Articles de revues : « Habitabilité (astronomie) »

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Sandora, McCullen, Vladimir Airapetian, Luke Barnes et Geraint F. Lewis. « Multiverse Predictions for Habitability : Stellar and Atmospheric Habitability ». Universe 9, n^o 1 (21 décembre 2022) : 4. http://dx.doi.org/10.3390/universe9010004.

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Stellar activity and planetary atmospheric properties have the potential to strongly influence habitability. To date, neither have been adequately studied in the multiverse context, so there has been no assessment of how these effects impact the probabilities of observing our fundamental constants. Here, we consider the effects of solar wind, mass loss, and extreme ultra-violet (XUV) flux on planetary atmospheres, how these effects scale with fundamental constants, and how this affects the likelihood of our observations. We determine the minimum atmospheric mass that can withstand erosion, maintain liquid surface water, and buffer diurnal temperature changes. We consider two plausible sources of Earth’s atmosphere, as well as the notion that only initially slowly rotating stars are habitable, and find that all are equally compatible with the multiverse. We consider whether planetary magnetic fields are necessary for habitability, and find five boundaries in parameter space where magnetic fields are precluded. We find that if an Earth-like carbon-to-oxygen ratio is required for life, atmospheric effects do not have much of an impact on multiverse calculations. If significantly different carbon-to-oxygen ratios are compatible with life, magnetic fields must not be essential for life, and planet atmosphere must not scale with stellar nitrogen abundance, or else the multiverse would be ruled out to a high degree of confidence.

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Kite, Edwin S., et Eric B. Ford. « Habitability of Exoplanet Waterworlds ». Astrophysical Journal 864, n^o 1 (31 août 2018) : 75. http://dx.doi.org/10.3847/1538-4357/aad6e0.

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Gobat, R., et S. E. Hong. « Evolution of galaxy habitability ». Astronomy & ; Astrophysics 592 (août 2016) : A96. http://dx.doi.org/10.1051/0004-6361/201628834.

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Dartnell, Lewis. « Biological constraints on habitability ». Astronomy & ; Geophysics 52, n^o 1 (19 janvier 2011) : 1.25–1.28. http://dx.doi.org/10.1111/j.1468-4004.2011.52125.x.

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Sandora, McCullen, Vladimir Airapetian, Luke Barnes et Geraint F. Lewis. « Multiverse Predictions for Habitability : Planetary Characteristics ». Universe 9, n^o 1 (21 décembre 2022) : 2. http://dx.doi.org/10.3390/universe9010002.

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Recent detections of potentially habitable exoplanets around sunlike stars demand increased exploration of the physical conditions that can sustain life, by whatever methods available. Insight into these conditions can be gained by considering the multiverse hypothesis; in a multiverse setting, the probability of living in our universe depends on assumptions made about the factors affecting habitability. Various proposed habitability criteria can be systematically considered to rate each on the basis of their compatibility with the multiverse, generating predictions which can both guide expectations for life’s occurrence and test the multiverse hypothesis. Here, we evaluate several aspects of planetary habitability, and show that the multiverse does indeed induce strong preferences among them. We find that the notion that a large moon is necessary for habitability is untenable in the multiverse scenario, as in the majority of parameter space, moons are not necessary to maintain stable obliquity. Further, we consider various proposed mechanisms for water delivery to the early Earth, including delivery from asteroids, both during giant planet formation and a grand tack, delivery from comets, and oxidation of a primary atmosphere by a magma ocean. We find that, depending on assumptions for how habitability depends on water content, some of these proposed mechanisms are disfavored in the multiverse scenario by Bayes factors of up to several hundred.

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Lenardic, A., et J. Seales. « Habitability : a process versus a state variable framework with observational tests and theoretical implications ». International Journal of Astrobiology 20, n^o 2 (21 janvier 2021) : 125–32. http://dx.doi.org/10.1017/s1473550420000415.

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The term habitable is used to describe planets that can harbour life. Debate exists as to specific conditions that allow for habitability but the use of the term as a planetary variable has become ubiquitous. This paper poses a meta-level question: What type of variable is habitability? Is it akin to temperature, in that it is something that characterizes a planet, or is something that flows through a planet, akin to heat? That is, is habitability a state or a process variable? Forth coming observations can be used to discriminate between these end-member hypotheses. Each has different implications for the factors that lead to differences between planets (e.g. the differences between Earth and Venus). Observational tests can proceed independent of any new modelling of planetary habitability. However, the viability of habitability as a process can influence future modelling. We discuss a specific modelling framework based on anticipating observations that can discriminate between different views of habitability.

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Rodríguez-López, Lien, Rolando Cardenas, Oscar Parra, Lisdelys González-Rodríguez, Osmel Martin et Roberto Urrutia. « On the quantification of habitability : merging the astrobiological and ecological schools ». International Journal of Astrobiology 18, n^o 05 (30 août 2018) : 412–15. http://dx.doi.org/10.1017/s1473550418000344.

