III. Ecosmos: A Revolutionary Fertile, Habitable, Solar-Bioplanet, Incubator Lifescape

H. Stellar Planetary Systems: A Diverse Profusion of Galaxies, Solar Orrerys and Habitable Zones

Adibekyan, Vardan. Formation and Evolution of Exoplanets in Different Environments. arXiv:1701.01661. We cite this contribution by the University of Porto, Portugal astronomer as a example of how a worldwise Earthkinder is proceeding to study and learn about galactic condensations of a prolific cosmos as it engenders an infinity of orbital worlds. See also Observational Evidence for Two Distinct Giant Planet Populations (1705.06090), and Big, Bigger, Biggest in The Economist for July 15.

The ultimate goal of exoplanetologists is to discover life outside our Earth and to fully understand our place in the Universe. Even though we have never been closer to attaining this goal, we still need to understand how and where the planets (efficiently) form. In this manuscript I briefly discuss the important role of stellar metallicity and chemistry on the formation and evolution of exoplanets.

Adibekyan, Vardan, et al. How Alien can Alien Worlds Be?. arXiv:1710.07482. As exoplanetary studies shift from an initial detection stage to an extensive telescopic, instrumental, and computational phase, Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, Portugal researchers provide another review of how this latest project might proceed with regard to what kind of exoworld geochemistry, metallicity, atmospheres, conductivity for life, and more.

In an attempt to select stars that can host planets with characteristics similar to our own, we selected seven solar-type stars known to host planets in the habitable zone and for which spectroscopic stellar parameters are available. For these stars we estimated 'empirical' abundances of O, C, Mg and Si, which in turn we used to derive the iron and water mass fraction of the planet building blocks. Our results show that if rocky planets orbit these stars they might have significantly different compositions between themselves and different from that of our Earth. However, for a meaningful comparison between the compositional properties of exoplanets in the habitable zone and our own planet, a far more sophisticated analysis of a large number of systems with precise mass and radius of planets, and accurate chemical abundances of the host stars. The work presented here is merely the first humble step in this direction. (Abstract)

During (at least) the 11.2 billion year-long history of exoplanet formation in the Milky Way, the interstellar gas has chemically evolved significantly. Some recent works detail how abundances of different chemical elements changes with time and place in the Galaxy. Abundances of these different individual heavy elements and specific elemental ratios (e.g. Mg/Si and Fe/Si) are, in turn, very important for the formation, orbital architecture, structure and composition and even maybe for ’habitability’ of the exoplanets. This discussion leads to a conclusion that the chemical environment i.e., time and place in the Milky Way, play a crucial role for the formation of planets and their main characteristics. (1)

Adibekyan, Vardan, et al. Which Type of Planets do We Expect to Observe in the Habitable Zone? Origins of Life and Evolution of Biospheres. Online June, 2016. With Pedro Figueira and Nuno Santos, University of Porto, Portugal, astrophysicists proceed to quantify our myriad new neighbors so as to identify and characterize what manner are likely to be in conducive locales as our home Earth. See also by the lead author Formation and Evolution of Exoplanets in Different Environments at arXiv:1701.01661. And how fantastic is it that a collaborative planetary species can begin a cosmic census across a widest stochastic diversity of potentially ovular worlds.

We used a sample of super-Earth-like planets detected by the Doppler spectroscopy and transit techniques to explore the dependence of orbital parameters of the planets on the metallicity of their host stars. We confirm the previous results (although still based on small samples of planets) that super-Earths orbiting around metal-rich stars are not observed to be as distant from their host stars as we observe their metal-poor counterparts to be. The orbits of these super-Earths with metal-rich hosts usually do not reach into the Habitable Zone (HZ), keeping them very hot and inhabitable. We found that most of the known planets in the HZ are orbiting their GK-type hosts which are metal-poor. The metal-poor nature of planets in the HZ suggests a high Mg abundance relative to Si and high Si abundance relative to Fe. These results lead us to speculate that HZ planets might be more frequent in the ancient Galaxy and had compositions different from that of our Earth. (Abstract)

The discussion presented above, on the dependence of composition of planets on the chemical properties of their hosts, leads us to speculate that probably the frequency of planets in the HZ was higher in the ancient Galaxy and in the outer disk of the Galaxy, when/where the metallicity is on average lower than in the solar neighborhood. Moreover, most of these planets in the HZ (because of lower metallicity, high Si/Fe, and high Mg/Si) should have composition that might be very different than that of our Earth. (7)

Airapetian, Vladimir, et al. Impact of Space Weather on Climate and Habitability of Terrestrial-type Exoplanets. International Journal of Astrobiology. Online August, 2019. A forty-five member collaboration from NASA, across the USA, Austria, Germany, Japan, and Ireland provide an extended review and preview of this “astro-spheric” phase of a biocosmic spacescape which fills itself with evolutionary life bearing planets in solar incubators. A 206 page edition is accessible at arXiv:1905.05093.

