EVOLUTION OF THE SOLAR ACTIVITY OVER TIME AND EFFECTS ON PLANETARY ATMOSPHERES. II. {kappa}{sup 1} Ceti, AN ANALOG OF THE SUN WHEN LIFE AROSE ON EARTH

Journal Article · Sat May 01 00:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/714/1/384· OSTI ID:21448931

Ribas, I; Garces, A ^[1]; Porto de Mello, G F; Ferreira, L D ^[2]; Hebrard, E; Selsis, F ^[3]; Catalan, S ^[4]; Do Nascimento, J D

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1. Institut de Ciencies de l'Espai (CSIC-IEEC), Campus UAB, Facultat de Ciencies, Torre C5, parell, 2a pl., E-08193 Bellaterra (Spain)
2. Universidade Federal do Rio de Janeiro, Observatorio do Valongo, Ladeira do Pedro Antonio 43, CEP: 20080-090, Rio de Janeiro, RJ (Brazil)
3. Universite de Bordeaux, Observatoire Aquitain des Sciences de l'Univers, 2 rue de l'Observatoire, BP 89, F-33271 Floirac Cedex (France)
4. Centre for Astrophysics Research, Science and Technology Research Institute, University of Hertfordshire, Hatfield AL10 9AB (United Kingdom)

The early evolution of Earth's atmosphere and the origin of life took place at a time when physical conditions at the Earth were radically different from its present state. The radiative input from the Sun was much enhanced in the high-energy spectral domain, and in order to model early planetary atmospheres in detail, a knowledge of the solar radiative input is needed. We present an investigation of the atmospheric parameters, state of evolution, and high-energy fluxes of the nearby star {kappa}{sup 1} Cet, previously thought to have properties resembling those of the early Sun. Atmospheric parameters were derived from the excitation/ionization equilibrium of Fe I and Fe II, profile fitting of H{alpha}, and the spectral energy distribution. The UV irradiance was derived from Far-Ultraviolet Spectroscopic Explorer and Hubble Space Telescope data, and the absolute chromospheric flux from the H{alpha} line core. From careful spectral analysis and the comparison of different methods, we propose for {kappa}{sup 1} Cet the following atmospheric parameters: T{sub eff} = 5665 {+-} 30 K (H{alpha} profile and energy distribution), log g = 4.49 {+-} 0.05 dex (evolutionary and spectroscopic), and [Fe/H] = +0.10 {+-} 0.05 (Fe II lines). The UV radiative properties of {kappa}{sup 1} Cet indicate that its flux is some 35% lower than the current Sun's between 210 and 300 nm, it matches the Sun's at 170 nm, and increases to at least 2-7 times higher than the Sun's between 110 and 140 nm. The use of several indicators ascribes an age to {kappa}{sup 1} Cet in the interval {approx}0.4-0.8 Gyr and the analysis of the theoretical Hertzsprung-Russell diagram (H-R) suggests a mass {approx}1.04 M{sub sun}. This star is thus a very close analog of the Sun when life arose on Earth and Mars is thought to have lost its surface bodies of liquid water. Photochemical models indicate that the enhanced UV emission leads to a significant increase in photodissociation rates compared with those commonly assumed of the early Earth. Our results show that reliable calculations of the chemical composition of early planetary atmospheres need to account for the stronger solar photodissociating UV irradiation.

• OSTI ID: 21448931
• Journal Information: Astrophysical Journal, Vol. 714, Issue 1; Other Information: DOI: 10.1088/0004-637X/714/1/384; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABUNDANCE
CHEMICAL COMPOSITION
EARTH ATMOSPHERE
ENERGY SPECTRA
FAR ULTRAVIOLET RADIATION
HERTZSPRUNG-RUSSELL DIAGRAM
IONIZATION
MARS PLANET
PHOTOCHEMISTRY
PHOTOLYSIS
PLANETARY ATMOSPHERES
RADIANT FLUX DENSITY
SATELLITE ATMOSPHERES
SOLAR ACTIVITY
SOLAR SYSTEM EVOLUTION
SUN
TELESCOPES
ATMOSPHERES
CHEMICAL REACTIONS
CHEMISTRY
DECOMPOSITION
DIAGRAMS
ELECTROMAGNETIC RADIATION
EVOLUTION
FLUX DENSITY
INFORMATION
MAIN SEQUENCE STARS
PHOTOCHEMICAL REACTIONS
PLANETS
RADIATIONS
SPECTRA
STARS
STELLAR ACTIVITY
ULTRAVIOLET RADIATION