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AbstractIn this paper, we connect ideas of the astrobiological and ecological schools to quantify habitability. We show how habitability indexes, devised using the astrobiologically inspired Quantitative Habitability Theory (QHT), can be embedded into ecological models of trophic levels. In particular, we address the problem of spatial-temporal scales. It turns out that the versatility of QHT allows to treat spatial and temporal scales typical of ecological studies. As a habitability index, we propose a new version of our Aquatic Primary Habitability, devised by some of us and formerly applied to saltwater ecosystems (both ocean and coastal) and now applied to freshwater. Although the aim of the paper is to outline the methodology rather than realism, initial steps for parameterization are considered for lakes of South-Central Chile.

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Rodríguez, Elio Quiroga. « Frank Drake is Alive ! (Rethinking the Drake Equation for the Search For Biological Life) ». Journal of the British Interplanetary Society 77, n^o 4 (12 septembre 2024) : 114–18. http://dx.doi.org/10.59332/jbis-077-04-0114.

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In 1961, astronomer Frank Drake formulated the Drake Equation as a cornerstone for scientific discourse regarding the prevalence of communicative extraterrestrial civilizations within the Milky Way galaxy. This equation, often referred to as the “Classic Drake Equation”, outlines the key factors influencing the number of potential civilizations with which we might establish communication. This article submerges into the Drake Equation and proposes a simplified version focused on the broader detection of extraterrestrial non-intelligent life. The established terms of the equation, such as the rate of stellar formation, the fraction of stars harboring planetary systems, and the probability of such systems containing habitable planets, are re-examined and discussed. Additionally, a reevaluation of other factors is presented. Based on this revised framework, various scenarios are explored. As our technological capabilities continue to advance, the detection of biosignatures on exoplanets (incorporated into the suggested new version of the equation) is anticipated to offer insights into the search for life beyond Earth. Keywords: Drake Equation, Extraterrestrial Life, Exoplanetology, Habitability, Biomarkers, Communicative Civilizations

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Shevchenko, Ivan I. « Habitability Properties of Circumbinary Planets ». Astronomical Journal 153, n^o 6 (1 juin 2017) : 273. http://dx.doi.org/10.3847/1538-3881/aa71b2.

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Valencia, Diana, Vivian Yun Yan Tan et Zachary Zajac. « Habitability from Tidally Induced Tectonics ». Astrophysical Journal 857, n^o 2 (20 avril 2018) : 106. http://dx.doi.org/10.3847/1538-4357/aab767.

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Đošović, Vladimir, Branislav Vukotić et Milan M. Ćirković. « Advanced aspects of Galactic habitability ». Astronomy & ; Astrophysics 625 (mai 2019) : A98. http://dx.doi.org/10.1051/0004-6361/201834588.

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Context. Astrobiological evolution of the Milky Way (or the shape of its “astrobiological landscape”) has emerged as a key research topic in recent years. In order to build precise, quantitative models of the Galactic habitability, we need to account for two opposing tendencies of life and intelligence in the most general context: the tendency to spread to all available ecological niches (conventionally dubbed “colonization”) and the tendency to succumb to various types of existential catastrophes (“catastrophism”). These evolutionary tendencies have become objects of study in fields such as ecology, macroevolution, risk analysis, and futures studies, though a serious astrobiological treatment has so far been lacking. Aims. Our aim is to numerically investigate the dynamics of opposed processes of expansion (panspermia, colonization) and extinction (catastrophic mechanisms) of life in the Galaxy. Methods. We employed a new type of numerical simulation based on 1D probabilistic cellular automaton with very high temporal resolution, in order to study astrobiological dynamics. Results. While the largest part of the examined parameter space shows very low habitability values, as expected, the remaining part has some observationally appealing features that imply, among other things, a reduction in the amount of fine-tuning necessary for resolving the Fermi paradox. Conclusions. Advanced aspects of Galactic habitability are amenable to precision studies using massive parallel computer simulations. There are regions of the parameter space that correspond to a quasi-stationary state satisfying observable constraints and possessing viable SETI targets.

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Barnes, Rory, Victoria S. Meadows et Nicole Evans. « COMPARATIVE HABITABILITY OF TRANSITING EXOPLANETS ». Astrophysical Journal 814, n^o 2 (19 novembre 2015) : 91. http://dx.doi.org/10.1088/0004-637x/814/2/91.

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Barnes, Rory, Brian Jackson, Richard Greenberg et Sean N. Raymond. « TIDAL LIMITS TO PLANETARY HABITABILITY ». Astrophysical Journal 700, n^o 1 (30 juin 2009) : L30—L33. http://dx.doi.org/10.1088/0004-637x/700/1/l30.

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Javaux, Emmanuelle J., et Véronique Dehant. « Habitability : from stars to cells ». Astronomy and Astrophysics Review 18, n^o 3 (8 juin 2010) : 383–416. http://dx.doi.org/10.1007/s00159-010-0030-4.

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Van Laerhoven, C., R. Barnes et R. Greenberg. « Tides, planetary companions, and habitability : habitability in the habitable zone of low-mass stars ». Monthly Notices of the Royal Astronomical Society 441, n^o 3 (12 mai 2014) : 1888–98. http://dx.doi.org/10.1093/mnras/stu685.

