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

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

Overbye, Dennis. A Planetary System That Looks Familiar. New York Times. November 7, 2007. A team led by Debra Fischer of San Francisco State University, which included veteran researcher Geoff Marcy, reports for the first time the detection of a multi-planet solar system. Five worlds have so far been identified by wobbles induced in the star they orbit. Although by such inference not quite of earth size and location, more Venus-like, a life-temperate habitable zone around this sun can be specified. Marcy was interviewed this day by Jim Lehrer on The News Hour where he noted its historic significance which implies that conducive solar systems may abound across the celestial cosmos.

Overbye, Dennis. Cast Adrift in the Milky Way, Billions of Planets, All Alone. New York Times. May 19, 2011. A report on an announcement in Nature (473/349, 2011) by the Microlensing Observations in Astrophysics project, a New Zealand and Japan collaborative, together with the Optical Gravitational Lensing Experiment, based at the University of Warsaw, about new research that appears to reveal a celestial space filled with myriad adrift worlds. These lonely planets may have been ejected from the solar systems that gave them birth, or were only distantly related to a stellar origin. As a consequence, planets are now considered to outnumber stars. A commentary in the same Nature issue by Joachim Wambsganss of Heidelberg University avers: “The implications of this discovery are profound. We have a first glimpse of a new population of planetary-mass objects in our Galaxy.” Whatever might we earthlings make of a prolific, gravid cosmos that seems to seed itself with such ovular orbs?

Overbye, Dennis. From Kepler Data, Astronomers Find Galaxy Filled with More but Smaller Worlds. New York Times. February 27, 2014. A science report the latest findings of a plethora of earth-like planets by international teams who analyze Kepler satellite data. The news is based on several arXiv postings: Marcy, Geoffrey, et al. “Masses, Radii, and Orbits of Small Kepler Planets: The Transition from Gaseous to Rocky Planets” by Geoffrey Marcy, et al (arXiv:1401.4195); Jason Rowe, et al. “Validation of Kepler's Multiple Planet Candidates. III: Light Curve Analysis & Announcement of Hundreds of New Multi-planet Systems” by Jason Rowe, et al (arXiv:1402.6534); and “Validation of Kepler's Multiple Planet Candidates. II: Refined Statistical Framework and Descriptions of Systems of Special Interest” by Jack Lissauer, et al (arXiv:1402.6352).

The result is a deluge of small planets that has tipped the cosmic balance from the giant Jupiter-size worlds that were the earliest discovered to smaller, friendlier worlds. “Small planets from the size of Neptune to Earth make up the majority of the planets in the galaxy,” said Douglas Hudgins, exoplanet program scientist at NASA headquarters. (Overbye)

Conclusions about Planet Composition and Formation: In general, the distribution of planet masses for a given planet radius may be a function of orbital period and the type of host star, stemming from the complex processes of planet formation in a protoplanetary disk. The distribution of planet masses surely depends on planet radius, stellar mass, orbital semi-major axis and eccentricity, and on the chemical and thermodynamic properties of the protoplanetary region where they form. Thus, the measured planet masses and radii here inform only one plane of a multi-dimensional space that characterizes planet properties. (Marcy, et al, 28-29)

Overbye, Dennis. In the Hunt for Planets, Who Owns the Data? New York Times. June 15, 2010. The Kepler satellite search team is said to be holding back the release of findings lest they turn out to be premature and open to misinterpreted, which some have an issue with. But may we add after 15 years and some 500 planets, this epochal discovery of a universe which by its creative propensities is filled with earth-like bio-planets, similar to the 1930s realization of myriad galaxies, ought to be broadly admitted. And maybe inspire a better, wholesome appreciation of our precious home.

On Tuesday, astronomers operating NASA’s Kepler spacecraft will release a list of about 350 stars newly suspected of harboring planets, including five systems with multiple candidate planets. That data could dramatically swell the inventory of alien worlds, which now stands at 461, none of them habitable by the likes of us. Astronomers everywhere, who have been waiting since Kepler’s launch in March 2009 to get their hands on this data, will be rushing to telescopes to examine these stars in the hopes of advancing the grand quest of finding Earthlike planets capable of harboring life out there. (D 1)

Overbye, Dennis. Now in Sight: Far-Off Planets. New York Times. November 11, 2008. A news report on the order of magnitude advances in observational techniques, along with better data and pixel analysis, which are beginning to visually observe remote planetary objects.

Perryman, Michael. Resource Letter Exo-1: Exoplanets. American Journal of Physics. 82/6, 2014. The Princeton University astrophysicist and author of The Exoplanet Handbook provides an extensive overview and tutorial with many online and paper references.

Perryman, Michael. The Exoplanet Handbook. Cambridge: Cambridge University Press, 2018. The British astrophysicist based at the European Space Agency posts this 950 page second edition of his 2011 volume which is a most comprehensive technical reference to date. He is in the midst of active research, see Gaia Radial Velocity Spectrometer at arXiv:1804.09369.

Petigura, Erik, et al. A Plateau in the Planet Population below Twice the Size of Earth. Astrophysical Journal. 770/1, 2013. As the Abstract details, Petigura and Geoffrey Marcy, UC Berkeley, and Andrew Howard, University of Hawaii, have come upon in the latest analysis of the vast Kepler satellite data repository what seems to be a preferred zone of orbital earth analog dimensions.

