The Problem of Life in the Universe and the Mode of Star Formation

Huang, Su-Shu

doi:10.1086/127417

Cited by 87 publications

(39 citation statements)

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“…Super-Earths in the habitable zone of their host stars, which by definition is the region where liquid water can be stable on the surface of a rocky planet (Huang 1959;Kasting et al 1993), currently garner considerable interest. For a detailed discussion of the HZ, we refer the reader to Selsis et al (2007) or Kaltenegger & Sasselov (2011) but summarize their most salient points.…”

Section: Gl 667ccmentioning

confidence: 99%

The HARPS search for southern extra-solar planets

Delfosse

Bonfils

Forveille

et al. 2013

A&A

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Context. M dwarfs have often been found to have super-Earth planets with short orbital periods. These stars are thus preferential targets in searches for rocky or ocean planets in the solar neighborhood. Aims. Our research group recently announced the discovery of one and two low-mass planets around the M1.5V stars Gl 433 and Gl 667C, respectively. We found these planets with the HARPS spectrograph on the ESO 3.6-m telescope at La Silla Observatory, from observations obtained during the guaranteed time observing program of that instrument. Methods. We obtained additional HARPS observations of those two stars, for a total of 67 and 179 radial velocity measurements for Gl 433 and Gl 667C, respectively, and present here an orbital analysis of these extended data sets and our main conclusions about both planetary systems. Results. One of the three planets, Gl 667Cc, has a mass of only M 2 sin i ∼ 4.25 M ⊕ and orbits in the central habitable zone of its host star. It receives only 10% less stellar energy from Gl 667C than the Earth receives from the Sun. However, planet evolution in the habitable zone can be very different if the host star is a M dwarf or a solar-like star, without necessarily questioning the presence of water. The two other planets, Gl 433b and Gl 667Cb, both have M 2 sin i of ∼5.5 M ⊕ and periods of ∼7 days. The radial velocity measurements of both stars contain longer timescale signals, which we fit with longer period Keplerians. For Gl 433, the signal probably originates in a magnetic cycle, while data of longer time span will be needed before conclusive results can be obtained for Gl 667C. The metallicity of Gl 433 is close to solar, while Gl 667C is metal poor with [Fe/H] ∼ −0.6. This reinforces the recent conclusion that the occurrence of super-Earth planets does not strongly correlate with the stellar metallicity.

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Section: Gl 667ccmentioning

confidence: 99%

The HARPS search for southern extra-solar planets

Delfosse

Bonfils

Forveille

et al. 2013

A&A

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“…A definição de Zona Habitável (ZH) foi introduzida em 1959 [68] como sendo a região ao redor de uma estrela em que o ciclo de fusão de H em He seja estável por alguns bilhões de anos, permitindo que um planeta possa manter água, no estado líquido, em sua superfície. A estrela fornece a energia e a água funciona como um solvente eficiente que participa ativamente das reações químicas.…”

Section: Zona Habitável E Habitabilidadeunclassified

Habitabilidade cósmica e a possibilidade de existência de vida em outros locais do universo

Vieira

Machaieie

Fornazier

et al. 2018

Rev. Bras. Ensino Fís.