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Abrevaya, Ximena C., Martin Leitzinger, Oscar J. Oppezzo, Petra Odert, G. Juan M. Luna, Manish Patel, Ana F. Forte-Giacobone et Arnold Hanslmeier. « Towards astrobiological experimental approaches to study planetary UV surface environments ». Proceedings of the International Astronomical Union 14, S345 (août 2018) : 222–26. http://dx.doi.org/10.1017/s1743921319002205.

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AbstractThe stellar ultraviolet radiation (UVR) has been studied in the last decade and has been found to be an important factor to determine the habitability of planetary surfaces. It is known that UVR can be a constraint for life. However, most of the studies of UVR and habitability have missed some fundamental aspects: i) Accurate estimation of the planetary atmospheric attenuation, ii) The biological inferences used to represent the impact of the stellar UVR on life are theoretical and based on the action spectrum (for DNA or microorganisms) or considering parameters as the “lethal dose” obtained from non-astrobiological experiments. Therefore, the conclusions reached by previous studies about the UVR habitability of planetary bodies may be inaccurate. In this work, we propose how to address these studies in a more accurate way through an interdisciplinary approach that combines astrophysics, microbiology, and photobiology and by the use of specially designed laboratory experiments.

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Lobo, Ana H., Aomawa L. Shields, Igor Z. Palubski et Eric Wolf. « Terminator Habitability : The Case for Limited Water Availability on M-dwarf Planets ». Astrophysical Journal 945, n^o 2 (1 mars 2023) : 161. http://dx.doi.org/10.3847/1538-4357/aca970.

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Abstract Rocky planets orbiting M-dwarf stars are among the most promising and abundant astronomical targets for detecting habitable climates. Planets in the M-dwarf habitable zone are likely synchronously rotating, such that we expect significant day–night temperature differences and potentially limited fractional habitability. Previous studies have focused on scenarios where fractional habitability is confined to the substellar or “eye” region, but in this paper we explore the possibility of planets with terminator habitability, defined by the existence of a habitable band at the transition between a scorching dayside and a glacial nightside. Using a global climate model, we show that for water-limited planets it is possible to have scorching temperatures in the “eye” and freezing temperatures on the nightside, while maintaining a temperate climate in the terminator region, due to reduced atmospheric energy transport. On water-rich planets, however, increasing the stellar flux leads to increased atmospheric energy transport and a reduction in day–night temperature differences, such that the terminator does not remain habitable once the dayside temperatures approach runaway or moist greenhouse limits. We also show that while water-abundant simulations may result in larger fractional habitability, they are vulnerable to water loss through cold trapping on the nightside surface or atmospheric water vapor escape, suggesting that even if planets were formed with abundant water, their climates could become water-limited and subject to terminator habitability.

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Sandora, McCullen, Vladimir Airapetian, Luke Barnes, Geraint F. Lewis et Ileana Pérez-Rodríguez. « Multiverse Predictions for Habitability : Element Abundances ». Universe 8, n^o 12 (7 décembre 2022) : 651. http://dx.doi.org/10.3390/universe8120651.

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We investigate the dependence of elemental abundances on physical constants, and the implications this has for the distribution of complex life for various proposed habitability criteria. We consider three main sources of abundance variation: differing supernova rates, alpha burning in massive stars, and isotopic stability, and how each affects the metal-to-rock ratio and the abundances of carbon, oxygen, nitrogen, phosphorus, sulfur, silicon, magnesium, and iron. Our analysis leads to several predictions for which habitability criteria are correct by determining which ones make our observations of the physical constants, as well as a few other observed features of our universe, most likely. Our results indicate that carbon-rich or carbon-poor planets are uninhabitable, slightly magnesium-rich planets are habitable, and life does not depend on nitrogen abundance too sensitively. We also find suggestive but inconclusive evidence that metal-rich planets and phosphorus-poor planets are habitable. These predictions can then be checked by probing regions of our universe that closely resemble normal environments in other universes. If any of these predictions are found to be wrong, the multiverse scenario would predict that the majority of observers are born in universes differing substantially from ours, and so can be ruled out, to varying degrees of statistical significance.

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Becker, Juliette, Darryl Z. Seligman, Fred C. Adams et Marshall J. Styczinski. « The Influence of Tidal Heating on the Habitability of Planets Orbiting White Dwarfs ». Astrophysical Journal Letters 945, n^o 2 (1 mars 2023) : L24. http://dx.doi.org/10.3847/2041-8213/acbe44.

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Abstract In recent years, there have been a growing number of observations indicating the presence of rocky material in short-period orbits around white dwarfs. In this Letter, we revisit the prospects for habitability around these post-main-sequence star systems. In addition to the typically considered radiative input luminosity, potentially habitable planets around white dwarfs are also subjected to significant tidal heating. The combination of these two heating sources can, for a narrow range of planetary properties and orbital parameters, continuously maintain surface temperatures amenable for habitability for planets around white dwarfs over timescales up to 10 Gyr. We show that for a specific locus of orbital parameter space, tidal heating can substantially extend the timescale of continuous habitability for a planet around a white dwarf.

