Extremely Large Telescopes Research Articles

First on-sky results of a Fabry–Perot Instrument for Oxygen Searches (FIOS) prototype

Context. The upcoming Extremely Large Telescopes (ELTs) are expected to have a sufficient collecting area required to detect potential biosignature gases such as molecular oxygen, O2, in the atmosphere of terrestrial planets around nearby stars. Aims. One of the most promising detection methods is transmission spectroscopy. To maximize our capability to detect O2 using this method, spectral resolutions R ≥ 300 000 are required to fully resolve the absorption lines in an Earth-like exoplanet atmosphere and disentangle the signal from telluric lines. Methods. Current high-resolution spectrographs typically achieve a spectral resolution of R ~ 100 000. Increasing the resolution in seeing limited observations and/or instruments requires drastically larger optical components, making these instruments even more expensive and hard to fabricate and assemble. Instead, we demonstrate a new approach to high-resolution spectroscopy. We implemented an ultra-high spectral resolution booster to be coupled to a high-resolution spectrograph. The instrument is based on a chained Fabry-Perot array which generates a hyperfine spectral profile. Results. We present on-sky telluric observations with a lab demonstrator. Depending on the configuration, this two-arm prototype reaches a resolution of R = 250 000–350 000. After carefully modeling the prototype’s behavior, we propose a Fabry-Perot Interferometer (FPI) design for an eight-arm array configuration aimed at ELTs capable of exceeding R = 300 000. Conclusions. The novel FPI resolution booster can be plugged in at the front end of an existing R = 100 000 spectrograph to overwrite the spectral profile with a higher resolution for exoplanet atmosphere studies.

Detector system challenges of the wide‐field spectroscopic survey telescope (WST)

AbstractThe wide‐field spectroscopic survey telescope (WST) is proposed to become the next large optical/near infrared facility for the European southern observatory (ESO) once the extremely large telescope (ELT) has become operational. While the latter is optimized for unprecedented sensitivity and adaptive‐optics assisted image quality over a small field of view, WST addresses the need for large survey volumes in spectroscopy with the light‐collecting power of a 10‐m class telescope. Its unique layout will feature the combination of multi‐object and integral field spectroscopy simultaneously. For the intended capacity of this layout, a very large number of detectors are needed. The complexity of the detector systems presents a number of challenges that are discussed with a focus on novel approaches and innovative detector designs that can be expected to emerge over the anticipated 20‐year timeline of this project.

TAU: A neural network based telluric correction framework

Context. Telluric correction is one of the critically important outstanding issues for extreme precision radial velocities and exoplanet atmosphere observations. Thorough removal of small so-called micro tellurics across the entire wavelength range of optical spectro-graphs is necessary in order to reach the extreme radial velocity precision required to detect Earth-analog exoplanets orbiting in the habitable zone of solar-type stars. Likewise, proper treatment of telluric absorption will be important for exoplanetary atmosphere observations with high-resolution spectrographs on future extremely large telescopes (ELTs). Aims. In this work, we introduce the Telluric AUtoencoder (TAU). TAU is an accurate high-speed telluric correction framework built to extract the telluric spectrum with previously unobtained precision in a computationally efficient manner. Methods. TAU is built on a neural network autoencoder trained to extract a highly detailed telluric transmission spectrum from a large set of high-precision observed solar spectra. We accomplished this by reducing the data into a compressed representation, allowing us to unveil the underlying solar spectrum and simultaneously uncover the different modes of variation in the observed spectra relating to the absorption from H2O and O2 in the atmosphere of Earth. Results. We demonstrate the approach on data from the HARPS-N spectrograph and show how the extracted components can be scaled to remove H2O and O2 telluric contamination with improved accuracy and at a significantly lower computational expense than the current state of the art synthetic approach molecfit. We also demonstrate the capabilities of TAU to remove telluric contamination from observations of the ultra-hot Jupiter HAT-P-70b allowing for the retrieval of the atmospheric signal. We publish the extracted components and an open-source code base allowing scholars to apply TAU on their own data.

Off-axis point spread function reconstruction forsingle conjugate adaptive optics.

