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Analysing greenhouse gas emissions of an astronomical institute is a first step to reducing its environmental impact. Here, we break down the emissions of the Max Planck Institute for Astronomy in Heidelberg and propose measures for reductions.

A wide variety of scenarios for the origin of life have been proposed, with many influencing the prevalence and distribution of biosignatures across exoplanet populations. This relationship suggests these scenarios can be tested by predicting biosignature distributions and comparing them with empirical data. Here, we demonstrate this approach by focusing on the cyanosulfidic origins-of-life scenario and investigating the hypothesis that a minimum near-ultraviolet (NUV) flux is necessary for abiogenesis. Using Bayesian modeling and the \\bioverse\\ survey simulator, we constrain the probability of obtaining strong evidence for or against this ``UV Threshold Hypothesis'' with future biosignature surveys. Our results indicate that a correlation between past NUV flux and current biosignature occurrence is testable for sample sizes of \\(\\gtrsim\\)50 planets. The diagnostic power of such tests is critically sensitive to the intrinsic abiogenesis rate and host star properties, particularly maximum past NUV fluxes. Surveys targeting a wide range of fluxes, and planets orbiting M dwarfs enhance the chances of conclusive results, with sample sizes \\(\\gtrsim\\)100 providing \\(\\gtrsim\\)80\\% likelihood of strong evidence if abiogenesis rates are high and the required NUV fluxes are moderate. For required fluxes exceeding a few hundred erg/s/cm\\(^2\\), both the fraction of inhabited planets and the diagnostic power sharply decrease. Our findings demonstrate the potential of exoplanet surveys to test origins-of-life hypotheses. Beyond specific scenarios, this work underscores the broader value of realistic survey simulations for future observatories (e.g., HWO, LIFE, ELTs, Nautilus) in identifying testable science questions, optimizing mission strategies, and advancing theoretical and experimental studies of abiogenesis.

Long-term magma ocean phases on rocky exoplanets orbiting closer to their star than the runaway greenhouse threshold - the inner edge of the classical habitable zone - may offer insights into the physical and chemical processes that distinguish potentially habitable worlds from others. Thermal stratification of runaway planets is expected to significantly inflate their atmospheres, potentially providing observational access to the runaway greenhouse transition in the form of a \"habitable zone inner edge discontinuity\" in radius-density space. Here, we use Bioverse, a statistical framework combining contextual information from the overall planet population with a survey simulator, to assess the ability of ground- and space-based telescopes to test this hypothesis. We find that the demographic imprint of the runaway greenhouse transition is likely detectable with high-precision transit photometry for sample sizes \\(\\gtrsim 100\\) planets if at least ~10 % of those orbiting closer than the habitable zone inner edge harbor runaway climates. Our survey simulations suggest that in the near future, ESA's PLATO mission will be the most promising survey to probe the habitable zone inner edge discontinuity. We determine survey strategies that maximize the diagnostic power of the obtained data and identify as key mission design drivers: 1. A follow-up campaign of planetary mass measurements and 2. The fraction of low-mass stars in the target sample. Observational constraints on the runaway greenhouse transition will provide crucial insights into the distribution of atmospheric volatiles among rocky exoplanets, which may help to identify the nearest potentially habitable worlds.

We seek to quantify the fidelity with which modern population syntheses reproduce observations in view of their use as predictive tools. We compared synthetic populations from the Generation 3 Bern Model of Planet Formation and Evolution (core accretion, solar-type host stars) and the HARPS/Coralie radial velocity sample. We biased the synthetic planet population according to the completeness of the observed data and performed quantitative statistical comparisons and systematically identified agreements and differences. Our nominal population reproduces many of the main features of the HARPS planets: two main groups of planets (close-in sub-Neptunes and distant giants), a bimodal mass function with a less populated `desert', an observed mean multiplicity of about 1.6, and several key correlations. The remaining discrepancies point to areas that are not fully captured in the model. For instance, we find that the synthetic population has 1) in absolute terms too many planets by ~70%, 2) a `desert' that is too deep by ~60%, 3) a relative excess of giant planets by ~40%, 4) planet eccentricities that are on average too low by a factor of about two (median of 0.07 versus 0.15), and 5) a metallicity effect that is too weak. Finally, the synthetic planets are overall too close to the star compared to the HARPS sample. The differences allowed us to find model parameters that better reproduce the observed planet masses, for which we computed additional synthetic populations. We find that physical processes appear to be missing and that planets may originate on wider orbits than our model predicts. Mechanisms leading to higher eccentricities and slower disc-limited gas accretion also seem necessary. We advocate that theoretical models should make a quantitative comparison between the many current and future large surveys to better understand the origins of planetary systems. (Abridged.)