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Bahraminasr, Majid, S. Javad Jafarzadeh, Fatemeh Montazeri, Atila Poro et Soroush Sarabi. « Evaluating the effect of four unknown parameters included in a latitudinal energy balance model on the habitability of exoplanets ». Open Astronomy 29, n^o 1 (31 décembre 2020) : 231–50. http://dx.doi.org/10.1515/astro-2020-0021.

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AbstractAmong different models for determining the habitable zone (HZ) around a star, a Latitudinal Energy Balance Model (LEBM) is very beneficial due to its parametricity which keeps a good balance between complexity and simulation time. This flexibility makes the LEBM an excellent tool to assess the impact of some key physical parameters on the temperature and the habitability of a planet. Among different physical parameters, some of them, up until now, cannot be determined by any method such as the planet’s spin obliquity, diurnal period, ocean-land ratio, and pressure level. Here we apply this model to study the effect of these unknown parameters on the habitability of three exoplanets located in the inner, outer, and middle of their optimistic HZ. Among the examined parameters, the impact of pressure is more straightforward. It has a nearly direct relation with temperature and also with the habitability in the case of a cold planet. The effect of other parameters is discussed with details. To quantify the impact of all these unknown parameters we utilize a statistical interface which provides us with the conditional probability on habitability status of each planet.

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Guinan, Edward F., Scott G. Engle, Trisha Mizusawa, George P. McCook, A. Wolfe et Jeffrey Coughlin. « The “Living with a Red Dwarf” program : XUV radiation and plasma environments of hosted planets and impacts on habitability ». Proceedings of the International Astronomical Union 5, H15 (novembre 2009) : 703. http://dx.doi.org/10.1017/s1743921310011051.

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von Bloh, W., K. J. Kossacki, S. Franck et C. Bounama. « Diurnal Habitability of Frozen Worlds ». Earth, Moon, and Planets 106, n^o 1 (27 octobre 2009) : 15–26. http://dx.doi.org/10.1007/s11038-009-9343-6.

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Saha, Snehanshu, Nithin Nagaraj, Archana Mathur, Rahul Yedida et Sneha H R. « Evolution of novel activation functions in neural network training for astronomy data : habitability classification of exoplanets ». European Physical Journal Special Topics 229, n^o 16 (novembre 2020) : 2629–738. http://dx.doi.org/10.1140/epjst/e2020-000098-9.

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Hooper, Dan, et Jason H. Steffen. « Dark matter and the habitability of planets ». Journal of Cosmology and Astroparticle Physics 2012, n^o 07 (23 juillet 2012) : 046. http://dx.doi.org/10.1088/1475-7516/2012/07/046.

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Chen, Ruixuan E., Jonathan H. Jiang, Philip E. Rosen, Kristen A. Fahy et Yanbei Chen. « Exoplanets around Red Giants : Distribution and Habitability ». Galaxies 11, n^o 6 (16 novembre 2023) : 112. http://dx.doi.org/10.3390/galaxies11060112.

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As the search for exoplanets continues, more are being discovered orbiting Red Giant stars. We use current data from the NASA Exoplanet Archive to investigate planet distribution around Red Giant stars and their presence in the host’s habitable zone. As well, we explore the distribution of planet mass and orbital semi major axis for evolved stars with increasing stellar radii. From the distance distribution of the planets, we found evidence of engulfment during the post-Main Sequence evolution of the star. We found 9 Red Giant-hosted exoplanets, and 21 Subgiant-hosted exoplanets to be in the optimistically calculated habitable zone, 5 and 17 of which are in a more conservatively calculated habitable zone. All the planets detected within their habitable zone orbit stars that are in early stages of evolution. We believe that with more powerful instrumentation, more habitable planets may be found around stars that are in later stages of evolution.

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Madhusudhan, Nikku, Anjali A. A. Piette et Savvas Constantinou. « Habitability and Biosignatures of Hycean Worlds ». Astrophysical Journal 918, n^o 1 (26 août 2021) : 1. http://dx.doi.org/10.3847/1538-4357/abfd9c.

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Kane, Stephen R., et Sarah J. Deveny. « Habitability in the Omega Centauri Cluster ». Astrophysical Journal 864, n^o 2 (5 septembre 2018) : 115. http://dx.doi.org/10.3847/1538-4357/aad802.

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Whitmire, Daniel P. « The habitability of large elliptical galaxies ». Monthly Notices of the Royal Astronomical Society 494, n^o 2 (13 avril 2020) : 3048–52. http://dx.doi.org/10.1093/mnras/staa957.

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ABSTRACT Based on numbers of stars, supernova rates, and metallicity, a prior study concluded that large elliptical galaxies contain up to 10 000 times more habitable planets than the Milky Way and are thus the ‘cradles of life’. Using the results of their model and taking into account galactic number distributions and supernova rates, I argue here that this result constitutes a violation of the principle of mediocrity as applied to the reference class of all extant technological species. Assuming that we are a typical technological species in the attribute of inhabiting a relatively large disc-dominated galaxy, I outline two hypotheses that could significantly limit the habitability of large elliptical galaxies: (1) massive galactic sterilization events associated with quasar/active galactic nucleus activity and starburst supernovae that occurred when the antecedents of today’s large elliptical galaxies were much more compact; and (2) the probability of habitable planet formation in large elliptical galaxies may be small since a disproportionately larger number of gaseous planets are expected to form as a result of the generally higher metallicity in large elliptical galaxies. Consequently, fewer habitable planets will accrete if the gaseous planets' inward migrations are sufficiently slow. The sterilization events of hypothesis (1) occurred at earlier epochs ($z$ ≥ 1) and so they must be effectively permanent, implying two possible scenarios regarding the origin and evolution of life. In connection with one of these scenarios, independent applications of the principle of mediocrity suggest that M-dwarf stars are not significant hosts of technological life.

