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

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

Batygin, Konstantin, et al. The Origin of Universality in the Inner Edges of Planetary Systems. arXiv:2306.08822. KB, CalTech, Fred C. Adams and Juliette Becker, University of Michigan astrophysicists (search) describe some latest recognitions of independent celestial regularities as exhibited by any manner of solar orrery. See A Framework for the Architecture of Exoplanetary Systems at 2301.02374 and Order from Chaos by Lee Billings in Scientific American (May 2023) for concurrent notices. But will our special Earthumanity be able (in time) to realize the full implications without a phenomenal revolution?

he orbital period of the inner-most objects within the galactic census of planetary and satellite systems appears to be nearly universal. This paper presents a theoretical framework toward a simple explanation by way pfof the interplay between disk accretion, magnetic field generation by convective dynamos, and Kelvin-Helmholtz contraction. By this method we can express the magnetospheric truncation radius in astrophysical disks, to find that the relevant orbital frequency is independent of the mass of the host body. (Excerpt)

The principal goal of this letter is to explain this near-universality of the characteristic orbital period associated with magnetospheric disk truncation. Toward this end, we construct an analytic framework that draws upon conventional results from astrophysical dynamo theory, stellar structure, and disk accretion. Taken together, they reveal how planetary architectures are assembled within their natal nebulae, and shed light on the fundamental role played by magnetospheric cavities which shape the inner boundaries of the resulting planetary system. (2)

Behroozi, Peter and Molly Peeples. On the History and Future of Cosmic Planet Formation. arXiv:1508.01202. In a paper for the Monthly Notices of the Royal Astronomical Society, in this post-Kepler satellite era Space Telescope Science Institute astrophysicists describe a revolutionary universe with an inherent propensity to fill itself with galactic, stellar and planetary systems. By this vista, a collaborative, instrumental species on a conducive biosphere can begin to estimate how many other worldly civilizations might there be across its spatial expanse and temporal development. A natural philosophy reflection is in awe that one minute sapiensphere has such a capability to search, quantify and consider the whole sidereal cosmos from which it arose. Whatever fantastic scenario is being revealed, what great discovery are we invited to imagine of a genesis cosmos and of ourselves as co-creators?

We combine constraints on galaxy formation histories with planet formation models, yielding the Earth-like and giant planet formation histories of the Milky Way and the Universe as a whole. In the Hubble Volume (10^13 Mpc^3), we expect there to be ~10^20 Earth-like and ~10^20 giant planets; our own galaxy is expected to host ~10^9 and ~10^10 Earth-like and giant planets, respectively. Proposed metallicity thresholds for planet formation do not significantly affect these numbers. However, the metallicity dependence for giant planets results in later typical formation times and larger host galaxies than for Earth-like planets. The Solar System formed at the median age for existing giant planets in the Milky Way, and consistent with past estimates, formed after 80% of Earth-like planets. However, if existing gas within virialised dark matter haloes continues to collapse and form stars and planets, the Universe will form over 10 times more planets than currently exist. We show that this would imply at least a 92% chance that we are not the only civilisation the Universe will ever have, independent of arguments involving the Drake Equation. (Abstract)

Figure 2 Top-left panel: total Earth-like and giant planets formed in the Milky Way as a function of cosmic time. Giant planet counts have been shifted by a factor of 5 to allow better comparison with the Earth-like planet formation history. Top-right Panel: average planet density in the Universe as a function of cosmic time. Earth-like planet formation tracks the galaxy/cosmic star formation rates, whereas giant planet formation times are greater at late times due to their metallicity dependence. Blue squares mark the median formation times of each population. The vertical dotted line indicates the formation time of the Solar System, which occurred after 80% of present-day Earth-like planets and 50% of present-day giant planets were formed in the Milky Way. Bottom
Panels: planet formation rates and densities, respectively, for the Milky Way and the Universe as a whole. (3)

Bell, James. The Search for Habitable Worlds: Planetary Exploration in the 21st Century. Daedulus. 141/3, 2012. In this issue on Science in the 21st Century, the Arizona State University professor of earth and space sciences describes these awesome vistas that have suddenly opened. Among the array of achievements and promising paths is the realization, indeed an epochal revolution, of a galaxy and cosmos found to be filled with solar systems and earth-like worlds. Another incentive is new evidence of expanded habitats for living organisms from crustal depths and celestial reaches, over temperature and environmental extremes. However then, in a “Journal of the American Academy of Arts and Sciences,” could a common Earthwide project could be identified, recognized, and taken up by a personal planet just learning about its expectant cosmos?

