New apodization techniques are emerging rapidly to enhance the coronagraphs’ rejection capabilities and refine the optics for directly detecting exoplanets. One such technique, Interferometric Apodization by Homothety (IAH), involves splitting the incident Point Spread Function (PSF) into two using a 50 : 50 beamsplitter. One of the resulting PSFs has its amplitude reduced by a factor γ and its transverse dimension expanded by a factor ƞ. By combining these two PSFs, an apodized PSF is generated. In this study, we will use the standard values of γ and ƞ for both rectangular and circular apertures. We implement this approach in the laboratory using a Mach-Zehnder Interferometer with Cube Beamsplitters, chosen for their advantages over Plate Beamsplitters, including easy integration at a 0° angle of incidence and equal optical path lengths for reflected and transmitted light. This technique shows significant promise, achieving a contrast of approximately 5.10−3at small angular separations around 2.8 λ/D.

The search for extraterrestrial life, sapient or not, is a multi-phased process comprising pre-discovery, discovery, and post-discovery phases. Post-detection considerations can be conceptualized as contemplations of scientific and non-scientific issues pertinent partially to the discovery phase and to the final post-discovery phase that will be set in motion by a confirmed discovery of extraterrestrial life. To systematically explore the corresponding complex future landscape, scholars have proposed using alternative scenarios. However, this historical approach has actually focused more narrowly on generating specific detection situations, while neglecting the broader contextual environment scenarios that will necessarily encompass the detection. By drawing on Futures Studies, this work argues that a more comprehensive anticipatory approach is needed, involving the parallel delineation of both possible detection situations and possible future contextual scenarios, followed by their integration. Additionally, this work introduces a “Rehearsing Post-Detection Futures” workshop workflow inspired by the “Futures Literacy Laboratory” approach. This ready-to-deploy, interactive, participatory workshop is intended for educators and aims to help students and scholars in relevant disciplines broaden and diversify not only what but also how and why they anticipate when they consider the effects of a detection of extraterrestrial life in the future, particularly during the most urgent and precarious post-detection stage, i.e., the short-term stage right after the detection and its communication, thereby facilitating the cultivation of the participants’ futures literacy. Such interventions can support the mindful deployment of a critical-hermeneutic anticipatory perspective towards building a more responsible search for extraterrestrial life, sapient or not.

Expert working groups produced a number of thoughtful technical recommendations to policy makers and industry to mitigate the impact of satellite constellations on astronomical observations. The IAU CPS has undertaken to consolidate those complementary recommendations into a compact set, with advice to industry and policy makers, as well as identification of needs for further definition by the astronomy community.

We are imaging Gaia-selected young massive white dwarfs in the 40 pc solar neighborhood with the ESO-VLT (ERIS LGS AO instrument) to search for >5 Jupiter mass companions. These white dwarfs have 2.5-5 M⊙ Main Sequence (MS) progenitors, and offer the unique possibility to test the formation of giant planets around intermediate mass stars, assuming these planets can survive post-MS evolution of their host stars. White dwarfs feature key advantages over their progenitor MS stars to spatially resolve giant planet companions in terms of (1) contrast and (2) angular separation. We limit ourselves to young white dwarfs with total ages (MS lifetime + white dwarf cooling age) < 1 Gyr which assures that any giant planets would be self-luminous and bright enough to be detectable (H-band < 25 mag). So far, we have obtained high angular resolution data for 10 white dwarfs with VLT/ERIS, with no confirmed detections, which might imply giant planets do not form around intermediate-mass MS stars, due to the rapid photoevaporation of their circumstellar disks caused by the host stars’ elevated FUV and X-ray irradiation. We keep searching.

With billions of planets in the galaxy, advanced civilizations could relocate planets within or into their planetary systems rather than destroy entire planetary systems to construct megastructures. Such shifts could create Strange Exoplanetary Architectures (SEA), with unusual planetary arrangements potentially indicating deliberate actions by extraterrestrial intelligence (ETI). Searching for biosignatures and technosignatures in these systems could be a promising method for detecting ETI activities.

This study addresses the growing concern in the astronomical community regarding the brightness and interference caused by low Earth orbit (LEO) communication satellites. Utilising data from a global network of telescopes and a custom Python pipeline, we analysed 369 observations of 159 OneWeb satellites obtained in the BVRI bandpasses with the Danish 1.54-metre telescope at ESO La Silla, Chile, revealing significant variations in brightness across different wavelengths and a substantial proportion exceeding recommended brightness limits. Our preliminary findings, incorporating diffuse sphere phase models, offer further insights into the satellite’s reflective properties and implications for future astronomical observations.

