An Estimate of the Age Distribution of Terrestrial Planets in the Universe: Quantifying Metallicity as a Selection Effect
By Charles H. Lineweaver. 2000
177 citations recorded by the source corpus.
Abstract Planets such as the Earth cannot form unless elements heavier than helium are available. These heavy elements, or “metals”, were not produced in the Big Bang. They result from fusion inside stars and have been gradually building up over the lifetime of the Universe. Recent observations indicate that the presence of giant extrasolar planets at small distances from their host stars is strongly correlated with high metallicity of the host stars. The presence of these close-orbiting giants is incompatible with the existence of Earth-like planets. Thus, there may be a Goldilocks selection effect: with too little metallicity, Earths are unable to form for lack of material; with too much metallicity, giant planets destroy Earths. Here I quantify these effects and obtain the probability, as a function of metallicity, for a stellar system to harbor an Earth-like planet. I combine this probability with current estimates of the star formation rate and of the gradual buildup of metals in the Universe to obtain an estimate of the age distribution of Earth-like planets in the Universe. The analysis done here indicates that three-quarters of the Earth-like planets in the Universe are older than the Earth and that their average age is 1.8±0.9 billion years older than the Earth. If life forms readily on Earth-like planets—as suggested by the rapid appearance of life on Earth—this analysis gives us an age distribution for life on such planets and a rare clue about how we compare to other life which may inhabit the Universe.
Subfields: Astronomy and Astrophysics
View Paper: https://www.semanticscholar.org/paper/282f2f76dac6d6d2651eee4187b8d30a49ddcc78
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In Astronomy and Astrophysics
Citations in the corpus
- The Galactic Habitable Zone: Galactic Chemical Evolution (2001, methodology): “As the metallicity dependencies of th phenomena are not yet well-constrained, we will not inclu them in the present study (for an attempt to treat these phen ena quantitatively, see Lineweaver (2001)).”
- Global Catastrophic Risks (2008, background): “One of the most interesting of many astrobiological results of recent years has been the study by Lineweaver (2001), showing that the Earth-like planets around other stars in the Galactic Habitable Zone (GHZ; Gonzalez et al., 2001) are, on average, 1.8 ± 0.9 Gyr older than our planet (see also the…”
- Spectroscopic [Fe/H] for 98 extra-solar planet-host stars. Exploring the probability of planet formation (2003, background): “…valid at least for the kind of planets that are now being discovered, has enormous implications for the theories of planetary formation and evolution (see Paper III for an extensive discussion on thissubject), as well as on studies of the frequency of planets in the galaxy (e.g. Lineweaver 2001).”