Modern giant segmented mirror telescopes (GSMTs) such as the Extremely Large Telescope, which is currently under construction, depend heavily on adaptive optics (AO) systems to correct for atmospheric distortions. However, a residual blur always remains in the astronomical images corrected by single conjugate AO (SCAO) systems due to fitting and bandwidth errors, which can mathematically be described by a convolution of the true image with a point spread function (PSF). Due to the nature of the turbulent atmosphere and its correction, the PSF is spatially varying, which is known as an anisoplanatic effect. The PSF serves, e.g.,as a quality measure for science images and therefore needs to be known as accurately as possible. In this paper, we present an algorithm for PSF reconstruction from pupil-plane data in directions apart from the guide star direction in an SCAO system. Our algorithm is adapted to the needs of GSMTs focused on estimating the contribution of the anisoplanatic and generalized fitting error to the PSF. Results obtained in an end-to-end simulation tool show a qualitatively good reconstruction of the PSF compared to the PSF calculated directly from the simulated incoming wavefront as well as stable performance with respect to imprecise knowledge of atmospheric parameters.

Spatially resolved mock observations of stellar kinematics: full radiative transfer treatment of simulated galaxies

ABSTRACT We present a framework to build realistic mock spectroscopic observations for state-of-the-art hydrodynamical simulations, using high spectral resolution stellar population models and full radiative transfer treatment with skirt. As a first application, we generate stellar continuum mock observations for the Auriga cosmological zoom simulations emulating integral-field observations from the Sydney–AOO Multi-object Integral Field Spectrograph (SAMI) Galaxy Survey. We perform spectral fitting on our synthetic cubes and compute the resulting rotation velocity (Vrot) and velocity dispersion within 1Re (σe) for a subset of the Auriga sample. We find that the kinematics produced by Auriga are in good agreement with the observations from the SAMI galaxy survey after taking into account the effects of dust and the systematics produced by the observation limitations. We also explore the effects of seeing convolution, inclination, and attenuation on the line-of-sight velocity distribution. For highly inclined galaxies, these effects can lead to an artificial decrease in the measured V/σ by nearly a factor of two (after inclination correction). We also demonstrate the utility of our method for high-redshift galaxies by emulating spatially resolved continuum spectra from the Large Early Galaxy Census (LEGA-C) survey and, looking forward, the European Extremely Large Telescope (E-ELT) High Angular Resolution Monolithic Optical and Near-infrared Integral field spectrograph (HARMONI). Our framework represents a crucial link between the ground truth for stellar populations and kinematics in simulations and the observed stellar continuum observations at low and high redshift.

On the effects of spider-arms vignetting on interferometric measurements of deformable mirrors

The interferometric calibration and measurement of deformable mirrors for adaptive optics are often performed on complex optical system with spider arms. The spider shadows may divide the mirror surface into separate islands on the detector, so the interferometer fails in reconnecting them to a common phase value. The calibration measurements then suffer from such artificial differential pistons across islands, which is converted into a wrong actuator command and in general into a poor calibration. We review the effects of spider arms shadowing as experienced during the optical calibration of large format adaptive mirrors, such as the Large Binocular Telescope and Very Large Telescope ones; we describe the procedures that we tested to cope with these issues and their effectiveness; and we present a laboratory assessment of the effect of such a shadowing with a dedicated test setup. Our work is part of a preparatory activity for the optical test of the European Extremely Large Telescope adaptive mirror M4.

Bioverse: A Comprehensive Assessment of the Capabilities of Extremely Large Telescopes to Probe Earth-like O2 Levels in Nearby Transiting Habitable-zone Exoplanets

Molecular oxygen is a strong indicator of life on Earth and may indicate biological processes on exoplanets too. Recent studies proposed that Earth-like O2 levels might be detectable on nearby exoplanets using high-resolution spectrographs on future extremely large telescopes (ELTs). However, these studies did not consider constraints like relative velocities, planet occurrence rates, and target observability. We expanded on past studies by creating a homogeneous catalog of 286,391 main-sequence stars within 120 pc using Gaia DR3 and used the Bioverse framework to simulate the likelihood of finding nearby transiting Earth analogs. We also simulated a survey of M dwarfs within 20 pc accounting for η ⊕ estimates, transit probabilities, relative velocities, and target observability to determine how long ELTs and theoretical 50–100 m ground-based telescopes need to observe to probe for Earth-like O2 levels with an R = 100,000 spectrograph. This would only be possible within 50 yr for up to ∼21% of nearby M-dwarf systems if a suitable transiting habitable-zone Earth analog was discovered, assuming signals from every observable partial transit from each ELT can be combined. If so, Earth-like O2 levels could be detectable on TRAPPIST-1 d–g within 16–55 yr, respectively, and about half that time with an R = 500,000 spectrograph. These results have important implications for whether ELTs can survey nearby habitable-zone Earth analogs for O2 via transmission spectroscopy. Our work provides the most comprehensive assessment to date of the ground-based capabilities to search for life beyond the solar system.

