Single-crystalline, wormlike hematite photoanodes for efficient solar water splitting

A hematite photoanode showing a stable, record-breaking performance of 4.32 mA/cm(2) photoelectrochemical water oxidation current at 1.23 V vs. RHE under simulated 1-sun (100 mW/cm(2)) irradiation is reported. This photocurrent corresponds to ca. 34% of the maximum theoretical limit expected for hematite with a band gap of 2.1 V. The photoanode produced stoichiometric hydrogen and oxygen gases in amounts close to the expected values from the photocurrent. The hematitle has a unique single-crystalline "wormlike" morphology produced by in-situ two-step annealing at 550 degrees C and 800 degrees C of beta-FeOOH nanorods grown directly on a transparent conducting oxide glass via an all-solution method. In addition, it is modified by platinum doping to improve the charge transfer characteristics of hematite and an oxygen-evolving co-catalyst on the surface.open2

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

The PLATO 2.0 mission

PLATO 2.0 has recently been selected for ESA's M3 launch opportunity (2022/24). Providing accurate key planet parameters (radius, mass, density and age) in statistical numbers, it addresses fundamental questions such as: How do planetary systems form and evolve? Are there other systems with planets like ours, including potentially habitable planets? The PLATO 2.0 instrument consists of 34 small aperture telescopes (32 with 25 s readout cadence and 2 with 2.5 s candence) providing a wide field-of-view (2232 deg 2) and a large photometric magnitude range (4-16 mag). It focusses on bright (4-11 mag) stars in wide fields to detect and characterize planets down to Earth-size by photometric transits, whose masses can then be determined by ground-based radial-velocity follow-up measurements. Asteroseismology will be performed for these bright stars to obtain highly accurate stellar parameters, including masses and ages. The combination of bright targets and asteroseismology results in high accuracy for the bulk planet parameters: 2 %, 4-10 % and 10 % for planet radii, masses and ages, respectively. The planned baseline observing strategy includes two long pointings (2-3 years) to detect and bulk characterize planets reaching into the habitable zone (HZ) of solar-like stars and an additional step-and-stare phase to cover in total about 50 % of the sky. PLATO 2.0 will observe up to 1,000,000 stars and detect and characterize hundreds of small planets, and thousands of planets in the Neptune to gas giant regime out to the HZ. It will therefore provide the first large-scale catalogue of bulk characterized planets with accurate radii, masses, mean densities and ages. This catalogue will include terrestrial planets at intermediate orbital distances, where surface temperatures are moderate. Coverage of this parameter range with statistical numbers of bulk characterized planets is unique to PLATO 2.0. The PLATO 2.0 catalogue allows us to e.g.: - complete our knowledge of planet diversity for low-mass objects, - correlate the planet mean density-orbital distance distribution with predictions from planet formation theories,- constrain the influence of planet migration and scattering on the architecture of multiple systems, and - specify how planet and system parameters change with host star characteristics, such as type, metallicity and age. The catalogue will allow us to study planets and planetary systems at different evolutionary phases. It will further provide a census for small, low-mass planets. This will serve to identify objects which retained their primordial hydrogen atmosphere and in general the typical characteristics of planets in such low-mass, low-density range. Planets detected by PLATO 2.0 will orbit bright stars and many of them will be targets for future atmosphere spectroscopy exploring their atmosphere. Furthermore, the mission has the potential to detect exomoons, planetary rings, binary and Trojan planets. The planetary science possible with PLATO 2.0 is complemented by its impact on stellar and galactic science via asteroseismology as well as light curves of all kinds of variable stars, together with observations of stellar clusters of different ages. This will allow us to improve stellar models and study stellar activity. A large number of well-known ages from red giant stars will probe the structure and evolution of our Galaxy. Asteroseismic ages of bright stars for different phases of stellar evolution allow calibrating stellar age-rotation relationships. Together with the results of ESA's Gaia mission, the results of PLATO 2.0 will provide a huge legacy to planetary, stellar and galactic science