The search for and detailed characterization of habitable environments on other worlds – places where liquid water, heat/energy sources, and biologically important organic molecules exist or could have once existed – is a major twenty-first-century goal for space exploration by NASA and other space agencies, motivated by intense public interest and highly ranked science objectives identified in recent National Academy decadal surveys. Through telescopic observations, terrestrial laboratory and field studies, and a “flyby, orbit, land, rove, and return” strategy for robotic exploration, particular emphasis will be placed on specific worlds already identified as potentially habitable: Mars, Jupiter's ocean moon Europa, and Saturn's icy and organic-bearing moons Titan and Enceladus. However, the potential abounds for surprising discoveries at many of our solar system's other planetary, satellite, and asteroidal destinations, as well as within newly discovered planetary systems around other stars. (Abstract, 8)

Planetary science is a relatively young, broadly interdisciplinary field that represents the merging of practices and practitioners from astronomy, physics, geology, geophysics, chemistry, geochemistry, atmospheric science, meteoritics, biology, mathematics, computer science, engineering, and other disciplines. (10) A prime and highly relevant example is the recent discovery in the terrestrial biology and paleontological communities of the phenomenal diversity of life on our own planet. (10) Thus, the newfound discovery of a much wider range of habitable environments on our own planet than had previously been thought has expanded the range of potentially habitable environments thought to exist (or to have existed) on other worlds. (11)

Benz, Willy, et al. Planet Population Synthesis. arXiv:1402.7086. A chapter to appear in Protostars and Planets VI (December 2014) by astronomers from Bern, Tokyo, Santa Cruz, CA, and Heidelberg. Our interest is to report growing perceptions, as this paper conveys, of a fertile universe filled with stochastic ovular worlds whereof those in conducive zones become habitable for life to evolve and emerge, as if some manner of cosmic selection.

With the increasing number of exoplanets discovered, statistical properties of the population as a whole become unique constraints on planet formation models provided a link between the description of the detailed processes playing a role in this formation and the observed population can be established. Planet population synthesis provides such a link. The approach allows to study how different physical models of individual processes (e.g., proto-planetary disc structure and evolution, planetesimal formation, gas accretion, migration, etc.) affect the overall properties of the population of emerging planets. The objective of this chapter is twofold: 1) provide an overview of the physics entering in the two main approaches to planet population synthesis and 2) present some of the results achieved as well as illustrate how it can be used to extract constraints on the models and to help interpret observations. (Abstract)

Beuther, Hennik, et al, eds. Protostars and Planets VI. Tucson: University of Arizona Press, 2014. A huge volume of 38 chapters by 250 authors from a July 2013 conference held in Heidelberg, Germany. Four parts are Molecular Clouds and Star Formation, Disk Formation and Evolution, Planetary Systems – Search, Formation, Evolution, and Astrophysical Conditions for Life. Into the 2010s by way of sophisticated satellite and telescopes, along with computational analysis, the sapient noosphere of a conducive biosphere proceeds to quantify its temporal and spatial cosmic neighborhood. With respect to prior V (2007) and IV (2000) editions, a radival difference is a new universe filled with myriad, vicarious worlds and solar systems of every conceivable kind. In this vista, a composite Earthkinder begins to reconstruct how galaxies and stars evolve, and planets form by accretions from gaseous planetesimal embryos. Multiple author papers range from The Origin and Universality of the Stellar Initial Mass Function to Astrophysical Conditions for Planetary Habitability, each with hundreds of references.

Apropos, on February 26, 2015 I heard Andrey Kravtsov, a University of Chicago astronomer, speak at the UM, Amherst on Order Out of Chaos: Formation of Galaxies in a Hierarchical Universe. Nowadays the dynamics of galactic evolution are displayed by streaming video images, along with mathematical explanations of any depth. Does the universe want to learn this so as to gain its own vision and self-comprehension? The speaker and audience are as much an intended phenomenon of this cosmic panorama as the dancing galaxies and sunny stars.

Borucki, William. KEPLER Mission: Development and Overview. Reports on Progress in Physics. 79/3, 2016. The NASA Ames Research Center astronomer and administrator relishes the grand success of this planet finder satellite endeavor which he proposed and championed for over thirty years. The discovery of a new kind of a procreative cosmos with an innate propensity to sow and seed itself with myriad orbital spheres in solar habitable incubators is an epochal revolution which remains to be realized and appreciated.