Electro‐optical performance of the large visible adaptive optics sensor module

AbstractIn order to achieve the best possible atmospheric corrections using its deformable mirrors, the Extremely Large Telescope (ELT) and its instruments will depend on several different wavefront sensor cameras as part of its adaptive optics systems. LISA, one of three wavefront sensor cameras that have been developed in‐house at ESO, will utilize a custom‐designed, large‐format CMOS detector developed by ESO and Teledyne‐e2v: the Large Visible adaptive optics Sensor Module, LVSM, an pixel sensor capable of operation at speeds in excess of 700 frames per second. We present the results of the electro‐optical characterization of this detector.

There’s More to Life than O2: Simulating the Detectability of a Range of Molecules for Ground-based, High-resolution Spectroscopy of Transiting Terrestrial Exoplanets

Within the next decade, atmospheric O2 on Earth-like M-dwarf planets may be accessible with visible–near-infrared (NIR), high-spectral-resolution, ground-based extremely large telescope (ELT) instruments. However, the prospects for using ELTs to detect environmental properties that provide context for O2 have not been thoroughly explored. Additional molecules may help indicate planetary habitability, rule out abiotically generated O2, or reveal alternative biosignatures. To understand the accessibility of environmental context using ELT spectra, we simulate high-resolution transit transmission spectra of previously generated evolved terrestrial atmospheres. We consider inhabited preindustrial and Archean Earth–like atmospheres, and lifeless worlds with abiotic O2 buildup from CO2 and H2O photolysis. All atmospheres are self-consistent with M2V–M8V dwarf host stars. Our simulations include explicit treatment of systematic and telluric effects to model high-resolution spectra for Giant Magellan Telescope (GMT), Thirty Meter Telescope (TMT), and European ELT (E-ELT) configurations for systems 5 and 12 pc from Earth. Using the cross-correlation technique, we determine the detectability of major species in these atmospheres: O2, O3, CH4, CO2, CO, H2O, and C2H6. Our results suggest that CH4 and CO2 are the most accessible molecules for terrestrial planets transiting a range of M-dwarf hosts using an E-ELT-, TMT-, or GMT-sized telescope, and that the O2 NIR and H2O 0.9 μm bands may also be accessible with more observation time. Although this technique still faces considerable challenges, the ELTs will provide access to the atmospheres of terrestrial planets transiting earlier-type M-dwarf hosts that may not be possible using JWST.

Infrared detectors for first generation extremely large telescope instruments and their characterization program

The detectors for the three first generation extremely large telescope (ELT) instruments MICADO (Multi‐AO Imaging Camera for Deep Observations), HARMONI (A High Angular Resolution Monolithic Optical and Near‐infrared Integral Field Spectrograph), and METIS (A Mid‐infrared ELT Imager and Spectrograph) cover from the optical to longwave infrared wavelengths. MICADO and HARMONI detector focal planes require 17 H4RG (Hawaii‐4RG) near‐infrared whilst the METIS focal planes consist of 5 SWIR (shortwave infrared) detectors and one longwave infrared detector. Procurement of the optical and SWIR detectors has been completed, whilst the H4RGs and long wavelength detectors are still in progress. A custom cryogenic facility for infrared array testing (FIAT) has been designed and developed at European Southern Observatory (ESO) over the last few years in order to characterize the infrared detectors for ELT and future Very Large Telescope instruments. FIAT is currently being commissioned in our labs with an H4RG engineering detector. FIAT will be used to characterize the science H4RG‐15 detectors for MICADO and HARMONI, the two first‐light instruments of the ELT while the existing Mosaic Test Facility (MTF) will be used for characterizing the SWIR detectors for METIS. This paper presents an overview of the detector systems for the three instruments, their engineering challenges, and the requirements for the detectors' performance and their characterization program. The paper will also describe a test setup for H4RG detectors including a new preamplifier design with options to operate the detector in different modes and it will also report on the test results from the engineering H4RG detector, as part of the commissioning of FIAT and discuss detector performance and related detector issues.