The Habitable Worlds Observatory (HWO) aims to telescopically constrain the frequency and abundance of biospheres in the solar neighborhood. Origin-of-life theories vary in their predictions for the environmental requirements and the expected frequency of abiogenesis, meaning that constraints on the frequency and distribution of life on exoplanets from HWO can in principle directly test theories of abiogenesis. We categorize origin-of-life theories into three broad classes and discuss how HWO could potentially test them. Nondetection of biology on a large sample of habitable planets would provide prior-independent evidence in favor of the class of abiogenesis theory which holds that the origin of life is a contingent, vanishingly unlikely event, whereas detection of event a single biosphere would falsify this class of theories. Correlations of candidate biospheres with planetary parameters such as UV irradiation, the presence of oceans, and the presence of continents can test specific origin-of-life theories. Simulated surveys with Bayesian analysis are required to quantify the ability of HWO to execute this science case. However, a clear theme from the limited such studies that have already been conducted is the need for large sample sizes (\\(\\gtrsim50\\) planets characterized) to provide meaningful constraints on abiogenesis theories, favoring a larger design sample for HWO.

Previous work concerning planet formation around low-mass stars has often been limited to large planets and individual systems. As current surveys routinely detect planets down to terrestrial size in these systems, a more holistic approach that reflects their diverse architectures is timely. Here, we investigate planet formation around low-mass stars and identify differences in the statistical distribution of planets. We compare the synthetic planet populations to observed exoplanets. We used the Generation III Bern model of planet formation and evolution to calculate synthetic populations varying the central star from solar-like stars to ultra-late M dwarfs. This model includes planetary migration, N-body interactions between embryos, accretion of planetesimals and gas, and long-term contraction and loss of the gaseous atmospheres. We find that temperate, Earth-sized planets are most frequent around early M dwarfs and more rare for solar-type stars and late M dwarfs. The planetary mass distribution does not linearly scale with the disk mass. The reason is the emergence of giant planets for M*>0.5 Msol, which leads to the ejection of smaller planets. For M*>0.3 Msol there is sufficient mass in the majority of systems to form Earth-like planets, leading to a similar amount of Exo-Earths going from M to G dwarfs. In contrast, the number of super-Earths and larger planets increases monotonically with stellar mass. We further identify a regime of disk parameters that reproduces observed M-dwarf systems such as TRAPPIST-1. However, giant planets around late M dwarfs such as GJ 3512b only form when type I migration is substantially reduced. We quantify the stellar mass dependence of multi-planet systems using global simulations of planet formation and evolution. The results compare well to current observational data and predicts trends that can be tested with future observations.

Will future direct imaging missions such as NASA's upcoming Habitable Worlds Observatory (HWO) be able to understand Earth-sized planets as a population? In this study, we simulate the ability of space-based coronagraphy missions to uncover trends in planetary albedo as a function of instellation, and potentially constrain the boundaries of the habitable zone. We adapt the Bioverse statistical comparative planetology framework to simulate the scientific output of possible designs for HWO. With this tool, we generate a synthetic planetary population with injected population-level trends in albedo and simulate the observability of planets. We then determine the statistical power to which these trends can be recovered as a function of the strength of the injected trend and the sample size of Earth-sized planets in the habitable zone (exoEarths). The strongest trends in albedo require a sample size of roughly 25-30 exoEarths to recover with high confidence. However, for weaker albedo trends, the required number of planets increases rapidly. If a mission is designed to meet the Decadal Survey's requirement of 25 exoEarths, it would be able to recover very strong trends in albedo associated with the habitable zone, but would struggle to confidently detect weaker trends. We explore multiple strategies to increase one's ability to recover weak trends, such as reducing the uncertainties in observables, incorporating additional observables such as planet colors, and obtaining direct constraints on planetary albedo from full spectral retrievals.

