AN ANCIENT EXTRASOLAR SYSTEM WITH FIVE SUB-EARTH-SIZE PLANETS
By T. Campante, T. Barclay, Jonathan J. Swift, Daniel Huber, V. Adibekyan, W. Cochran, Christopher J. Burke, H. Isaacson, Elisa Quintana, G. Davies and 31 more. 2015
128 citations recorded by the source corpus.
The chemical composition of stars hosting small exoplanets (with radii less than four Earth radii) appears to be more diverse than that of gas-giant hosts, which tend to be metal-rich. This implies that small, including Earth-size, planets may have readily formed at earlier epochs in the universe's history when metals were more scarce. We report Kepler spacecraft observations of Kepler-444, a metal-poor Sun-like star from the old population of the Galactic thick disk and the host to a compact system of five transiting planets with sizes between those of Mercury and Venus. We validate this system as a true five-planet system orbiting the target star and provide a detailed characterization of its planetary and orbital parameters based on an analysis of the transit photometry. Kepler-444 is the densest star with detected solar-like oscillations. We use asteroseismology to directly measure a precise age of 11.2 ± 1.0 Gyr for the host star, indicating that Kepler-444 formed when the universe was less than 20% of its current age and making it the oldest known system of terrestrial-size planets. We thus show that Earth-size planets have formed throughout most of the universe's 13.8 billion year history, leaving open the possibility for the existence of ancient life in the Galaxy. The age of Kepler-444 not only suggests that thick-disk stars were among the hosts to the first Galactic planets, but may also help to pinpoint the beginning of the era of planet formation.
Subfields: Astronomy and Astrophysics, Instrumentation
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Citations in the corpus
- STELLAR AND PLANETARY PROPERTIES OF K2 CAMPAIGN 1 CANDIDATES AND VALIDATION OF 17 PLANETS, INCLUDING A PLANET RECEIVING EARTH-LIKE INSOLATION (2015, neutral): “Followup observations may be warranted to search for an additional planet in this system forming a resonant chain, similar to those observed around other stars (e.g., Swift et al. 2013; Campante et al. 2015).”
- Kepler Planet Masses and Eccentricities from TTV Analysis (2016, background): “Their extreme proximity to resonance likely plays a role in limiting the maximum combined eccentricity consistent with their TTVs. Kepler-526 b, 02 (Figure 9.35): Kepler-526 b and 02 are near a 5:4 MMR. Planet b does not induce any detectable TTV in Kepler-526.”
- Standing on the Shoulders of Dwarfs: the Kepler Asteroseismic LEGACY Sample. I. Oscillation Mode Parameters (2016, background): “…(Christensen-Dalsgaard et al. 2010; Basu et al. 2010; Howell et al. 2012; Metcalfe et al. 2012, 2014, 2015; Van Eylen et al. 2014; Lund et al. 2014c; Campante et al. 2015; Silva Aguirre et al. 2015), and frequency-difference ratios (Silva Aguirre et al. 2013, 2015; Lebreton & Goupil 2014).”
- THE IMPACT OF STELLAR MULTIPLICITY ON PLANETARY SYSTEMS. I. THE RUINOUS INFLUENCE OF CLOSE BINARY COMPANIONS (2016, methodology): “…13 M dwarfs for which we adopted new temperatures and metallicities based on medium resolution spectra obtained with the SNIFS spectrograph following the method given in Mann et al. (2013), and Kepler-444 for which we adopted the Hipparcos distance and input parameters by Campante et al. (2015).”
- How to Characterize Habitable Worlds and Signs of Life (2017, background): “The discovery of sub-Earth-sized planets around an 11-Gyr-old K-type MS star (Campante et al. 2015) illustrates that planets have formed early in the history of the Universe.”
- Ages and fundamental properties of Kepler exoplanet host stars from asteroseismology (2015, methodology): “…−0.058 4.18 +0.53 −0.35 92.37 +2.91 −2.85 Kepler-408 Marcy et al. (2014) 1925 9955598 5460± 75 0.08±0.10 0.890+0.009−0.011 0.883 +0.003 −0.006 1.821 +0.018 −0.018 4.495 +0.002 −0.002 0.598 +0.025 −0.023 6.98 +0.40 −0.50 66.80 +2.02 −2.05 Kepler-409 Marcy et al. (2014) 3158 6278762 5046± 74…”