Context.
Keplerian-Stacker is an algorithm capable of combining multiple observations acquired at different epochs by taking into account the orbital motion of a potential planet present in the ...images to boost the ultimate detection limit. In 2019, a total of 100 h of observation was allocated to Very Large Telescope (VLT) Spectrometer and Imager for the mid-infrared (VISIR) instrument for the New Earths in the
α
Centauri Region (NEAR) survey, a collaboration between European Southern Observatory (ESO) and Breakthrough Initiatives, to search for low mass planets in the habitable zone of the
α
Cen AB binary system. A weak signal
(S/N ~
3) was reported around
α
Cen A, at a separation of ≃ 1.1 au, corresponding to the habitable zone.
Aims.
Our study is aimed at determining whether K-Stacker is also capable of detecting the low-mass planet candidate with similar orbital parameters, which was previously found by the NEAR team. We also aim to search for additional potential candidates around a Cen A by utilizing the orbital motion to boost the signal and by generally placing stronger constraints on the presence of other planets in the system.
Methods.
We re-analysed the NEAR data using K-Stacker. This algorithm is a brute-force method that is equipped to find planets in observational time series and to constrain their orbital parameters, even if they have remained undetected in a single epoch.
Results.
We scanned a total of about 3.5 × 10
5
independent orbits, among which close to 15% correspond to fast-moving orbits on which planets cannot be detected without taking into account the orbital motion. We found only a single planet candidate that matches the C1 detection reported in Wagner et al. (2021, Nat. Commun., 12, 922). However, since this constitutes a re-analysis of the same data set, more observations will be necessary to confirm that C1 is indeed a planet and not a disk or other data artifact. Despite the significant amount of time spent on this target, the orbit of this candidate remains poorly constrained due to these observations being closely distributed across 34 days. We argue that future single-target deep surveys would benefit from a K-Stacker based strategy, where the observations would be split over a significant part of the expected orbital period to better constrain the orbital parameters.
Conclusions.
This application of K-Stacker to high-contrast imaging data in the mid-infrared demonstrates the capability of this algorithm in aiding the search for Earth-like planets in the habitable zone of the nearest stars with future instruments of the E-ELT, such as METIS.
Giant exoplanets on wide orbits have been directly imaged around young stars. If the thermal background in the mid-infrared can be mitigated, then exoplanets with lower masses can also be imaged. ...Here we present a ground-based mid-infrared observing approach that enables imaging low-mass temperate exoplanets around nearby stars, and in particular within the closest stellar system, α Centauri. Based on 75-80% of the best quality images from 100 h of cumulative observations, we demonstrate sensitivity to warm sub-Neptune-sized planets throughout much of the habitable zone of α Centauri A. This is an order of magnitude more sensitive than state-of-the-art exoplanet imaging mass detection limits. We also discuss a possible exoplanet or exozodiacal disk detection around α Centauri A. However, an instrumental artifact of unknown origin cannot be ruled out. These results demonstrate the feasibility of imaging rocky habitable-zone exoplanets with current and upcoming telescopes.
ESO, in collaboration with the Breakthrough Initiatives, has modified the VLT mid-infrared imager VISIR to greatly enhance its ability as a planet finder. It has conducted a 100-hour observing ...campaign to search for low-mass planets around both components of the binary a Centauri, part of the closest stellar system to the Earth. Using adaptive optics and high-performance coronagraphy, the instrument reached unprecedented contrast and sensitivity allowing it to see Neptune-sized planets in the habitable zone, if present. The experiment allowed us to characterise the current limitations of the instrument. We conclude that the detection of rocky planets similar to Earth in the habitable zone of the a Centauri System is already possible with 8-metre-class telescopes in the thermal infrared.
Vortex coronagraphs have been shown to be a promising avenue for high-contrast imaging in the close-in environment of stars at thermal infrared (IR) wavelengths. They are included in the baseline ...design of METIS. To ensure good performance of these coronagraphs, a precise control of the centering of the star image in real time is needed. We previously developed and validated the quadrant analysis of coronagraphic images for tip-tilt sensing estimator (QACITS) pointing estimator to address this issue. While this approach is not wavelength-dependent in theory, it was never implemented for mid-IR observations, which leads to specific challenges and limitations. Here, we present the design of the mid-IR vortex coronagraph for the new Earths in the \(\alpha\) Cen Region (NEAR) experiment with the VLT/VISIR instrument and assess the performance of the QACITS estimator for the centering control of the star image onto the vortex coronagraph. We use simulated data and on-sky data obtained with VLT/VISIR, which was recently upgraded for observations assisted by adaptive optics in the context of the NEAR experiment. We demonstrate that the QACITS-based correction loop is able to control the centering of the star image onto the NEAR vortex coronagraph with a stability down to \(0.015 \lambda/D\) rms over 4h in good conditions. These results show that QACITS is a robust approach for precisely controlling in real time the centering of vortex coronagraphs for mid-IR observations.
Giant exoplanets on wide orbits have been directly imaged around young stars. If the thermal background in the mid-infrared can be mitigated, then exoplanets with lower masses can also be imaged. ...Here we present a ground-based mid-infrared observing approach that enables imaging low-mass temperate exoplanets around nearby stars, and in particular within the closest stellar system, Alpha Centauri. Based on 75-80% of the best quality images from 100 hours of cumulative observations, we demonstrate sensitivity to warm sub-Neptune-sized planets throughout much of the habitable zone of Alpha Centauri A. This is an order of magnitude more sensitive than state-of-the-art exoplanet imaging mass detection limits. We also discuss a possible exoplanet or exozodiacal disk detection around Alpha Centauri A. However, an instrumental artifact of unknown origin cannot be ruled out. These results demonstrate the feasibility of imaging rocky habitable-zone exoplanets with current and upcoming telescopes.
The importance of a ‘more‐than‐human’ approach to architectural design is becoming ever clearer. While partly a response to global ecological disaster, this shift also reflects a recognition that ...design should not seek solely to solve human problems, but to create environments that facilitate emergent opportunities for a wide range of nonhuman occupants and processes. Jacopo Leveratto is based at the Politecnico di Milano, where he researches on radical forms of habitability and posthuman architecture. Here he describes five steps to achieving these aspirations.
Although the term habitat represents one of the most crucial ecological concepts for describing the relationship between some species and their environment, it is also one of the vaguest. This is ...why, in the past few years, it has often been replaced by more specific ones, which could clearly identify the relationships at stake. This is the case, for instance, of the term biotope, which recently, with the increasing awareness of ecosystem interconnectivity, has taken more and more relevance in comparison to the previous one. Whereas a habitat, in fact, is the sum of the physical and biotic resources of a place that allows the survival and reproduction of a particular species, a biotope represents the habitat not of a specific population, but of a whole biotic and sympoietic community. A feature that perfectly describes the characteristics of a new design approach, generally called more-than-human, here analyzed from both a theoretical and methodological standpoint, which today, to tackle major environmental challenges, focuses on building architectures in which multiple species can find some terms for cohabitation. And which, therefore, not only entails addressing a new class of subjects but also challenges the role of architects and other practitioners in this field by requiring new ways of designing that enhance interspecies coexistence and collaboration.
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