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Bloh, W. Von, C. Bounama et S. Franck. « Dynamic Habitability Of Extrasolar Planetary Systems ». Celestial Mechanics and Dynamical Astronomy 92, n^o 1-3 (avril 2005) : 287–300. http://dx.doi.org/10.1007/s10569-005-0005-3.

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Fishbaugh, Kathryn E., David J. Des Marais, Oleg Korablev, Philippe Lognonne et François Raulin. « Introduction : A Multidisciplinary Approach to Habitability ». Space Science Reviews 129, n^o 1-3 (mars 2007) : 1–5. http://dx.doi.org/10.1007/s11214-007-9208-0.

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Kokaia, Giorgi, Melvyn B. Davies et Alexander J. Mustill. « Resilient habitability of nearby exoplanet systems ». Monthly Notices of the Royal Astronomical Society 492, n^o 1 (9 décembre 2019) : 352–68. http://dx.doi.org/10.1093/mnras/stz3408.

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ABSTRACT We investigate the possibility of finding Earth-like planets in the habitable zone of 34 nearby FGK-dwarfs, each known to host one giant planet exterior to their habitable zone detected by RV. First we simulate the dynamics of the planetary systems in their present day configurations and determine the fraction of stable planetary orbits within their habitable zones. Then, we postulate that the eccentricity of the giant planet is a result of an instability in their past during which one or more other planets were ejected from the system. We simulate these scenarios and investigate whether planets orbiting in the habitable zone survive the instability. Explicitly we determine the fraction of test particles, originally found in the habitable zone, which remain in the habitable zone today. We label this fraction the resilient habitability of a system. We find that for most systems the probability of planets existing [or surviving] on stable orbits in the habitable zone becomes significantly smaller when we include a phase of instability in their history. We present a list of candidate systems with high resilient habitability for future observations. These are: HD 95872, HD 154345, HD 102843, HD 25015, GJ 328, HD 6718, and HD 150706. The known planets in the last two systems have large observational uncertainties on their eccentricities, which propagate into large uncertainties on their resilient habitability. Further observational constraints of these two eccentricities will allow us to better constrain the survivability of Earth-like planets in these systems.

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Stevenson, David J. « Commentary : The habitability mantra : Hunting the Snark ». Physics Today 71, n^o 11 (novembre 2018) : 10–12. http://dx.doi.org/10.1063/pt.3.4054.

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Spinelli, Riccardo, et Giancarlo Ghirlanda. « The Impact of GRBs on Exoplanetary Habitability ». Universe 9, n^o 2 (17 janvier 2023) : 60. http://dx.doi.org/10.3390/universe9020060.

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Can high-energy transient events affect life on a planet? We provide a review of the works that have tried to answer this question. It is argued that that gamma ray bursts, specifically those of the long class, are among the most dangerous astrophysical sources for biotic life and may exert evolutionary pressure on possible life forms in the universe. Their radiation can be directly lethal for biota or induce extinction by removing most of the protective atmospheric ozone layer on terrestrial planets. Since the rate of long gamma ray bursts is proportional to the birth rate of stars but is reduced in metal rich regions, the evolution of the “safest place” to live in our galaxy depended on the past 12 billion years of evolution of the star formation rate and relative metal pollution of the interstellar medium. Until 6 billion years ago, the outskirts of the galaxy were the safest places to live, despite the relatively low density of terrestrial planets. In the last 5 billion years, regions between 2 and 8 kiloparsecs from the center, featuring a higher density of terrestrial planets, gradually became the best places for safe biotic life growth.

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Cockell, Charles S., et Frances Westall. « A postulate to assess ‘habitability’ ». International Journal of Astrobiology 3, n^o 2 (avril 2004) : 157–63. http://dx.doi.org/10.1017/s1473550404002083.

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One principal challenge in biology is defining a postulate by which the habitability of other planets can be assessed. Current assessments suffer from two potential weaknesses. With respect to other planets, either assumptions are made about the physical and chemical conditions of environments that err on the side of biological optimism without empirical constraint by spacecraft observations or novel physiologies of microorganisms are invented to fit extraterrestrial environmental conditions with no demonstrated microbiological counterparts on Earth. Attempts to assess the habitability of the early Earth suffer from similar problems. We discuss the following postulate: ‘the proposition that a planet is or was habitable requires that the physiological requirements of microorganisms on Earth known at the time of assessment match the empirically determined combined physical and chemical conditions in the extraterrestrial or early Earth environment being assessed’ as a means of evaluating ‘habitability’. We use as tests for our postulate the early Earth and the cloud deck of Venus (a habitat that has been a source of optimistic debate for forty years). We conclude that, although the early Earth was habitable, Venus is a dead world.