How may life be defined? This is a question that has growing importance as humanity develops the ability to explore beyond the Earth and searches for evidence of life being present on other astronomical bodies from the planets and moons in our own solar system to the thousands of exoplanets we are detecting around other stars. Such a definition is non-trivial and, as we discover life in ever more diverse and ‘extreme’ environments on Earth broadening the regions of ‘habitability’, increasingly complex. In this short article, we review the different definitions of ‘life’, the need for such a definition and the implications that such a definition may have on the future development of astrobiology and the search for evidence of life in the universe.

This paper introduces the SETI Post-Detection Hub, its origins, motivations, and initial undertakings, as well as the rationale for such an endeavour - to explore and develop thorough and integrated approaches in preparation for a potential discovery event in the Search for Extraterrestrial Intelligence (SETI). Officially launched at the University of St Andrews in 2022, it brings together a highly multidisciplinary international team of experts.

From the outset, our rationale has been to weave together insights from diverse fields, including governance, impact strategies, analytics, and the humanities, with particular attention to the inclusion of all humanity’s cultural voices – a vital requirement to fully understand our challenge and its solutions. So, in preparation for the discovery of extraterrestrial life, the Hub will endeavour to grow readiness for complex futures by fostering a synergistic environment that encourages imaginative, methodical preparation, to stir transformative interdisciplinary and diverse engagement.

In this article, I analyze the claim that alien life could be “weird”. I propose to distinguish between two types of astrobiological weirdness: a naturalistic and an epistemic one. Weirdness, naturalistically construed, is an attribute for astrobiological traits. Weirdness, epistemically construed, is an attribute for scientific hypotheses and theories about the nature of such traits.

The prospect of human contact with extraterrestrial intelligence (ETI) carries profound societal implications, far surpassing the impact of discovering non-sentient microbes on distant planets. Such an encounter would reverberate throughout human society, challenging established beliefs, including theological doctrines, and reshaping our cosmic perspective. During the last decade, the search for extraterrestrial intelligence (SETI) and non-intelligent extraterrestrial life has received notable attention in digital media and newspapers and influenced public thoughts and perceptions about astrobiology, SETI and planetary science fields. This abstract takes a science communication and society perspective, evaluating our current decision-making processes and policies in anticipation of potential discoveries and their consequential interactions with varying forms of extraterrestrial life, including public attitudes, news dissemination and rumour control, and decoding and messaging ETIs.

As the number of large Earth-orbiting satellite networks (i.e., mega-constellations or mega-sats) increases, so does the threat posed to astronomical research. Bright satellite trails in exposures of the night sky can affect the quality of observations and hinder science objectives. Using the MASCARA station to detect satellites from the SpaceX Starlink network as a representative case, this study quantifies the present and future impact of mega-sats on ground-based optical astronomy. We find that further design revisions are required to mitigate the brightness concern of pre-Gen2 Starlinks and that hundreds of satellites could be visible in all-sky observations at peak observing times if additional measures are not taken.

We explore the position and stability of the collinear Lagrangian points in the Restricted Three-Body Problem (RTBP) where one primary body is radiative and the other is oblate. We examine the influence of Poynting-Robertson drag and the position and stability of the Lagrangian points which are affected by variations in the radiation parameter and oblateness. We compare our results with ten exoplanet systems, to identify locations in these exoplanet systems where one can detect asteroids, primodial material, or seeds where planet formation can take place. Moreover, for all ten planetary systems examined in this study, the Lagrangian points are unstable and may be possible locations where minor planets, asteroids, or debris can be found. The instability of the Lagrangian points can also be a possible cause of relocation and migration of planetesimals. These could also be used as possible candidates for observations with the James Webb.

“Il cielo in salotto” (in English, “The sky in your living room”) is a format for live streaming astronomical observations created by the Italian National Institute for Astrophysics (INAF). The project started in late 2020 in the midst of the Covid-19 pandemic to engage the general public and students with astronomy and space science remotely, when observatory visits were not possible. The format later evolved, in the “new normal” scenario, as a complementary activity to in-person events, featuring astronomical phenomena - such as planet alignments, eclipses, different Moon phases, comets, sunspots, exoplanet-hosting stars - observed live by the INAF network of telescopes all around the country. These events are enriched by live interviews with INAF researchers and supported by large-scale public engagement campaigns conducted together with space enthusiasts, amateur astronomy associations and other partners. Viewers can ask questions live to the experts and also select some of the targets to observe. We present lessons learnt and best practices from three and a half years running the project, along with some of the technical and logistics, content and communication solutions adopted in the format of potential interest to colleagues organising similar events in other countries. We also discuss the results of a focus group conducted for three years in a row during the summer “SuperMoon” broadcasts, a regular programme taking advantage of the popularity of this event in the news to cover current topics in planetary science.