Polarized Signatures of a Habitable World: Comparing Models of an Exoplanet Earth with Visible and Near-infrared Earthshine Spectra

In the JWST, Extremely Large Telescopes, and LUVOIR era, we expect to characterize a number of potentially habitable Earth-like exoplanets. However, the characterization of these worlds depends crucially on the accuracy of theoretical models. Validating these models against observations of planets with known properties will be key for the future characterization of terrestrial exoplanets. Due to its sensitivity to the micro- and macro-physical properties of an atmosphere, polarimetry will be an important tool that, in tandem with traditional flux-only observations, will enhance the capabilities of characterizing Earth-like planets. In this paper we benchmark two different polarization-enabled radiative-transfer codes against each other and against unique linear spectropolarimetric observations of the earthshine that cover wavelengths from ∼0.4 to ∼2.3 μm. We find that while the results from the two codes generally agree with each other, there is a phase dependency between the compared models. Additionally, with our current assumptions, the models from both codes underestimate the level of polarization of the earthshine. We also report an interesting discrepancy between our models and the observed 1.27 μm O2 feature in the earthshine, and provide an analysis of potential methods for matching this feature. Our results suggest that only having access to the 1.27 μm O2 feature coupled with a lack of observations of the O2 A and B bands could result in a mischaracterization of an Earth-like atmosphere. Providing these assessments is vital to aid the community in the search for life beyond the solar system.

The Direct Mid-infrared Detectability of Habitable-zone Exoplanets around Nearby Stars

Giant planets within the habitable zones of the closest several stars can currently be imaged with ground-based telescopes. Within the next decade, the Extremely Large Telescopes (ELTs) will begin to image the habitable zones of a greater number of nearby stars with much higher sensitivity, potentially imaging exo-Earths around the closest stars. To determine the most promising candidates for observations over the next decade, we establish a theoretical framework for the direct detectability of Earth- to super-Jovian-mass exoplanets in the mid-infrared based on available atmospheric and evolutionary models. Of the 83 closest BAFGK-type stars, we select 37 FGK-type stars within 10 pc and 34 BA-type stars within 30 pc with reliable age constraints. We prioritize targets based on a parametric model of a planet’s effective temperature based on a star's luminosity, distance, and age, and on the planet’s orbital semimajor axis, radius, and albedo. We then predict the most likely planets to be detectable with current 8 m telescopes and with a 39 m ELT with up to 100 hr of observation per star. Putting this together, we recommend observation times needed for the detection of habitable-zone exoplanets spanning the range from very nearby temperate Earth-sized planets to more distant young giant planets. We then recommend ideal initial targets for current telescopes and the upcoming ELTs.

Unscreening of f(R) gravity near the galactic center black hole: Testability through pericenter shift below S0-2’s orbit

General Relativity (GR) has been tested extensively in the solar system and is being tested in the new environment of the Galactic Center (GC) black hole where the dimensionless gravitational potential ([Formula: see text]) is 100 times stronger than the one encountered in solar system. Therefore, the neighborhood of the GC black hole is a naive opportunity to test modified theories of gravity. In this work, effect of [Formula: see text] gravity near the black hole is studied. The difference of pericenter shift between GR and [Formula: see text] gravity is studied for compact orbits having semi-major axis equal to and below [Formula: see text] au (S0-2 like orbits). In a model-dependent approach, we choose [Formula: see text] (power law gravity) model which is cosmologically motivated and study the deviation in orbital pericenter shift for both zero spin and non-zero spin of the black hole. It is found that effect of [Formula: see text] gravity becomes prominent for compact orbits. In model-independent approach to [Formula: see text] gravity with the generic scalaron fields ([Formula: see text]), we extract the parameters of [Formula: see text] gravity from the current bounds on Parametrized Post-Newtonian (PPN) parameters ([Formula: see text]) near the GC black hole. The screening of [Formula: see text] gravity is also investigated for these bounds on PPN parameters. It has been found that sufficiently massive scalarons ([Formula: see text][Formula: see text]eV) are completely screened but light and intermediate mass scalarons ([Formula: see text][Formula: see text]eV and [Formula: see text][Formula: see text]eV) are unscreened towards S0-2 like orbits as well as in the orbit of the newly discovered short period star S4716 ([Formula: see text][Formula: see text]au). The possibility of detection of the [Formula: see text] gravity effects due to these unscreened scalarons is forecasted with existing and upcoming astrometric capabilities of Extremely Large Telescopes (ELTs).

