Radio-frequency interference detection and flagging is one of the most difficult and urgent problems in 21 cm Epoch of Reionisation research. In this work, we present $\chi^2$ from redundant calibration as a novel method for RFI detection and flagging, demonstrating it to be complementary to current state-of-the-art flagging algorithms. Beginning with a brief overview of redundant calibration and the meaning of the $\chi^2$ metric, we demonstrate a two-step RFI flagging algorithm which uses the values of this metric to detect faint RFI. We find that roughly 27.4% of observations have RFI from digital television channel 7 detected by at least one algorithm of the three tested: 18.0% of observations are flagged by the novel $\chi^2$ algorithm, 16.5% are flagged by SSINS, and 6.8% are flagged by AOFlagger (there is significant overlap in these percentages). Of the 27.4% of observations with detected DTV channel 7 RFI, 37.1% (10.2% of the total observations) are detected by $\chi^2$ alone, and not by either SSINS or AOFlagger, demonstrating a significant population of as-yet undetected RFI. We find that $\chi^2$ is able to detect RFI events which remain undetectable to SSINS and AOFlagger, especially in the domain of long-duration, weak RFI from digital television. We also discuss the shortcomings of this approach and discuss examples of RFI which seems undetectable using $\chi^2$ while being successfully flagged by SSINS and/or AOFlagger.

Passive services (e.g. radio astronomy, Earth observing) are slowly responding to new radio frequency interference (RFI) challenges to their science missions, particularly those arising from constellations of communication satellites. We will report on efforts at the National Radio Astronomy Observatory and Green Bank Observatory to detect, characterize and mitigate RFI impacts at our sites, including (a) preliminary results from a prototype spectrum monitor located at Green Bank; (b) results from a 1.5-year study of the impacts of Starlink transmissions (satellites and user terminals) on the Very Large Array, indicating minimal interference; (c) our plans for real-time status coordination of telescope control systems with satellite operators to avoid RFI conflicts with observing programs. Future scientific endeavors such as the next-generation Very Large Array will operate in a more complex spectral environment than the current generation of radio telescopes, and the ability to accurately detect, characterize and effectively mitigate RFI is critical.

We present a search for the presence of additional exoplanets in previously identified multi-planetary systems, using the Titius-Bode (TB) relation, a logarithmic distance between planets in our solar system. We analyze 229 multi-planetary systems, each containing a minimum of three confirmed planets, by modeling the TB relation employing the Markov Chain Monte Carlo (MCMC) technique. Our findings indicate that ∼53% of these systems exhibit a logarithmic spacing relation more pronounced than that observed in the solar system. We predict the existence of 426 supplementary exoplanets within these 229 systems, identifying 197 candidates through interpolation and 229 through extrapolation. Among the predicted planets, 47 are located in the habitable zone of their respective host stars. Within this subset, five planets have a maximum radius below 1.25R⊕ and an estimated mass between 0.1 and 2M⊕. We minimize inaccuracies in the orbital period estimation for the anticipated planets compared to the earlier studies.

In order to make the European communication infrastructure more resilient and to strengthen the technological sovereignty in space, the European Parliament and the European Council decided in November 2022 to build a new satellite constellation: IRIS2-Infrastructure for Resilience, Interconnectivity and Security by Satellite. The constellation will be realised through several hundred satellites in multiple orbits and is intended to ensure secure and very fast connectivity for commercial and institutional channels even in places where terrestrial broadband is not feasible or economical. The constellation must also meet the EU’s “Green Deal” requirements (avoiding an increase in space debris, protection of other services), use the latest technologies and optimally protect communications against cyber-attacks by applying quantum encryption. The aim of this paper is to provide a deeper insight into the constellation’s architecture, regulations and challenges. The importance of working in committees like DG DEFIS and having a large network will also be discussed in order to advance the Dark and Quiet Skies efforts.

The increasing addition of meteor showers to the International Astronomical Union (IAU) list underscores the need for more accurate identification of new parent bodies, especially with the growing availability of video meteor data. Current methods using a high-threshold single-linking Dsh criterion often lack accuracy, prompting our study to explore advanced techniques for linking meteors to their parent bodies. Using the Moroccan meteor observation network as a foundation, we applied and compared several methods on the SonotaCo and EDMOND databases to detect new parent bodies. We further applied rigorous statistical tests to avoid random associations. This presentation highlights the network’s innovative methodology, its success in accurately tracing meteoroid origins, and its potential to predict impact zones on Earth (Guennoun et al.(2019)). Through collaborative efforts, this network provides a significant contribution in the study of meteor dynamics.

U.S. adaptive optics telescopes using laser guide stars for an artificial reference source are impacted by the presence of satellite constellations (SATCONs) because of the requirement to follow Department of Defense laser deconfliction protocol as administered by the U.S. Space Command’s Laser Clearinghouse. The Laser Deconfliction protocol is designed to protect damage to satellites and their operation due to inadvertent illumination. As SATCONs begin to dominate the number of satellites in orbit they contribute highly to the number of closure windows when the astronomical lasers cannot be propagated. If left unchecked, the proposed number of SATCONs over the next decade will severely impact the laser open-shutter time, especially for the U.S. extremely large telescopes (US-ELTs) reducing the competitiveness of U.S. astronomical adaptive optics. Mitigation of the closure windows is therefore important.