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Pacetti, E., A. Balbi, M. Lingam, F. Tombesi et E. Perlman. « The impact of tidal disruption events on galactic habitability ». Monthly Notices of the Royal Astronomical Society 498, n^o 3 (21 août 2020) : 3153–57. http://dx.doi.org/10.1093/mnras/staa2535.

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ABSTRACT Tidal disruption events (TDEs) are characterized by the emission of a short burst of high-energy radiation. We analyse the cumulative impact of TDEs on galactic habitability using the Milky Way as a proxy. We show that X-rays and extreme ultraviolet radiation emitted during TDEs can cause hydrodynamic escape and instigate biological damage. By taking the appropriate variables into consideration, such as the efficiency of atmospheric escape and distance from the Galactic centre, we demonstrate that the impact of TDEs on galactic habitability is comparable to that of active galactic nuclei. In particular, we show that planets within distances of ∼0.1–1 kpc could lose Earth-like atmospheres over the age of the Earth, and that some of them might be subject to biological damage once every ≳ 104 yr. We conclude by highlighting potential ramifications of TDEs and argue that they should be factored into future analyses of inner galactic habitability.

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Ahlers, John P., Emeline F. Fromont, Ravi Kopparappu, P. Wilson Cauley et Jacob Haqq-Misra. « The Habitable Zones of Rapidly Rotating Main Sequence A/F Stars ». Astrophysical Journal 928, n^o 1 (1 mars 2022) : 35. http://dx.doi.org/10.3847/1538-4357/ac5596.

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Abstract We investigate how rapid stellar rotation commonly seen in A/F stars can influence planet habitability. Specifically, we model how rapid rotation influences a planet’s irradiation and determine the location of the habitable zone for stars in the mass range 1.3 M ⊙ ≤ M ⋆ ≤ 2.2 M ⊙. Rapid stellar rotation can dramatically change a star’s luminosity and spectral energy distribution, and therefore can affect the habitability of any surrounding planets. Stars of mass M ⋆ ≳ 1.3 M ⊙ commonly rotate near their breakup speeds, which causes two effects relevant to planet habitability. First, these stars flatten into oblate spheroids with shorter polar radii and elongated equatorial radii. Second, rapid rotation induces a pole-to-equator temperature gradient on the surface of these stars. Using a 1D climate model, we calculate the inner and outer edges of the habitable zone of well-known rapid rotators and average theoretical stars in our stellar mass range. We find that, in general, rapid rotation causes the habitable zone to reside closer in than for a nonrotating equivalent star. We also find that gravity darkening dramatically reduces stellar UV emission, which combats the common assumption that high-mass stars emit too much UV light for habitable worlds. Overall, we determine that rapid stellar rotation has important consequences for the overall habitability of a system and must be accounted for both when modeling exoplanet environments and in observation of planets around high-mass stars.

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von Bloh, W., C. Bounama, M. Cuntz et S. Franck. « Habitability of super-Earths : Gliese 581c & ; 581d ». Proceedings of the International Astronomical Union 3, S249 (octobre 2007) : 503–6. http://dx.doi.org/10.1017/s1743921308017031.

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AbstractThe unexpected diversity of exoplanets includes a growing number of super-Earth planets, i.e., exoplanets with masses smaller than 10 Earth masses. Unlike the larger exoplanets previously found, these smaller planets are more likely to have similar chemical and mineralogical composition to the Earth. We present a thermal evolution model for super-Earth planets to identify the sources and sinks of atmospheric carbon dioxide. The photosynthesis-sustaining habitable zone (pHZ) is determined by the limits of biological productivity on the planetary surface. We apply our model to calculate the habitability of the two super-Earths in the Gliese 581 system. The super-Earth Gl 581c is clearly outside the pHZ, while Gl 581d is at the outer edge of the pHZ. Therefore, it could at least harbor some primitive forms of life.

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Adams, Fred C., et Evan Grohs. « On the habitability of universes without stable deuterium ». Astroparticle Physics 91 (mai 2017) : 90–104. http://dx.doi.org/10.1016/j.astropartphys.2017.03.009.

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He, Feng, Aronne Merrelli, Tristan S. L’Ecuyer et Margaret C. Turnbull. « Climate Outcomes of Earth-similar Worlds as a Function of Obliquity and Rotation Rate ». Astrophysical Journal 933, n^o 1 (1 juillet 2022) : 62. http://dx.doi.org/10.3847/1538-4357/ac6951.

