of Earth & Planetary Sciences McGill University（麦吉尔大学地球与行星科学系）；University of Valencia（瓦伦西亚大学）；INAF Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所阿切特里天文台）；Space Telescope Science Institute（太空望远镜科学研究所）；SRON Space Research Organisation Netherlands（荷兰空间研究组织）；Astrobiology Center（天体生物学中心）；National Astronomical Observatory of Japan（日本国立天文台）
Stellar flares with Ariel: detection prospects and impacts on exoplanet spectroscopy
Konkoly Observatory（孔科利天文台）；HUN-REN Research Centre for Astronomy and Earth Sciences（匈牙利研究网络地球与天文学研究中心）；HUN-REN CSFK MTA Centre of Excellence（匈牙利研究网络 CSFK 马塔科学院卓越中心）；SRON Space Research Organisation Netherlands（荷兰空间研究组织 SRON）
The recently adopted Ariel ESA mission will measure the atmospheric composition of a large number of exoplanets. This information will then be used to better constrain planetary bulk compositions. While the connection between the composition of a planetary atmosphere and the bulk interior is still being investigated, the combination of the atmospheric composition with the measured mass and radius of exoplanets will push the field of exoplanet characterisation to the next level, and provide new insights of the nature of planets in our galaxy. In this white paper, we outline the ongoing activiti…
Since the first discovery of an extra-solar planet around a main-sequence star, in 1995, the number of detected exoplanets has increased enormously. Over the past two decades, observational instruments (both onboard and on ground-based facilities) have revealed an astonishing diversity in planetary physical features (i. e. mass and radius), and orbital parameters (e.g. period, semi-major axis, inclination). Exoplanetary atmospheres provide direct clues to understand the origin of these differences through their observable spectral imprints. In the near future, upcoming ground and space-based t…
The Transit Timing Variation (TTV) technique is a powerful dynamical tool to measure exoplanetary masses by analysing transit light curves. We assessed the transit timing performances of the Ariel Fine Guidance Sensors (FGS1/2) based on the simulated light curve of a bright, 55 Cnc, and faint, K2-24, planet-hosting star. We estimated through a Markov-Chain Monte-Carlo analysis the transit time uncertainty at the nominal cadence of 1 second and, as a comparison, at a 30 and 60-s cadence. We found that at the nominal cadence Ariel will be able to measure the transit time with a precision of abou…
Machine Learning and Deep Learning for Exoplanet Detection and Atmospheric Characterization with JWST and the Upcoming Ariel Mission
Department of Industrial Physics, Enugu State University of Science and Technology（恩古州科技大学工业物理系）；Department of Physics, Dennis Osadebay University（德尼斯·奥萨德贝大学物理系）
Probing Exoplanetary Chemistry with Ariel: Scientific Priorities and Observational Strategies
Univ. Grenoble Alpes CNRS IPAG（格勒诺布尔阿尔卑斯大学法国国家科学研究中心IPAG实验室）；Université Paris Cité and Univ Paris Est Creteil CNRS LISA（巴黎西岱大学和巴黎东 Créteil大学法国国家科学研究中心LISA实验室）；SRON Netherlands Institute for Space Research（荷兰空间研究所）；Leiden Observatory Leiden University（莱顿大学莱顿天文台）；Anton Pannekoek Institute for Astronomy University of Amsterdam（阿姆斯特丹大学安东·潘内克天文学研究所）；IRAP Université de Toulouse CNRS/UMR 5277 UPS-OMP（图卢兹大学法国国家科学研究中心IRAP研究所）；Institute（研究所）
This is an exciting era for exo-planetary exploration. The recently launched JWST, and other upcoming space missions such as Ariel, Twinkle and ELTs are set to bring fresh insights to the convoluted processes of planetary formation and evolution and its connections to atmospheric compositions. However, with new opportunities come new challenges. The field of exoplanet atmospheres is already struggling with the incoming volume and quality of data, and machine learning (ML) techniques lands itself as a promising alternative. Developing techniques of this kind is an inter-disciplinary task, one t…
The Ariel mission will observe spectroscopically around 1000 exoplanets to further characterise their atmospheres. For the mission to be as efficient as possible, a good knowledge of the planets' ephemerides is needed before its launch in 2028. While ephemerides for some planets are being refined on a per-case basis, an organised effort to collectively verify or update them when necessary does not exist. In this study, we introduce the ExoClock project, an open, integrated and interactive platform with the purpose of producing a confirmed list of ephemerides for the planets that will be observ…