Andrews, Sean, et al. The Disk Substructures at High Angular Resolution Project (DSHARP): 1. Motivation, Sample, Calibration, and Overview. Astrophysical Journal Letters. 869/2, 2018. An introduction to Focus on DSHARP Results, a 10 paper collection herein about the project and its first round of findings. Their significance is noted in Science as Hints of Young Planets Puzzle Theorists by Daniel Clery (362/1337, 2018), see second quote.

We introduce the Disk Substructures at High Angular Resolution Project (DSHARP), one of the initial Large Programs conducted with the Atacama Large Millimeter/submillimeter Array (ALMA). The primary goal is to find and characterize substructures in the spatial distributions of solid particles for a sample of 20 nearby protoplanetary disks, using very high resolution observations of their 240 GHz continuum emission. These data provide a first look at the small-scale disks that are relevant to planet formation, their prevalence, morphologies, spatial scales, spacings, symmetry, and amplitudes, with a variety of disk and stellar hosts. Here we discuss the motivation for the project, describe the survey design and the sample properties, detail the observations and data calibration, highlight some basic results, and provide a general overview of the key conclusions that are presented in more detail in a series of accompanying articles. (Abstract excerpt)

HL Tau, a mere stripling of a star at no more than 1 million years old, was swaddled in a surprise. Four years ago, the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile revealed rings and gaps in a bright disk of dust around HL Tau—apparently swept clean by unseen planets that had formed millions of years earlier than astronomers thought possible. But now, an ALMA survey of 20 disks around nearby young stars suggests the precocious planets around HL Tau are no anomalies. The results, published in 10 papers last week in The Astrophysical Journal Letters, suggest disks with rings, gaps, and other features are the norm, not an exception—a result that will keep theorists busy for years. (Clery Summary)

Arbesman, Samuel and Gregory Laughlin. A Scientometric Prediction of the Discovery of the First Potentially Habitable Planet with a Mass Similar to Earth. PLoS One. 5/10, 2010. Since detection of an earth-like extrasolar planet appears imminent, Harvard University and University of California, Santa Cruz, scientists propose a “novel metric of habitability” to facilitate its actual perception and veracity. By such lights, the epochal event is expected to occur in mid 2011.

Armstrong, David, et al. Transit Shapes and Self-Organizing Maps as a Tool for Ranking Planetary Candidates. arXiv:1611.01968. Astrophysicists Armstrong and Don Pallacco, University of Warwick, and Alex Santerne, University of Marseille, apply these neural methods to help analyze the vast amounts of data as the Kepler satellite finds ever more astral objects.

Arthur, Rudy, et al.. . Life on the Edge: Using Planetary Context to Enhance Biosignatures and Avoid False Positives.. arXiv:2504.18431.. University of Exeter astroscholars including Arwin Nicholson (search RA) draw on their extensive Gaia-like Earth system studies to propose careful, specific ways of detecting and evaluating exoplanet bioatmospheres. See also Prospects for Detecting Signs of Life on Exoplanets in the JWST Era by Sara Seager et al at arXiv:2504.12946 and Comparative Biosignatures by Teraza, Constantinou, et al at arXiv:2505.01512 for more considerations.

We use a probability theory framework to discuss the search for biosignatures which allows us to analyse biosignatures to provide convincing evidence of extraterrestrial life. Our perspective of functional planetary views opens to a “peribiosignatures” concept, based on past Gaia studies, where life is unlikely. Finally, we discuss the implications of context dependence on observational strategy, suggesting that searching the edges of the habitable zone rather than the middle might be more likely to provide convincing evidence of life. (Abstract)

Aschwanden, Markus and Felix Scholkmann. Exoplanet Predictions Based on Harmonic Orbit. arXiv:1705.07138. In a 21st century scientific paper that would please Johannes Kepler some four hundred years on, astrophysicists can now discern and quantify that orbital planets do in fact display an intrinsic orderly motion. See also Self-Organizing Systems in Planetary Systems by Aschwanden at 1705.07138 and Order out of Randomness by MA, et al at 1708.03394.