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Abstract A set of simulations with a 3D global climate model are performed to investigate the roles of obliquity and rotation period in the habitability of Earthlike exoplanets. The simulations cover the obliquity–rotation parameter space, from 0° to 90° in obliquity and 1–128 days in rotation period. The simulated global mean temperatures are warmest at 45° obliquity with fast rotations, due to the modification of the greenhouse effect from the spatial redistribution of clouds and water vapor. The slow-moving insolation–cloud mechanism, previously found in simulations with slow rotations and zero obliquity, also produces a cooling trend from intermediate obliquity to high obliquity, with the coldest climate occurring at 90° obliquity for all rotation periods. At low obliquities and fast rotation, persistent snow and sea ice can form, producing cooler temperatures. A Climate Habitability metric is defined, based on temperature and precipitation, which compares well with observations when applied to a simulation using Earth’s obliquity and rotation. Over a wider range of obliquity and rotation period, the Climate Habitability ranges from 10% to 70% of the terrestrial area. Overall, the simulated global mean surface temperature shows a much larger spread across the range of simulated rotation periods at 45° obliquity compared to 0° obliquity. Therefore, we conclude that 3D exoplanet simulations using intermediate obliquities (e.g., 45°) instead of 0° will reveal a wider range of possible climate conditions for specific orbital configurations. In addition, Earth’s climate habitability can increase by 25% if the obliquity increases from 23.°5 to 45°.

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Tuchow, Noah W., et Jason T. Wright. « The Abundance of Belatedly Habitable Planets and Ambiguities in Definitions of the Continuously Habitable Zone ». Astrophysical Journal 944, n^o 1 (1 février 2023) : 71. http://dx.doi.org/10.3847/1538-4357/acb054.

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Abstract A planet’s history dictates its current potential to host habitable conditions and life. The concept of the continuously habitable zone (CHZ) has been used to define the region around a star most likely to host planets with long-term habitability. However, definitions of the CHZ vary in the literature and often conflict with each other. Calculating the fraction of habitable zone planets in the CHZ as a function of stellar properties, we find that the quality of a star as a host for planets with long-term habitability and biosignatures depends strongly on the formulation of the CHZ used. For instance, older M stars are either excellent or suboptimal hosts for CHZ planets, depending on whether one’s definition of habitability prioritizes the total time spent in the habitable zone or the continuity of habitable conditions from the delivery of volatiles to its current age. In this study, we focus on belatedly habitable zone (BHZ) planets, i.e., planets that enter the habitable zone after formation due to the evolution of their host star. We find that between ∼29% and 74% of planets in the habitable zone belong to this class of BHZ planets, depending on the timescale for the delivery of volatiles. Whether these planets can retain their volatiles and support habitable conditions is unclear. Since BHZ planets comprise a large portion of the planets we expect to survey for biosignatures with future missions, the open question of their habitability is an important factor for mission design, survey strategies, and the interpretation of results.

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Yamashiki, Yosuke A., Hiroyuki Maehara, Vladimir Airapetian, Yuta Notsu, Tatsuhiko Sato, Shota Notsu, Ryusuke Kuroki et al. « Impact of Stellar Superflares on Planetary Habitability ». Astrophysical Journal 881, n^o 2 (20 août 2019) : 114. http://dx.doi.org/10.3847/1538-4357/ab2a71.

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Wandel, Amri, et Lev Tal-Or. « On the Habitability of Teegarden’s Star Planets ». Astrophysical Journal 880, n^o 2 (30 juillet 2019) : L21. http://dx.doi.org/10.3847/2041-8213/ab2df7.

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Tjoa, J. N. K. Y., M. Mueller et F. F. S. van der Tak. « The subsurface habitability of small, icy exomoons ». Astronomy & ; Astrophysics 636 (avril 2020) : A50. http://dx.doi.org/10.1051/0004-6361/201937035.

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Context. Assuming our Solar System as typical, exomoons may outnumber exoplanets. If their habitability fraction is similar, they would thus constitute the largest portion of habitable real estate in the Universe. Icy moons in our Solar System, such as Europa and Enceladus, have already been shown to possess liquid water, a prerequisite for life on Earth. Aims. We intend to investigate under what thermal and orbital circumstances small, icy moons may sustain subsurface oceans and thus be “subsurface habitable”. We pay specific attention to tidal heating, which may keep a moon liquid far beyond the conservative habitable zone. Methods. We made use of a phenomenological approach to tidal heating. We computed the orbit averaged flux from both stellar and planetary (both thermal and reflected stellar) illumination. We then calculated subsurface temperatures depending on illumination and thermal conduction to the surface through the ice shell and an insulating layer of regolith. We adopted a conduction only model, ignoring volcanism and ice shell convection as an outlet for internal heat. In doing so, we determined at which depth, if any, ice melts and a subsurface ocean forms. Results. We find an analytical expression between the moon’s physical and orbital characteristics and the melting depth. Since this expression directly relates icy moon observables to the melting depth, it allows us to swiftly put an upper limit on the melting depth for any given moon. We reproduce the existence of Enceladus’ subsurface ocean; we also find that the two largest moons of Uranus (Titania and Oberon) could well sustain them. Our model predicts that Rhea does not have liquid water. Conclusions. Habitable exomoon environments may be found across an exoplanetary system, largely irrespective of the distance to the host star. Small, icy subsurface habitable moons may exist anywhere beyond the snow line. This may, in future observations, expand the search area for extraterrestrial habitable environments beyond the circumstellar habitable zone.

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Stojković, N., B. Vukotić, N. Martinović, M. M. Ćirković et M. Micic. « Galactic habitability re-examined : indications of bimodality ». Monthly Notices of the Royal Astronomical Society 490, n^o 1 (9 septembre 2019) : 408–16. http://dx.doi.org/10.1093/mnras/stz2519.