We carry out an independent search of Kepler photometry for small transiting planets with sizes 0.5-8.0 times that of Earth and orbital periods between 5 and 50 days, with the goal of measuring the fraction of stars harboring such planets. We use a new transit search algorithm, TERRA, optimized to detect small planets around photometrically quiet stars. We restrict our stellar sample to include the 12,000 stars having the lowest photometric noise in the Kepler survey, thereby maximizing the detectability of Earth-size planets. We report 129 planet candidates having radii less than 6 RE found in three years of Kepler photometry (quarters 1-12). We gather Keck HIRES spectra for the majority of these targets leading to precise stellar radii and hence precise planet radii. We make a detailed measurement of the completeness of our planet search. We inject synthetic dimmings from mock transiting planets into the actual Kepler photometry. We then analyze that injected photometry with our TERRA pipeline to assess our detection completeness for planets of different sizes and orbital periods. We compute the occurrence of planets as a function of planet radius and period, correcting for the detection completeness as well as the geometric probability of transit, R /a. The resulting distribution of planet sizes exhibits a power law rise in occurrence from 5.7 RE down to 2 RE , as found in Howard et al. That rise clearly ends at 2 RE . The occurrence of planets is consistent with constant from 2 RE toward 1 RE . This unexpected plateau in planet occurrence at 2 RE suggests distinct planet formation processes for planets above and below 2 RE . (Abstract)

Petigura, Erik, et al. Prevalence of Earth-Size Planets Orbiting Sun-Like Stars. Proceedings of the National Academy of Sciences. Online November, 2013. Petigura and Geoffrey Marcy, UC Berkeley, and Andrew Howard, University of Hawaii, post an epochal report, worthy of front page news, about the spectacular findings of the Kepler satellite, along with worldwide computational and instrumental collaborations, which confirm that our encompassing universe, by intrinsic physical properties, is actually rife with as many planetary objects as stars. In regard, the preferred celestial system appears to be an incubator sun with habitable zones for orbital bioworlds. The New York Times article of November 5, 2013 is “Far-Off Planets Like the Earth Dot the Galaxy” by Dennis Overbye. Search each author above for more papers.

A major question is whether planets suitable for biochemistry are common or rare in the universe. Small rocky planets with liquid water enjoy key ingredients for biology. We used the National Aeronautics and Space Administration Kepler telescope to survey 42,000 Sun-like stars for periodic dimmings that occur when a planet crosses in front of its host star. We found 603 planets, 10 of which are Earth size and orbit in the habitable zone, where conditions permit surface liquid water. We measured the detectability of these planets by injecting synthetic planet-caused dimmings into Kepler brightness measurements. We find that 22% of Sun-like stars harbor Earth-size planets orbiting in their habitable zones. The nearest such planet may be within 12 light-years. (Petigura Significance)

The known odds of something — or someone — living far, far away from Earth improved beyond astronomers’ boldest dreams on Monday. Astronomers reported that there could be as many as 40 billion habitable Earth-size planets in the galaxy, based on a new analysis of data from NASA’s Kepler spacecraft. One out of every five sunlike stars in the galaxy has a planet the size of Earth circling it in the Goldilocks zone — not too hot, not too cold — where surface temperatures should be compatible with liquid water. (Overbye)

Pilat-Lohinger, Elke. The Role of Dynamics on the Habitability of an Earth-like Planet. International Journal of Astrobiology. 14/2, 2015. In an Exoplanet issue, a University of Vienna astrophysicist reaches a notable conclusion about our own solar system. It seems especially conducive because the orbital planets all lie in the same plane, and have basically circular orbits. Such a relative stability over a long time period is most favorable for a suitable biosphere upon which life can evolve and emerge to a noosphere able to observe itself and a planetary neighborhood.

Pudritz, Ralph, et al, eds. Planetary Systems and the Origins of Life. Cambridge: Cambridge University Press, 2007. Earth via humankind (earthkind) in retrospect learns how it (she/he) vicariously came to form and evolve from protoplanetary disks to animate, sentient vitality.

Quintana, Elisa, et al. An Earth-Sized Planet in the Habitable Zone of a Cool Star. Science. 344/277, 2014. A 23 member premier team from NASA, universities, and institutes in the US and France, including Jack Lissauer, find the best candidate so far (April) for a real Earth analog. An editorial Almost-Earth Tantalizes Astronomers with Promise of Worlds to Come cites “a wide new hunting found for extraterrestrial life.” And it is notable to see solar systems now commonly depicted with such habitable bands.

The quest for Earth-like planets is a major focus of current exoplanet research. Although planets that are Earth-sized and smaller have been detected, these planets reside in orbits that are too close to their host star to allow liquid water on their surfaces. We present the detection of Kepler-186f, a 1.11 ± 0.14 Earth-radius planet that is the outermost of five planets, all roughly Earth-sized, that transit a 0.47 ± 0.05 solar-radius star. The intensity and spectrum of the star’s radiation place Kepler-186f in the stellar habitable zone, implying that if Kepler-186f has an Earth-like atmosphere and water at its surface, then some of this water is likely to be in liquid form. (Abstract)

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