Identifying deformed exoplanets with JWST and Ariel: A target selection metric for phase curve observations
Leiden University（莱顿大学）；SRON, Space Research Organisation Netherlands（荷兰空间研究组织）；Observatoire astronomique de l’Université de Genève（日内瓦大学天文台）；University of New South Wales（新南威尔士大学）；Universidad de Antioquia（安蒂奥基亚大学）
Simulation-based Inference for Exoplanet Atmospheric Retrieval: Insights from winning the Ariel Data Challenge 2023 using Normalizing Flows
AstroAI；Ecole Polytechnique（巴黎综合理工学院）；Institute of Theory and Computation（理论与计算研究所）；Massachusetts Institute of Technology（麻省理工学院）；University of Southampton（南安普顿大学）；Kavli Institute for Astrophysics and Space Research（卡弗里天体物理与空间研究所）
The study of extrasolar planets and of the Solar System provides complementary pieces of the mosaic represented by the process of planetary formation. Exoplanets are essential to fully grasp the huge diversity of outcomes that planetary formation and the subsequent evolution of the planetary systems can produce. The orbital and basic physical data we currently possess for the bulk of the exoplanetary population, however, do not provide enough information to break the intrinsic degeneracy of their histories, as different evolutionary tracks can result in the same final configurations. The lesso…
To investigate the feasibility of ancillary target observations with ESA's Ariel mission, we compiled a list of potentially interesting young stars: FUors, systems harbouring extreme debris discs and a larger sample of young stellar objects showing strong near/mid-infrared excess. These objects can be observed as additional targets in the waiting times between the scheduled exoplanet transit and occultation observations. After analyzing the schedule for Ariel an algorithm was constructed to find the optimal target to be observed in each gap. The selection was mainly based on the slew and stabi…
The Ariel mission will characterise the chemical and thermal properties of the atmospheres of about a thousand exoplanets transiting their host star(s). The observation of such a large sample of planets will allow to deepen our understanding of planetary and atmospheric formation at the early stages, providing a truly representative picture of the chemical nature of exoplanets, and relating this directly to the type and chemical environment of the host star. Hence, the accurate and precise determination of the host star fundamental properties is essential to Ariel for drawing a comprehensive p…
Polycyclic aromatic hydrocarbons (PAHs) play a key role in the chemical and hydrodynamical evolution of the atmospheres of exoplanets and planet-forming discs. If they can survive the planet formation process, PAHs are likely to be involved in pre-biotic chemical reactions eventually leading to more complex molecules such as amino acids and nucleotides, which form the basis for life as we know it. However, the abundance and specific role of PAHs in these environments is largely unknown due to limitations in sensitivity and range of wavelength of current and previous space-borne facilities. Upc…
On the Information Content of Ariel Transmission Spectra: Reassessing the Tier System
University of Chicago（芝加哥大学）；Institut Trottier de Recherche sur les Exoplanètes（特罗蒂尔系外行星研究所）；McGill University（麦吉尔大学）；McMaster University（麦克马斯特大学）；Cornell University（康奈尔大学）
The ExoClock project is an inclusive, integrated, and interactive platform that was developed to monitor the ephemerides of the Ariel targets to increase the mission efficiency. The project makes the best use of all available resources, i.e., observations from ground telescopes, mid-time values from the literature and finally, observations from space instruments. Currently, the ExoClock network includes 280 participants with telescopes capable of observing 85\% of the currently known Ariel candidate targets. This work includes the results of $\sim$1600 observations obtained up to the 31st of D…