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ABSTRACT The problem of the extent of habitable zones in different kinds of galaxies is one of the outstanding challenges for contemporary astrobiology. In the present study, we investigate habitability in a large sample of simulated galaxies from the illustris Project in order to at least roughly quantify the hospitality to life of different galactic types. The pioneering study of Dayal et al. is critically examined and some of its results are amended. In particular, we find a tentative evidence for a second mode of galactic habitability comprising metal-rich dwarfs similar to IC 225, LMC, or M32. The role of the galactic environment and the observation-selection effects is briefly discussed and prospects for further research on the topic outlined.

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Menou, Kristen, et Serge Tabachnik. « Dynamical Habitability of Known Extrasolar Planetary Systems ». Astrophysical Journal 583, n^o 1 (20 janvier 2003) : 473–88. http://dx.doi.org/10.1086/345359.

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Tosi, N., M. Godolt, B. Stracke, T. Ruedas, J. L. Grenfell, D. Höning, A. Nikolaou, A. C. Plesa, D. Breuer et T. Spohn. « The habitability of a stagnant-lid Earth ». Astronomy & ; Astrophysics 605 (septembre 2017) : A71. http://dx.doi.org/10.1051/0004-6361/201730728.

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Shields, Aomawa L., Sarah Ballard et John Asher Johnson. « The habitability of planets orbiting M-dwarf stars ». Physics Reports 663 (décembre 2016) : 1–38. http://dx.doi.org/10.1016/j.physrep.2016.10.003.

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Sandora, McCullen, Vladimir Airapetian, Luke Barnes, Geraint F. Lewis et Ileana Pérez-Rodríguez. « Multiverse Predictions for Habitability : Origin of Life Scenarios ». Universe 9, n^o 1 (9 janvier 2023) : 42. http://dx.doi.org/10.3390/universe9010042.

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If the origin of life is rare and sensitive to the local conditions at the site of its emergence, then, using the principle of mediocrity within a multiverse framework, we may expect to find ourselves in a universe that is better than usual at creating these necessary conditions. We use this reasoning to investigate several origin of life scenarios to determine whether they are compatible with the multiverse, including the prebiotic soup scenario, hydrothermal vents, delivery of prebiotic material from impacts, and panspermia. We find that most of these scenarios induce a preference toward weaker-gravity universes, and that panspermia and scenarios involving solar radiation or large impacts as a disequilibrium source are disfavored. Additionally, we show that several hypothesized habitability criteria which are disfavored when the origin of life is not taken into account become compatible with the multiverse, and that the emergence of life and emergence of intelligence cannot both be sensitive to disequilibrium production conditions.

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Zink, Jon K., et Bradley M. S. Hansen. « Accounting for multiplicity in calculating eta Earth ». Monthly Notices of the Royal Astronomical Society 487, n^o 1 (6 mai 2019) : 246–52. http://dx.doi.org/10.1093/mnras/stz1246.

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ABSTRACT Using the updated exoplanet population parameters of our previous study, which includes the planetary radius updates from Gaia DR2 and an inferred multiplicity distribution, we provide a revised η⊕ calculation. This is achieved by sampling planets from our derived population model and determining which planets meet our criterion for habitability. To ensure robust results, we provide probabilities calculated over a range of upper radius limits. Our most optimistic criterion for habitability provides an η⊕ value of $0.34\pm 0.02 \frac{\rm planets}{\rm star}$. We also consider the effects of multiplicity and the number of habitable planets each system may contain. Our calculation indicates that $6.4\pm 0.5{{\ \rm per\ cent}}$ of GK dwarfs have more than one planet within their habitable zone. This optimistic habitability criterion also suggests that $0.036\pm 0.009{{\ \rm per\ cent}}$ of solar-like stars will harbour five or more habitable planets. These tightly packed highly habitable systems should be extremely rare, but still possible. Even with our most pessimistic criterion, we still expect that $1.8\pm 0.2{{\ \rm per\ cent}}$ of solar-like stars harbour more than one habitable planet.

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Boro Saikia, Sudeshna, Theresa Lüftinger et Manuel Guedel. « Magnetic geometry and activity of cool stars ». Proceedings of the International Astronomical Union 14, S345 (août 2018) : 341–42. http://dx.doi.org/10.1017/s1743921319001935.

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AbstractStellar magnetic field manifestations such as stellar winds and EUV radiation are the key drivers of planetary atmospheric loss and escape. To understand how the central star influences habitability, it is very important to perform detailed investigation of the star’s magnetic field. We investigate the surface magnetic field geometry and chromospheric activity of 51 sun-like stars. The magnetic geometry is reconstructed using Zeeman Doppler imaging. Chromospheric activity is measured using the Ca II H& K lines. We confirm that the Sun’s large-scale geometry is dominantly poloidal, which is also true for slowly rotating stars. Contrary to the Sun, rapidly rotating stars can have a strong toroidal field and a weak poloidal field. This separation in field geometry appears at Ro=1. Our results show that detailed investigation of stellar magnetic field is important to understand its influence on planetary habitability.

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