The current exoplanet database includes 5454 confirmed planets and candidate planets observed with the KEPLER mission. We find 932 planet pairs from which we extract distance and orbital period ratios. While earlier studies used the Titius-Bode law or a generalized version with logarithmic spacing, which both lack a physical model, we employ here the theory of harmonic orbit resonances, which contains quantized ratios instead, to explain the observed planet distance ratios and to predict undetected exoplanets. Our orbital predictions includes 171 exoplanets, 2 Jupiter moons, one Saturn moon, 3 Uranus moons, and 4 Neptune moons. (Abstract excerpt)

The existence of quantized values in planetary distances represents a system with (non-random) order, which falls into the category of self-organizing systems. Self-organizing systems are characterized by regular geometric patterns that result from frequent local interactions in an initially disordered system (e.g., the libration of coupled pendulums). The principle of self-organization, however, should not be confused with the concept of self-organized criticality in nonlinear dissipative systems, which is common in astrophysics also. (6)

Azua-Bustos, Armando and Cristian Vega-Martinez. The Potential for Detecting ‘Life as We Don’t Know It’ by Fractal Complexity Analysis. International Journal of Astrobiology. Online June, 2013. Pontificia Universidad Católica de Chile, and Instituto de Astrofísica de La Plata, Argentina scientists suggest a clever approach whereof the deep proclivity of living systems to form self-similar, iterative geometries could provide a viable indicator for searches of their presence across the cosmos.

Finding life in the Universe entirely different to the one evolved on Earth is probable. This is a significant constraint for life-detecting instruments that were sent and may be sent elsewhere in the solar system, as how could we detect life as ‘we don't know it’? How could we detect something when we have no prior knowledge of its composition or how it looks like? Here we argue that disregarding the type of lifeform that could be envisioned, all must share in common the attribute of being entities that decrease their internal entropy at the expense of free energy obtained from its surroundings. As entropy quantifies the degree of disorder in a system, any envisioned lifeform must have a higher degree of order than its supporting environment. Here, we show that by using fractal mathematics analysis alone, one can readily quantify the degree of entropy difference (and thus, their structural complexity) of living processes (lichen growths and plant growing patterns in this case) as distinct entities separate from its similar abiotic surroundings. This approach may allow possible detection of unknown forms of life based on nothing more than entropy differentials of complementary datasets. (Abstract)

Balbi, Amedeo and Manasvi Lingam. Beyond Mediocrity: How Common is Life?.. arXiv:2305.05395. University of Rome and Florida Institute of Technology exoscientists (search each) gather wide and deep considerations about to better evaluate the celestial presence of living systems. Yes, there may be many habitable worlds, but our thought process need go beyond this to engage a stochastic array of conditions, stellar varieties, and more contingencies. See also A Bayesian Analysis of Technological Intelligence in Land and Oceans by Manasvi Lingam, et al at arXiv:2305.05989.

The probability that life spontaneously emerges in a suitable environment (abiogenesis) is a major issue in astrobiology, which begs an accepted theory for the origin of life. In this paper, we adopt a Bayesian statistical approach to rigorously infer the lower evident-based bounds for abiogenesis. We note that the possible existence of many habitable worlds does not imply that life should be common in the universe. If habitable worlds are uncommon, for an agnostic prior, a deterministic scenario for the origin of life might be favoured over one where abiogenesis is a fluke event. (Excerpt)

Baraffe, I., et al. The Physical Properties of Extra-Solar Planets. Reports on Progress in Physics. 73/016901, 2010. An historic revision and expansion is going on about what kind of celestial cosmos that human beings find ourselves in, which has not yet run its course nor is widely appreciated. Rather than earthly biospheres as anomalous rarities, a default just a decade ago, planetary objects of any and all kind seem to abound wherever they can. This advance and vista has lately matured to the extent that astronomers can write this tutorial paper about their observation, formation, interior structure, atmospheres, evolution, star-planet interaction, and so on.

Previous   1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10  Next  [More Pages]