Thermal phase curves of exoplanet atmospheres have revealed temperature maps as a function of planetary longitude, often by sinusoidal decomposition of the phase curve. We construct a framework for describing two-dimensional temperature maps of exoplanets with mathematical basis functions derived for a fluid layer on a rotating, heated sphere with drag/friction, which are generalizations of spherical harmonics. These basis functions naturally produce physically-motivated temperature maps for exoplanets with few free parameters. We investigate best practices for applying this framework to tempe…
Observations of 43 complete transits of the hot Jupiter exoplanet HAT-P-32b using the MicroObservatory 0.15-m robotic telescope network covering a period of 7 years are presented. Compared with the most recent ephemeris for the system, the precision of the mid-transit times yielded a root-mean-square value from the predicted model of 3.0 min. The estimated system parameters based on EXOFAST modelling are broadly consistent with those of the default parameter values listed in the NASA Exoplanet Archive. An updated orbital period of 2.15000815 +/- 0.00000013 d and ephemeris of 2458881.71392 +/- …
University College London（伦敦大学学院）；European Space Agency, ESAC（欧洲空间局，欧洲空间天文中心）；King’s College London, University of London（伦敦国王学院，伦敦大学）；Université Paris Cité and Univ Paris Est Creteil, CNRS, LISA（巴黎西岱大学与巴黎东克雷泰伊大学，法国国家科学研究中心，天体物理和行星实验室）
We present a novel retrieval technique that attempts to model phase curve observations of exoplanets more realistically and reliably, which we call the 2.5-dimension (2.5-D) approach. In our 2.5-D approach we retrieve the vertical temperature profile and mean gaseous abundance of a planet at all longitudes and latitudes \textbf{simultaneously}, assuming that the temperature or composition, $x$, at a particular longitude and latitude $(Λ,Φ)$ is given by $x(Λ,Φ) = \bar{x} + (x(Λ,0) - \bar{x})\cos^nΦ$, where $\bar{x}$ is the mean of the morning and evening terminator values of $x(Λ,0)$, and $n$ i…
For terrestrial exoplanets with thin atmospheres or no atmospheres, the surface contributes light to the reflected light signal of the planet. Measurement of the variety of disk-integrated brightnesses of bodies in the Solar System and the variation with illumination and wavelength is essential for both planning imaging observations of directly imaged exoplanets and interpreting the eventual datasets. Here we measure the change in brightness of the Galilean satellites as a function of planetocentric longitude, illumination phase angle, and wavelength. The data span a range of wavelengths from …
Ariel, the Atmospheric Remote-sensing Infrared Exoplanet Large-survey, was adopted as the fourth medium-class mission in ESA's Cosmic Vision programme to be launched in 2029. During its 4-year mission, Ariel will study what exoplanets are made of, how they formed and how they evolve, by surveying a diverse sample of about 1000 extrasolar planets, simultaneously in visible and infrared wavelengths. It is the first mission dedicated to measuring the chemical composition and thermal structures of hundreds of transiting exoplanets, enabling planetary science far beyond the boundaries of the Solar …
Radiatively Controlled Thermal Stability of High-Altitude Clouds in Exoplanetary Atmospheres
Meikei Gakuen High School（明海学园高等学校）；Division of Science, National Astronomical Observatory of Japan（日本国立天文台科学部）；Graduate Institute for Advanced Studies, SOKENDAI（SOKENDAI高等研究院）
In the recent years, retrieval analysis of exoplanet atmospheres have been very successful, providing deep insights on the composition and the temperature structure of these worlds via the transit and eclipse methods. Analysis of spectral phase curve observations, which in theory provides even more information, are still limited to a few planets. In the next decade, new facilities such as NASA-JWST and ESA-Ariel will revolutionise the field of exoplanet atmospheres and we expect that a significant time will be spent on spectral phase curve observations. Most current models are still limited in…
The GAPS Programme at TNG. LXXIII. Confirmation of the hot sub-Neptune TOI-4602 b (HD 25295 b), a key target for future atmospheric characterization