The study of cosmic rays (CRs) and their interactions with exoplanetary atmospheres and stellar environments can provide essential insights into the habitability and atmospheric chemistry of these distant worlds. For instance, on Earth, radiation from cosmic rays constitutes only about 10 percent of the total radiation exposure at ground level, but this percentage can be significantly higher for planets orbiting stars close to cosmic ray sources. Furthermore, the modulation of cosmic rays varies considerably among different stars. This research focuses on modelling the modulation of CRs by various stellar types, particularly F, G, K, and M stars, to understand the impact on exoplanets in their habitable zones. Employing an analytical one-dimensional model of the Cosmic Ray Transport Equation, which allows us to study a wide range of parameters, we analyse how different stellar parameters, such as wind speed and magnetic field strength, influence the cosmic ray environment. The developed model simulates the cosmic ray spectra and mean free path, considering factors like the star’s relative motion through the interstellar medium. This work aims to contribute to the understanding of radiation conditions on exoplanets, which is crucial for assessing their potential to support life. It offers a preliminary but meaningful exploration into the complex interactions between cosmic rays and exoplanetary environments, shedding light on factors that might influence the habitability of these alien worlds.

Exoplanet follow-up with JWST requires precise masses and radii. HARPS-N is a high-resolution spectrograph on the Telescopio Nazionale Galileo (TNG), predominantly used to detect and characterize exoplanets using the radial velocity (RV) method. The HARPS-N Collaboration has been characterising exoplanets with HARPS-N for over a decade. In this short paper we highlight the contributions that the HARPS-N Collaboration has made to the characterisation of small exoplanets.

The rising number of exoplanet discoveries and advances in machine learning (ML) techniques present new possibilities for exploring and understanding the characteristics of worlds beyond our solar system. This research examines the exoplanet dataset by applying ML techniques to categorize these systems, uncover relationships among their physical features, and predict the exoplanet radius. We group the data into two primary categories: ‘small’ and ‘giant’ planets, with thresholds at Rp = 8.13R⊕ and Mp = 52.48M⊕. Our study indicates that the planetary mass, orbital period, and stellar mass play critical roles in predicting the exoplanet radius. A notable finding of our research is that small planets exhibit a positive linear mass-radius relationship, consistent with other studies. Conversely, for giant planets, we observe a strong correlation between planetary radius and the mass of their host stars, potentially providing significant insights into the relationship between giant planet formation and stellar properties.

We discuss that, when considering discovery or searching for life on other planets, we have to take note that such life could be in any comparative time snapshot. Furthermore, the evolutionary scenario might work out differently, depending on the initial conditions.

Whether an exoplanet can retain its atmosphere is mainly controlled by the extreme-ultraviolet (EUV) radiation received from its host star, and the photo-chemistry in its outer atmosphere is driven by the far-ultraviolet radiation, primarily the hydrogen Lyman-α line, from its host star. Since interstellar hydrogen absorbs most of this EUV and Lyman-α radiation, there is a critical need for accurate reconstruction techniques to identify the intrinsic EUV and Lyman-α radiation that impacts the outer atmosphere of an exoplanet. This paper describes and critiques the available reconstruction techniques.

This article examines four different points where an astrological or astrobiological discovery might propose a challenge for Christian religion. These points of contact are the size of the cosmos, human uniqueness, Christological considerations and the ultimate fate of the cosmos. I argue that the most popular interpretations of these challenges are not very serious, while there are certain issues that may genuinely push Christian religion and theology to reconsider some topics in their belief system.

The CHaracterising ExOPlanet Satellite (CHEOPS) is a partnership between the European Space Agency and Switzerland with important contributions by 10 additional ESA member States. It is the first S-class mission in the ESA Science Programme. CHEOPS has been flying on a Sun-synchronous low Earth orbit since December 2019, collecting millions of short-exposure images in the visible domain to study exoplanet properties.

A small yet increasing fraction of CHEOPS images show linear trails caused by resident space objects crossing the instrument field of view. CHEOPS’ orbit is indeed particularly favourable to serendipitously detect objects in its vicinity as the spacecraft rarely enters the Earth’s shadow, sits at an altitude of 700 km, and observes with moderate phase angles relative to the Sun. This observing configuration is quite powerful, and it is complementary to optical observations from the ground.

To characterize the population of satellites and orbital debris observed by CHEOPS, all and every science images acquired over the past 3 years have been scanned with a Hough transform algorithm to identify the characteristic linear features that these objects cause on the images. Thousands of trails have been detected. This statistically significant sample shows interesting trends and features such as an increased occurrence rate over the past years as well as the fingerprint of the Starlink constellation. The cross-matching of individual trails with catalogued objects is underway as we aim to measure their distance at the time of observation and deduce the apparent magnitude of the detected objects.

As space agencies and private companies are developing new space-based surveillance and tracking activities to catalogue and characterize the distribution of small debris, the CHEOPS experience is timely and relevant. With the first CHEOPS mission extension currently running until the end of 2026, and a possible second extension until the end of 2029, the longer time coverage will make our dataset even more valuable to the community, especially for characterizing objects with recurrent crossings.