4MOST: 4-metre Multi-Object Spectroscopic Telescope

1134MOST is a wide-field, high-multiplex spectroscopic survey facility under development for the VISTA telescope of the European Southern Observatory (ESO). Its main science drivers are in the fields of galactic archeology, high-energy physics, galaxy evolution and cosmology. 4MOST will in particular provide the spectroscopic complements to the large area surveys coming from space missions like Gaia, eROSITA, Euclid, and PLATO and from ground-based facilities like VISTA, VST, DES, LSST and SKA. The 4MOST baseline concept features a 2.5 degree diameter field-of-view with ~2400 fibres in the focal surface that are configured by a fibre positioner based on the tilting spine principle. The fibres feed two types of spectrographs; ~1600 fibres go to two spectrographs with resolution R<5000 (λ~390-930 nm) and ~800 fibres to a spectrograph with R>18,000 (λ~392-437 nm and 515-572 nm and 605-675 nm). Both types of spectrographs are fixed-configuration, three-channel spectrographs. 4MOST will have an unique operations concept in which 5 year public surveys from both the consortium and the ESO community will be combined and observed in parallel during each exposure, resulting in more than 25 million spectra of targets spread over a large fraction of the southern sky. The 4MOST Facility Simulator (4FS) was developed to demonstrate the feasibility of this observing concept. 4MOST has been accepted for implementation by ESO with operations expected to start by the end of 2020. This paper provides a top-level overview of the 4MOST facility, while other papers in these proceedings provide more detailed descriptions of the instrument concept[1], the instrument requirements development[2], the systems engineering implementation[3], the instrument model[4], the fibre positioner concepts[5], the fibre feed[6], and the spectrographs[7].nonenonede Jong Roelof S.; Barden Sam; Bellido-Tirado Olga; Brynnel Joar; Chiappini Cristina; Depagne Éric; Haynes Roger; Johl Diana; Phillips Daniel P.; Schnurr Olivier; Schwope Axel D.; Walcher Jakob; Bauer Svend M.; Cescutti G; Cioni Maria-Rosa L.; Dionies Frank; Enke Harry; Haynes Dionne M.; Kelz Andreas; Kitaura Francisco S.; Lamer Georg; Minchev Ivan; Müller Volker; Nuza Sebastián. E.; Olaya Jean-Christophe; Piffl Tilmann; Popow Emil; Saviauk Allar; Steinmetz Matthias; Ural Uǧur; Valentini Monica; Winkler Roland; Wisotzki Lutz; Ansorge Wolfgang R.; Banerji Manda; Gonzalez Solares Eduardo; Irwin Mike; Kennicutt Robert C.; King David M. P.; McMahon Richard; Koposov Sergey; Parry Ian R.; Sun Xiaowei; Walton Nicholas A.; Finger Gert; Iwert Olaf; Krumpe Mirko; Lizon Jean-Louis; Mainieri Vincenzo; Amans Jean-Philippe; Bonifacio Piercarlo; Cohen Matthieu; François Patrick; Jagourel Pascal; Mignot Shan B.; Royer Frédéric; Sartoretti Paola; Bender Ralf; Hess Hans-Joachim; Lang-Bardl Florian; Muschielok Bernard; Schlichter Jörg; Böhringer Hans; Boller Thomas; Bongiorno Angela; Brusa Marcella; Dwelly Tom; Merloni Andrea; Nandra Kirpal; Salvato Mara; Pragt Johannes H.; Navarro Ramón; Gerlofsma Gerrit; Roelfsema Ronald; Dalton Gavin B.; Middleton Kevin F.; Tosh Ian A.; Boeche Corrado; Caffau Elisabetta; Christlieb Norbert; Grebel Eva K.; Hansen Camilla J.; Koch Andreas; Ludwig Hans-G.; Mandel Holger; Quirrenbach Andreas; Sbordone Luca; Seifert Walter; Thimm Guido; Helmi Amina; trager Scott C.; Bensby Thomas; Feltzing Sofia; Ruchti Gregory; Edvardsson Bengt; Korn Andreas; Lind Karin; Boland Wilfried; Colless Matthew; Frost Gabriella; Gilbert James; Gillingham Peter; Lawrence Jon; Legg Neville; Saunders Will; Sheinis Andrew; Driver Simon; Robotham Aaron; Bacon Roland; Caillier Patrick; Kosmalski Johan; Laurent Florence; Richard Johande Jong Roelof, S.; Barden, Sam; Bellido-Tirado, Olga; Brynnel, Joar; Chiappini, Cristina; Depagne, Éric; Haynes, Roger; Johl, Diana; Phillips Daniel, P.; Schnurr, Olivier; Schwope Axel, D.; Walcher, Jakob; Bauer Svend, M.; Cescutti, G; Cioni Maria-Rosa, L.; Dionies, Frank; Enke, Harry; Haynes Dionne, M.; Kelz, Andreas; Kitaura Francisco, S.; Lamer, Georg; Minchev, Ivan; Müller, Volker; Nuza, Sebastián. E.; Olaya, Jean-Christophe; Piffl, Tilmann; Popow, Emil; Saviauk, Allar; Steinmetz, Matthias; Ural, Uǧur; Valentini, Monica; Winkler, Roland; Wisotzki, Lutz; Ansorge Wolfgang, R.; Banerji, Manda; Gonzalez Solares, Eduardo; Irwin, Mike; Kennicutt Robert, C.; King David, M. P.; Mcmahon, Richard; Koposov, Sergey; Parry Ian, R.; Sun, Xiaowei; Walton Nicholas, A.; Finger, Gert; Iwert, Olaf; Krumpe, Mirko; Lizon, Jean-Louis; Mainieri, Vincenzo; Amans, Jean-Philippe; Bonifacio, Piercarlo; Cohen, Matthieu; François, Patrick; Jagourel, Pascal; Mignot Shan, B.; Royer, Frédéric; Sartoretti, Paola; Bender, Ralf; Hess, Hans-Joachim; Lang-Bardl, Florian; Muschielok, Bernard; Schlichter, Jörg; Böhringer, Hans; Boller, Thomas; Bongiorno, Angela; Brusa, Marcella; Dwelly, Tom; Merloni, Andrea; Nandra, Kirpal; Salvato, Mara; Pragt Johannes, H.; Navarro, Ramón; Gerlofsma, Gerrit; Roelfsema, Ronald; Dalton Gavin, B.; Middleton Kevin, F.; Tosh Ian, A.; Boeche, Corrado; Caffau, Elisabetta; Christlieb, Norbert; Grebel Eva, K.; Hansen Camilla, J.; Koch, Andreas; Ludwig, Hans-G.; Mandel, Holger; Quirrenbach, Andreas; Sbordone, Luca; Seifert, Walter; Thimm, Guido; Helmi, Amina; trager Scott, C.; Bensby, Thomas; Feltzing, Sofia; Ruchti, Gregory; Edvardsson, Bengt; Korn, Andreas; Lind, Karin; Boland, Wilfried; Colless, Matthew; Frost, Gabriella; Gilbert, James; Gillingham, Peter; Lawrence, Jon; Legg, Neville; Saunders, Will; Sheinis, Andrew; Driver, Simon; Robotham, Aaron; Bacon, Roland; Caillier, Patrick; Kosmalski, Johan; Laurent, Florence; Richard, Joha