Observing circumplanetary disks with METIS

Context. Gaining a full understanding of the planet and moon formation process calls for observations that probe the circumplanetary environment of accreting giant planets. The mid-infrared ELT imager and spectrograph (METIS) will provide a unique capability to detect warm-gas emission lines from circumplanetary disks. Aims. We aim to demonstrate the capability of the METIS instrument on the Extremely Large Telescope (ELT) to detect circumplanetary disks (CPDs) with fundamental v = 1−0 transitions of 12CO from 4.5 to 5 μm. Methods. We considered the case of the well-studied HD 100546 pre-transitional disk to inform our disk modeling approach. We used the radiation-thermochemical disk modeling code ProDiMo to produce synthetic spectral channel maps. The observational simulator SimMETIS was employed to produce realistic data products with the integral field spectroscopic (IFU) mode. Results. The detectability of the CPD depends strongly on the level of external irradiation and the physical extent of the disk, favoring massive (~10 MJ) planets and spatially extended disks, with radii approaching the planetary Hill radius. The majority of 12CO line emission originates from the outer disk surface and, thus, the CO line profiles are centrally peaked. The planetary luminosity does not contribute significantly to exciting disk gas line emission. If CPDs are dust-depleted, the 12CO line emission is enhanced as external radiation can penetrate deeper into the line emitting region. Conclusions. UV-bright star systems with pre-transitional disks are ideal candidates to search for CO-emitting CPDs with ELT/METIS. METIS will be able to detect a variety of circumplanetary disks via their fundamental 12CO ro-vibrational line emission in only 60 s of total detector integration time.

The Extremely Large Telescope

Extremely large telescopes (ELTs) are considered worldwide to be one of the highest priorities in ground-based astronomy. The European Southern Observatory (ESO) is developing an ELT that will have a 39 m main mirror and will be the largest visible and infrared light telescope in the world. The ELT will be equipped with a lineup of cutting-edge instruments, designed to cover a wide range of scientific possibilities. The leap forwards with the ELT can lead to a paradigm shift in our perception of the Universe, much as Galileo's telescope did 400 years ago. We illustrate here the various components of the ELT, including the dome and main structure, the five mirrors, and the telescope systems. We then describe the ELT instrumentation and some of the astronomical topics it will address. We then conclude by examining the synergies with other astronomical facilities.

Redshift drift cosmography with ELT and SKAO measurements

ABSTRACT Mapping the expansion history of the universe is a compelling task of physical cosmology, especially in the context of the observational evidence for the recent acceleration of the universe, which demonstrates that canonical theories of cosmology and particle physics are incomplete and that there is new physics still to be discovered. Cosmography is a phenomenological approach to cosmology, where (with some caveats) physical quantities are expanded as a Taylor series in the cosmological redshift z, or analogous parameters such as the rescaled redshift y = z/(1 + z) or the logarithmic redshift x = ln (1 + z). Moreover, the redshift drift of objects following cosmological expansion provides a model-independent observable, detectable by facilities currently under construction, viz. the Extremely Large Telescope and the Square Kilometre Array Observatory (at least in its full configuration). Here, we use simulated redshift drift measurements from the two facilities to carry out an assessment of the cosmological impact and model discriminating power of redshift drift cosmography. We find that the combination of measurements from the two facilities can provide a stringent test of the Λ cold dark matter paradigm, and that overall the logarithmic-based expansions of the spectroscopic velocity drift are the most reliable ones, performing better than analogous expansions in the redshift or the rescaled redshift: the former nominally gives the smaller error bars for the cosmographic coefficients but is vulnerable to biases in the higher order terms (in other words, it is only reliable at low redshifts), while the latter always performs poorly.