Spectroscopy of artificial space objects is a method utilised to retrieve the reflectance spectra of satellites, providing valuable information about the surface properties and material composition of objects. However, the reflectance spectrum of an object tends to slightly change over time, in a way that implies the surface shifting to redder colour hues and darkening overall. The causes of this reddening effect are up to this day unknown, although the leading explanation is the deterioration of surface materials due to exposure to the harsh environment of space. Large satellite constellations are ideal for the analysis of this effect. The studied data were obtained by AMOS - All-Sky Meteor Orbit System - developed by the Comenius University in Bratislava, Slovakia. Specular glints of Iridium satellites recorded over the course of six years are analysed to provide further insight into the explanation of the reddening effect.

The International Institute of Space Law (IISL) is the largest worldwide association of space lawyers. In 2021, IISL created a Working Group (WG) on light pollution of the night sky caused by space objects, particularly by satellite constellations. The WG completed its research early in 2023 and issued a report that was adopted by IISL in June 2023. The report shows that light pollution generated by spacecraft in the optical range is a new problem that is currently unregulated. However, a number of existing and emerging rules in international law and in the domestic laws of many countries support the protection of astronomy and the night sky. The eventual adoption of standards limiting the brightness of satellites as well as international agreements protecting dark skies was also explored by the WG. The author, in his capacity as coordinator of the WG, summarizes the contents of the report and explores its implications.

Beginning in 2022, light pollution and grassroots advocacy expert Amy C. Oliver FRAS began partnering with DarkSky International (formerly International Dark-Sky Association) to increase traditional and social media coverage of International Dark-Sky Week through the strategic use of proclamations and other ceremonial documents and recognitions throughout their global advocate network. While the year-over-year growth of the proclamations programme and the resultant media attention provide mathematical performance indicators of success, intangible successes have also become evident through the increased confidence of DarkSky advocates and their willingness to engage in both grassroots and policy conversations regarding dark and quiet skies. Previously reported results from ASP2022, Solar Eclipses to Space Telescopes: Communicating Science to Students and the Public, and its forthcoming Proceedings are updated herein, along with additional and new learnings previously unreported.

This article summarizes recent findings of the CPS Work Package 2 Working Group concerning international law and policy relevant to the protection of dark and quiet skies. It identifies existing gaps in the understanding and application of relevant international instruments, extracts lessons learned from previous analyses, and proposes future steps to address orbital light and spectrum pollution. In particular, the article emphasizes the need to use multiple approaches alongside space law, such as policy advocacy and public engagement, to diversify strategies and achieve more effective solutions.

Liquid water can exist on exoplanets in a circumstellar region significantly wider than the Conservative Habitable Zone (CHZ). In particular, tidally locked planets orbiting closer inwards than the inner CHZ border could have liquid water on their night side provided the heat transport between the day and night side is low. Planets further away than the outer CHZ boundary can maintain subglacial liquid water if they have geothermal heat sources or in the form of subglacial lakes similar to the Martian polar lakes. Pressurized water can reach the planetary surface through faults and cracks in the ice cover, creating plumes and enriching the atmosphere with molecules that may be present in subglacial oceans. We discuss the model and the conditions needed to detect water and other molecules in the transmission spectrum by JWST, as have recently been detected in small hot exoplanets such as GJ287 b.

Earth’s and Venus’ atmosphere mass and composition today are accumulated results of the solar hydrologic cycle over billions of years with comet collisions infusing gassy material onto the planets and solar wind blowing away the lighter gasses leaving primarily only carbon dioxide and nitrogen on both Earth and Venus. The comets entering the inner solar system have higher evaporation rate than collision probability, resulting in far less mass infusion onto inner planets than outer planets. The infused gasses onto the Earth are further processed by its chemical processes. Being too close to the Sun to have liquid water, Venus lacks chemical processes. The solar hydrologic cycle theory predicts comet mass infusion ratio between Venus and Earth to be 1:0.76. Comparing carbon dioxide and nitrogen mass in Venus atmosphere with nitrogen mass in Earth atmosphere plus carbon and nitrogen deposits in the crust, the ratio is 1:0.45-0.54.

As the number and variety of communications satellites proliferate in the rapidly accelerating New Space Age, specialists and lay observers alike have weighed the implications of a crowded orbital environment for astronomical research. Although so-called “megaconstellations” may be a relatively new development, conflict over the anticipated effects of space technology on astronomy has a much longer history, going back to the very first experimental communications satellites. Astronomers have long acted as environmental watchdogs for outer space even as the power landscape in the international aerospace industry shifted during the half century since Sputnik. What lessons might current astronomers take from past conflicts over the integrity of the night sky to address contemporary and future risk?

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.