The Kepler Mission is a space observatory launched in 2009 by NASA to monitor 170 000 stars over a period of four years to determine the frequency of Earth-size and larger planets in and near the habitable zone of Sun-like stars, the size and orbital distributions of these planets, and the types of stars they orbit. Kepler is the tenth in the series of NASA Discovery Program missions that are competitively-selected, PI-directed, medium-cost missions. The Mission concept and various instrument prototypes were developed at the Ames Research Center over a period of 18 years starting in 1983. Beginning in 1992 at the start of the NASA Discovery Program, the Kepler Mission concept was proposed five times before its acceptance for mission development in 2001.

Analysis of the data to date has detected over 4600 planetary candidates which include several hundred Earth-size planetary candidates, over a thousand confirmed planets, and Earth-size planets in the habitable zone (HZ). These discoveries provide the information required for estimates of the frequency of planets in our galaxy. The Mission results show that most stars have planets, many of these planets are similar in size to the Earth, and that systems with several planets are common. Although planets in the HZ are common, many are substantially larger than Earth. (Abstract)

The objectives of the Kepler Mission are largely achieved. Because of the large number of exoplanets discovered and characterized, useful estimates of the parent distributions have been derived. The results show that most stars have planets, many of these planets are Earth-size, and a significant fraction are in the HZ of the host stars. These results bring to fore, the question raised by the Fermi Paradox: Where is everybody? Why haven’t the SETI searches been successful? Results from future instruments that can determine the chemical composition of the atmospheres of Earth-size planets in the HZ could provide an important clue to answer these fundamental questions. (45)

Borucki, William, et al. Kepler-62: A Five-Planet System with Planets of 1.4 and 1.6 Earth Radii in the Habitable Zone. Science. Online April 18, 2013. With dozens of coauthors including Geoffrey Marcy, Natalie Batalha, Lisa Kaltenegger, Jack Lissauer, Debra Fischer, and David Charbonneau, a news report about the most earth-like extrasolar analog candidate found so far. A front page article in the New York Times for April 19, 2013 “Two Promising Places to Live, 1,200 Light-Years from Earth” by Dennis Overbye cites this as a major Kepler satellite achievement to validate a galaxy and cosmos filled with neighboring, potentially conducive bioworlds. As noted by Overbye, an earlier technical paper is “Kepler-22b: A 2.4 Earth-Radius Planet in the Habitable Zone of A Sun-Like Star,” William Borucki with over fifty coauthors, in The Astrophysical Journal (745/2, 2012).

We present the detection of five planets—Kepler-62b, c, d, e, and f—of size 1.31, 0.54, 1.95, 1.61 and 1.41 Earth radii (R⊕), orbiting a K2V star at periods of 5.7, 12.4, 18.2, 122.4, and 267.3 days, respectively. The outermost planets (Kepler-62e and -62f) are super-Earth-size (1.25 < planet radius ≤ 2.0 R⊕) planets in the habitable zone (HZ) of their host star, receiving 1.2 ± 0.2 and 0.41 ± 0.05 times the solar flux at Earth’s orbit (S☉). Theoretical models of Kepler-62e and -62f for a stellar age of ~7 Gyr suggest that both planets could be solid, either with a rocky composition or composed of mostly solid water in their bulk. (Science Abstract)

Previous claims of Goldilocks planets with “just so” orbits snuggled up to red dwarf stars much dimmer and cooler than the Sun have had uncertainties in the size and mass and even the existence of these worlds, said David Charbonneau of the Harvard-Smithsonian Center for Astrophysics, an exoplanet hunter and member of the Kepler team. “This is the first planet that ticks both boxes,” Dr. Charbonneau said, speaking of the outermost planet, Kepler 62f. “It’s the right size and the right temperature.” Kepler 62f is 40 percent bigger than Earth and smack in the middle of the habitable zone, with a 267-day year. In an interview, Mr. Borucki called it the best planet Kepler has found. (NY Times)

Boss, Alan. The Crowded Universe: The Search for Living Planets. New York: Basic Books, 2009. The Carnegie Institution of Washington astronomer has been a pioneer advocate for the presence and detection of celestial worlds and solar systems. Due in February, we quote from the publisher’s website.