Super-resolution wavefront reconstruction

Context.Cutting-edge, ground-based astronomical instruments are fed by adaptive optics (AO) systems that are aimed at providing high performance down to the visible wavelength domain on 10 m class telescopes and in the near infrared for the first generation instruments of Extremely Large Telescopes (ELTs). Both applications lead to a large ratio between the telescope diameter,D, and the coherence length or Fried parameter,r0, that isD/r0. As the parameter that defines the required number of degrees of freedom of the AO system,D/r0drives the requirement to reconstruct the incoming wavefront with ever-higher spatial resolution. In this context, super-resolution (SR) appears as a potential game changer. Indeed, SR promises to dramatically expand the range of spatial frequencies that can be reconstructed from a set of lower resolution measurements of the wavefront.Aims.As a technique that seeks to upscale the resolution of a set of measured signals, SR retrieves higher-frequency signal content by combining multiple lower resolution sampled data sets. It is well known both in the temporal and spatial domains and widely used in imaging to reduce aliasing and enhance the resolution of coarsely sampled images. This study applies the SR technique to the bidimensional wavefront reconstruction. In particular, we show how SR is intrinsically suited for tomographic multi-wavefront sensor (WFS) AO systems, revealing many of its advantages with minimal design effort.Methods.We provide a direct space and Fourier optics description of the wavefront sensing operation and we demonstrate how SR can be exploited through signal reconstruction, especially within the framework of periodic non-uniform sampling. We investigate both meta-uniform and non-uniform sampling schemes and we show that under some conditions, both sampling schemes enable a perfect reconstruction of band-limited signals. We also provide a SR bi-dimensional model for a Shack-Hartmann (SH) WFS, along with an analysis of the characteristics of the sensitivity function. We validated the SR concept with numerical simulations of representative multi-WFS SH AO systems. Finally, we explored the extension of the method to pyramid WFSs.Results.Our results show that combining several WFS samples in a SR framework grants access to a greater number of modes than the native one offered by a single WFS (despite the fixed sub-aperture size across samples). We show that the wavefront reconstruction achieved with four WFSs can be equivalent to a single WFS providing a sampling resolution that is twice greater (linear across the telescope aperture). We also show that the associated noise propagation is not degraded under SR. Finally, we show that the concept can be extended to the signal produced by single pyramid WFS, with its four re-imaged pupils serving as multiple non-redundant samples.Conclusions.We find that SR applied to wavefront sensing and reconstruction (WFR) offers a new parameter space to explore, as it decouples the size of the sub-aperture from the desired wavefront sampling resolution. By shifting away from outdated assumptions, new and more flexible, better-performing AO designs have now become possible.

New capabilities for laser holographic testing during assembly and collimation of large segmented telescope mirrors

Subject of study. Several novel options for interferometric testing of large aspheric segmented primary telescope mirrors during all phases of construction (assembly, collimation, and performance assessment) are proposed. In this paper, we will describe and validate new engineering design solutions for interferometric surface testing of large concave aspheric segmented telescope mirrors. Methods. All proposed test configurations are based on a reflecting optical compensator in the form of an axial synthetic holographic optical element or a reflective convex aspheric surface of revolution. We propose a quasi-autocollimative light path in which an optical compensator reverses the object wavefront; however, the object wavefront itself does not directly produce the image of the surface being tested in the plane where the interference and shadow patterns are recorded, thereby eliminating significant distortion-like errors. Main results. We provide the calculated parameters for quasi-autocollimative systems used to test the surfaces of the aspheric concave primary mirror segments of four well-known world-class telescopes: the Millimetron telescope, diameter 10 m; the James Webb Space Telescope, diameter 6.5 m; the Extremely Large Telescope (ELT), diameter 39.3 m; and the postponed European Southern Observatory conceptual design known as the Overwhelmingly Large Telescope (OLT), diameter 100 m. We show that simultaneous use of a series of similar coaxial optical compensators on the object leg of the interferometer will almost completely eliminate any restrictions related to the size, asphericity, and curvature of aspheric segments of primary mirrors in telescopes. Using a conical substrate for the working surface of the holographic compensator will substantially reduce the maximum spatial frequency of the compensator. The calculations were performed using Mathcad and Zemax. We propose that traditional non-autocollimative laser holographic test configurations without wavefront reversal be used on the object leg during the initial assembly of the primary mirror segments. Laser holographic topography is also suitable for this purpose. Practical significance. The novel ideas, methods, and systems engineering solutions proposed here are based on wavefront reversal by a reflecting optical compensator or a series (“chain”) of such compensators and will support in-process testing and certification testing of aspheric primary mirror segments, with interferometric accuracy, for any of the optical telescopes currently operating or under development, whether ground based or space based. These capabilities will support full-scale interferometric testing of the 12 m diameter Millimetron aspheric segmented primary mirror initially proposed by Academician N. S. Kardashev, but will also undoubtedly be especially important for space-based telescopes.