Planet formation is sensitive to the conditions in protoplanetary disks, for which scaling laws as a function of stellar mass are known. We aim to test whether the observed population of planets around low-mass stars can be explained by these trends, or if separate formation channels are needed. We address this question by confronting a state-of-the-art planet population synthesis model with a sample of planets around M dwarfs observed by the HARPS and CARMENES radial velocity (RV) surveys. To account for detection biases, we performed injection and retrieval experiments on the actual RV data to produce synthetic observations of planets that we simulated following the core accretion paradigm. These simulations robustly yield the previously reported high occurrence of rocky planets around M dwarfs and generally agree with their planetary mass function. In contrast, our simulations cannot reproduce a population of giant planets around stars less massive than 0.5 solar masses. This potentially indicates an alternative formation channel for giant planets around the least massive stars that cannot be explained with current core accretion theories. We further find a stellar mass dependency in the detection rate of short-period planets. A lack of close-in planets around the earlier-type stars (\\(M_ 0.4\\, M_\\)) in our sample remains unexplained by our model and indicates dissimilar planet migration barriers in disks of different spectral subtypes. Both discrepancies can be attributed to gaps in our understanding of planet migration in nascent M dwarf systems. They underline the different conditions around young stars of different spectral subtypes, and the importance of taking these differences into account when studying planet formation.

The Habitable Worlds Observatory (HWO) aims to characterize habitable exoplanets in search of signs of life. However, detectable life may be rare, either because abiogenesis is intrinsically contingent and unlikely, or because biospheres may efficiently recycle their products. Here, we explore the potential of HWO to test theories of life in the universe even if detectable life is rare by searching for \"prebiosignature gases\". Prebiosignatures gases are gases whose detection constrains theories of the evolution of prebiotic (habitable but uninhabited) planets, thereby testing theories of abiogenesis and guiding laboratory investigations of the origin of life. We catalog 5 theories of prebiotic environments that are potentially testable by HWO, identify their observational tests, and rank them by perceived detection plausibility. The prebiosignature paradigm is novel and potentially compelling, but considerable work is required to mature it and assess its practical relevance for HWO, especially simulated spectral observation and retrieval studies. However, consideration of the absorption properties of prebiosignature observables alone reveals that coverage at NUV wavelengths (200-400 nm) will be required to effectively realize a prebiosignature science case for HWO, supporting the argument for UV capabilities for HWO.

We present a joint analysis of TTVs and Doppler data for the transiting exoplanet system TOI-4504. TOI-4504 c is a warm Jupiter-mass planet that exhibits the largest known transit timing variations (TTVs), with a peak-to-node amplitude of \\(\\sim\\) 2 days, the largest value ever observed, and a super-period of \\(\\sim\\) 930 d. TOI-4504 b and c were identified in public TESS data, while the TTVs observed in TOI-4504 c, together with radial velocity (RV) data collected with FEROS, allowed us to uncover a third, non-transiting planet in this system, TOI-4504 d. We were able to detect transits of TOI-4504 b in the TESS data with a period of 2.4261\\(\\pm 0.0001\\) days and derive a radius of 2.69\\(\\pm 0.19\\) R\\(_{\\oplus}\\). The RV scatter of TOI-4504 was too large to constrain the mass of TOI-4504 b, but the RV signals of TOI-4504 c \\& d were sufficiently large to measure their masses. The TTV+RV dynamical model we apply confirms TOI-4504 c as a warm Jupiter planet with an osculating period of 82.54\\(\\pm 0.02\\) d, mass of 3.77\\(\\pm 0.18\\) M\\(_{\\rm J}\\) and a radius of 0.99\\(\\pm 0.05\\) R\\(_{\\rm J}\\), while the non-transiting planet TOI-4504 d, has an orbital period of 40.56\\(\\pm 0.04\\) days and mass of 1.42\\(_{-0.06}^{+0.07}\\) M\\(_{\\rm J}\\). We present the discovery of a system with three exoplanets: a hot sub-Neptune and two warm Jupiter planets. The gas giant pair is stable and likely locked in a first-order 2:1 mean-motion resonance (MMR). The TOI-4504 system is an important addition to MMR pairs, whose increasing occurrence supports a smooth migration into a resonant configuration during the protoplanetary disk phase.