We are nearing a turning point in our quest for life in the universe-we now have the capacity to detect Earth-like planets around other stars. But will we find any? In The Crowded Universe, renowned astronomer Alan Boss argues that based on what we already know about planetary systems, in the coming years we will find abundant Earths, including many that are indisputably alive. Life is not only possible elsewhere in the universe, Boss argues - it is common.

Boss, Alan. Universal Life: An Inside Look Behind the Race to Discover Life Beyond Earth. New York: Oxford University Press, 2019. The Carnegie Institute for Science, Washington, DC astrophysicist and author is also chair of NASA’s Exoplanet Exploration Analysis Group. A veteran of individual and management contributions to national and worldwide exoplanet programs, this volume details the administrative machinations that went on so this endeavor to could find myriad exoworlds suggestive of a cosmic vitality. A special theme is the Kepler Space Telescope and what it took by its main advocate William Borucki to make it happen and succeed.

We now know that Earth-like planets are universal, and we expect that life will be just as universal, even if it is primarily microbial, as earth life was for most of its history. Considering the wide variety of exoplanets found to date, far beyond the imagination of the most fertile science fiction writers, we can only dream about the weird life forms that might inhabit these worlds and about how equally weird we would appear to them. (192)

Boyle, Rebecca. Astronomers Reimagine the Making of the Planets. Quanta. June 6, 2022. A science writer continues to survey our worldwise retrospective studies of how this Earth, our solar system, and orbital orrerys tend to array into myriad varieties. Her prior report was As Planet Discoveries Pile Up, a Gap Appears in the Pattern (May 16, 2019) which noted an absence in the galaxy of 1.5 to 2 times Earth size worlds. Three years and 5,000 total findings later, still “none that remotely resemble ours” was found She comments that Alessandro Morbidelli, a leading researcher, finds the situation quite curious. A prime reference is then Planet Formation Theory in the Era of ALMA and Kepler: From Pebbles to Exoplanets by Joanna Drazkowaka and nine coauthors including AM at arXiv:2203.09759 (see herein).

Burkhardt, Christoph. Planetary Genealogy. arXiv:2203.02203. A University of Munster researcher deftly employs this familial metaphor so to impart a deep sense of an astro-ancestry.

The detection of exoplanets and accretion disks around newborn stars has spawned novel models of how our Solar System formed and evolved. In regard, stable isotope anomalies in meteorites are now used as key tracers of material flow in the early Solar System which allows cosmochemists to establish a "planetary isotopic genealogy". This concept has advanced our understanding of Solar System evolution from the collapse of the Sun's parental molecular cloud. (Abstract excerpt)

Isotope anomalies are adding new vistas to the Solar System’s dynamical evolution from the molecular cloud to the formation of the terrestrial planets. As if genetic tracers, they reveal a bimodality among planetary bodies that dates back to the early infall stage. Many questions remain, but, planetary isotope genetics has the potential to bring meteoritics, astronomical observations, and modeling together towards a unified model for early Solar System evolution. (8)

Burn, Remo,et al. A radius valley between migrated steam worlds and evaporated rocky cores. Nature Astronomy. 8/4, 2024. MPI Astronomy, University of Bern, IBM Research, and Geneva Observatory and Ludwig-Maximilians-University astrophysicists including Julia Venturini are able to detect the presence of an integral solar system topology which serves to array and constrain planetary movements. See also Peas-in-a-Pod Across the Radius Valley: Rocky Systems are Less Uniform in Mass but More Uniform in Size and Spacing by Armaan Goyal and Songhu Wang at arXiv:2405.14091 and Wide Binary Orbits are Preferentially Aligned with the Orbits of Small Planets, but Probably Not Hot Jupiters by Sam Christian, et al at 2405.10379.

The radius valley (or gap) which separates smaller super-Earths from larger sub-Neptunes, is a key feature that theoretical models must explain. Here we use an advanced coupled formation and evolution model that describes the planets’ growth and evolution starting from solid, moon-sized bodies in the protoplanetary disk to mature Gyr-old planetary systems. The model results demonstrate that the observed radius valley can be interpreted as the separation of less massive, rocky super-Earths formed in situ from more massive, ex situ, water-rich sub-Neptunes. Therefore, we provide a hybrid theoretical explanation of the radius gap and cliff caused by both planet formation (orbital migration) as well as evolution (atmospheric escape). (Excerpt)

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