INAF – Osservatorio Astronomico di Palermo（意大利国家天体物理研究所巴勒莫天文台）；ESO - European Southern Observatory（欧洲南方天文台）；INAF-Osservatorio Astronomico di Roma（意大利国家天体物理研究所罗马天文台）；INAF – Osservatorio Astrofisico di Catania（意大利国家天体物理研究所卡塔尼亚天文台）；Institute for Particle Physics and Astrophysics, ETH Zürich（苏黎世联邦理工学院粒子物理与天体物理研究所）；Space Research Institute, Austrian Academy of Sciences（奥地利科学院空间研究所）
Aims. To create a retrieval framework which encapsulates the 3D nature of exoplanet atmospheres, and to apply it to observed emission phase curve and transmission spectra of hot Jupiter exoplanet WASP-43b. Methods. We present our 3D framework, which is freely available as a stand-alone module from GitHub. We use the atmospheric modelling and Bayesian retrieval package ARCiS (ARtful modelling Code for exoplanet Science) to perform 8 3D retrievals on simultaneous transmission (HST/WFC3) and phase-dependent emission (HST/WFC3, Spitzer/IRAC) observations of WASP-43b as a case study. We assess how …
Observations of time-resolved thermal emission from tidally locked exoplanets can tell us about their atmospheric temperature structure. Telescopes such as JWST and ARIEL will improve the quality and availability of these measurements. This motivates an improved understanding of the processes that determine atmospheric temperature structure, particularly atmospheric circulation. The circulation is important in determining atmospheric temperatures, not only through its ability to transport heat, but also because any circulation pattern needs to be balanced by horizontal pressure contrasts, ther…
The ExoClock project has been created with the aim of increasing the efficiency of the Ariel mission. It will achieve this by continuously monitoring and updating the ephemerides of Ariel candidates over an extended period, in order to produce a consistent catalogue of reliable and precise ephemerides. This work presents a homogenous catalogue of updated ephemerides for 450 planets, generated by the integration of $\sim$18000 data points from multiple sources. These sources include observations from ground-based telescopes (ExoClock network and ETD), mid-time values from the literature and lig…
The raw exospheric composition data of Mars for the period September 2014 to October 2015 has been retrieved and analysed using the observations carried out by Mars Exospheric Neutral Composition Analyser (MENCA) payload on-board the Mars Orbiter Mission (MOM) launched by India on 5 November 2013. The state parameters viz. latitude, longitude, altitude and solar zenith angle coverage of the partial pressures of different exospheric constituents are determined and assigned to enrich the usefulness of data with orbit-wise assimilation particularly between 250 and 500 km altitude range of main in…
Accelerating exoplanet climate modelling: A machine learning approach to complement 3D GCM grid simulations
Space Research Institute, Austrian Academy of Sciences（空间研究所，奥地利科学院）；Institute for Theoretical Physics and Computational Physics, Graz University of Technology（理论物理与计算物理研究所，格拉茨技术大学）；Institute of Physics, University of Graz（物理研究所，格拉茨大学）
The first opportunity to detect indications for life outside the Solar System may be provided already within the next decade with upcoming missions such as the James Webb Space Telescope (JWST), the European Extremely Large Telescope (E-ELT) and/or the Atmospheric Remote-sensing Infrared Exoplanet Large-survey (ARIEL) mission, searching for atmospheric biosignatures on planets in the habitable zone of cool K- and M-stars. Nevertheless, their harsh stellar radiation and particle environment could lead to photochemical loss of atmospheric biosignatures. We aim to study the influence of cosmic ra…
The EXoplanet Climate Infrared TElescope (EXCITE): A balloon-borne mission to measure spectroscopic phase curves of transiting hot Jupiters
NASA Goddard Space Flight Center（美国宇航局戈达德太空飞行中心）；Brown University（布朗大学）；Arizona State University（亚利桑那州立大学）；La Sapienza Università di Roma（罗马第一大学）；Cornell University（康奈尔大学）；StarSpec Technologies Inc.（StarSpec科技有限公司）；Center for Space Sciences and Technology, University of Maryland, Baltimore County（马里兰大学巴尔的摩县分校空间科学与技术中心）