High-resolution spectral models of TRAPPIST-1e seen as a Pale Blue Dot for ELT and JWST observations

ABSTRACT Rocky exoplanets orbiting in the habitable zone (HZ) of nearby M dwarfs provide unique opportunities for characterizing their atmospheres and searching for biosignature gases. TRAPPIST-1e, a temperate Earth-sized exoplanet in the HZ of a nearby M dwarf, is arguably the most favourable target for ground- and space-based atmospheric characterization by the extremely large telescopes (ELTs) and the James Webb Space Telescope. To inform future observations in reflected and emitted lights using these upcoming telescopes, we simulate the high-resolution reflection and emission spectra for TRAPPIST-1e for both modern and prebiotic Earth-like atmospheric compositions. To demonstrate the effects of wavelength-dependent albedo on climate and spectra, we further simulate five albedo scenarios for each atmospheric composition: cloudy modern Earth-like, cloud-free modern Earth-like, cloudy ocean planet, 100 per cent cloudy planet, and wavelength-independent albedo of 0.31. We use the recent Mega-MUSCLES spectral energy distribution of TRAPPIST-1 for our models. We show that the O2 + CH4 and O3 + CH4 biosignature pairs as well as climate indicators (CO2 and H2O) show features in both high-resolution reflection and emission spectra of TRAPPIST-1e that the ELTs can search for. Our high-resolution data base for modern and prebiotic Earth TRAPPIST-1e models with various surface compositions and cloud distributions provides a tool for observers to train retrieval algorithms and plan observation strategies to characterize this potentially habitable world.

Observability of forming planets and their circumplanetary discs – IV. With JWST and ELT

ABSTRACT To understand the potential for observing forming planets and their circumplanetary discs (CPDs) with James Webb Space Telescope (JWST) and Extremely Large Telescope (ELT), we created mock observations from three-dimensional radiative hydrodynamic simulations and radiative transfer post-processing for planets with 10, 5, and 1 Jupiter and 1 Saturn masses with orbital separation of 50 and 30 au in 0, 30, and 60○ inclinations. Instrumental effects were then simulated with Mirage for JWST/NIRCam and NIRISS, MIRISim for JWST/MIRI, and SimCADO and SimMETIS for ELT/MICADO and METIS. We found that the longer wavelengths (mid-infrared and beyond) are the best to detect CPDs, since they allow CPD of planet with smaller mass to be detected. MIRI on JWST and METIS on ELT offer the best possibility on these telescopes. Specifically, below 3 $\mu{\rm m}$, only 10 MJup planets with their CPDs are detectable with NIRCam and MICADO. 5 MJup planets are only detectable if at 30 au (i.e. closer) orbital separation. Planets above 5 MJup with their CPDs are detectable between 3 and 5 $\mu{\rm m}$ with NIRCam and METIS L/M band, or above 10 $\mu{\rm m}$ with MIRI and METIS N band. For ≤1 MJup planets >15 $\mu{\rm m}$ are needed, where MIRI uniquely offers imaging capability. We present magnitudes and spectral energy distributions for separate components of the planet + CPD + circumstellar disc (CSD) system, to differentiate the extinction rates of CPDs and CSDs and to provide predictions for observational proposals. Because the CPD turns out to be the main absorber of the planet’s emission, especially <10 $\mu{\rm m}$, this makes the detection of forming planets quite challenging.