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Este artigo aborda alguns aspectos relacionados ao conceito de vida como a conhecemos e explora a relação entre a evolução química do Universo e a produção dos elementos básicos da química prebiótica. Baseando-se no Modelo Cosmológico Padrão, são descritas as condições cosmológicas que levaram ao surgimento desses elementos e são mostradas evidências de que o Universo, em seus estágios primordiais, dispunha de elementos capazes de produzir substâncias orgânicas. É feita uma breve abordagem de como a química em ambientes astrofísicos leva à formação de compostos que fazem parte da cadeia de reações que conduz à formação dos "tijolos da vida". Finalmente, levantamos a hipótese que o universo poderia ter zonas habitáveis a partir dos primeiros 30 milhões da anos e que a condição de habitabilidade tem estreita relação com a sua evolução química, mesmo quando se leva em consideração a hipótese de diferentes universos. Palavras-chave: Habitabilidade Cósmica, Astrobiologia, Astroquímica.This article discusses some aspects related to the concept of life as we know it and explores the relationship between the chemical evolution of the Universe and the production of the basic elements of prebiotic chemistry. Based on the Standard Cosmological Model, the cosmological conditions that led to the appearance of these elements are described and evidences are shown that the Universe, in its primordial stages, had elements capable of producing organic substances. Next section gives a short overview on how chemistry in astrophysical environments leads to the formation of compounds that are part of the chain of reactions that leads to the formation of the "bricks of life." Finally, we mention that the universe could have habitable zones from the first 30 million years and that the habitability condition has a close relation with its chemical evolution, even when one takes into account the hypothesis of different universes. Keywords: Cosmic Habitability, Astrobiology, Astrochemistry. IntroduçãoA existência de vida no Universo tem permeado o pensamento humano desde os primórdios da civilização. Os avanços científicos do século XX, particularmente a partir da década de 1950, com a exploração do espaço exterior, permitiram um estudo mais aprofundado sobre uma série de fenômenos astronômicos que ampliaram, em muito, a compreensão do Universo. O cenário construído a partir dessas observações, em paralelo com avanços teóricos e modelos computacionais, indica que vivemos num Universo com cerca de 14 bilhões de anos, cuja composição inclui ∼ 96% de matéria e energia escuras, de origem ainda desconhecida, e ∼ 4% de matéria ordinária (basicamente constituída de prótons, nêutrons e elétrons) que deu origem às estrelas e galáxias, observadas principalmente através da emissão de radiação eletromagnética. Uma cronologia da evolução do modelo padrão, bem * Endereço para correspondência: fredsvieira@gmail.com como uma descrição atualizada e didática do "status"da cosmologia atual pode ser encontrada em [1][2][3][4][5][6][7].Esse cenário descreve o ...

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“…Planetary age as a necessary condition for life to emerge was first stressed by Huang (1959) and implicitly mentioned by Crick & Orgel (1973) in their concept of a Directed Panspermia.…”

Section: Initial Stages Of Habitabilitymentioning

confidence: 99%

Age aspects of habitability

Safonova

Murthy

Shchekinov³

2015

International Journal of Astrobiology

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A 'habitable zone' of a star is defined as a range of orbits within which a rocky planet can support liquid water on its surface. The most intriguing question driving the search for habitable planets is whether they host life. But is the age of the planet important for its habitability? If we define habitability as the ability of a planet to beget life, then probably it is not. After all, life on Earth has developed within only *800 Myr after its formation -the carbon isotope change detected in the oldest rocks indicates the existence of already active life at least 3.8 Gyr ago. If, however, we define habitability as our ability to detect life on the surface of exoplanets, then age becomes a crucial parameter. Only after life had evolved sufficiently complex to change its environment on a planetary scale, can we detect it remotely through its imprint on the atmosphere -the so-called biosignatures, out of which the photosynthetic oxygen is the most prominent indicator of developed (complex) life as we know it. Thus, photosynthesis is a powerful biogenic engine that is known to have changed our planet's global atmospheric properties. The importance of planetary age for the detectability of life as we know it follows from the fact that this primary process, photosynthesis, is endothermic with an activation energy higher than temperatures in habitable zones, and is sensitive to the particular thermal conditions of the planet. Therefore, the onset of photosynthesis on planets in habitable zones may take much longer time than the planetary age. The knowledge of the age of a planet is necessary for developing a strategy to search for exoplanets carrying complex (developed) life -many confirmed potentially habitable planets are too young (orbiting Population I stars) and may not have had enough time to develop and/or sustain detectable life. In the last decade, many planets orbiting old (9-13 Gyr) metal-poor Population II stars have been discovered. Such planets had had enough time to develop necessary chains of chemical reactions and may carry detectable life if located in a habitable zone. These old planets should be primary targets in search for the extraterrestrial life.

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The Problem of Life in the Universe and the Mode of Star Formation

Cited by 87 publications

References 0 publications

The HARPS search for southern extra-solar planets

The HARPS search for southern extra-solar planets

Habitabilidade cósmica e a possibilidade de existência de vida em outros locais do universo

Age aspects of habitability

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