Tidal Evolution of Close-in Extrasolar Planets

By B. Jackson, Richard Greenberg, R. Barnes. Proceedings of the International Astronomical Union, 2007

322 citations recorded by the source corpus.

The distribution of eccentricities e of extrasolar planets with semimajor axes a > 0.2 AU is very uniform, and values for e are relatively large, averaging 0.3 and broadly distributed up to near 1. For a < 0.2 AU, eccentricities are much smaller (most e < 0.2), a characteristic widely attributed to damping by tides after the planets formed and the protoplanetary gas disk dissipated. Most previous estimates of the tidal damping considered the tides raised on the planets, but ignored the tides raised on the stars. Most also assumed specific values for the planets’ poorly constrained tidal dissipation parameter Qp. Perhaps most important, in many studies the strongly coupled evolution between e and a was ignored. We have now integrated the coupled tidal evolution equations for e and a over the estimated age of each planet, and confirmed that the distribution of initial e values of close-in planets matches that of the general population for reasonable Q values, with the best fits for stellar and planetary Q being ~105.5 and ~106.5, respectively. The accompanying evolution of a values shows most close-in planets had significantly larger a at the start of tidal migration. The earlier gas disk migration did not bring all planets to their current orbits. The current small values of a were only reached gradually due to tides over the lifetimes of the planets. These results may have important implications for planet formation models, atmospheric models of “hot Jupiters,” and the success of transit surveys.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/f56d0c957ecc435b663b2992c71a0eba2490608c

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Citations in the corpus

• WASP-19b: THE SHORTEST PERIOD TRANSITING EXOPLANET YET DISCOVERED (2010, background): “Values between 106 < Q′s < 10 9 are reasonable (Jackson et al. 2008, and references therein).”
• GEODYNAMICS AND RATE OF VOLCANISM ON MASSIVE EARTH-LIKE PLANETS (2008, background): “Our model does not consider tidal heating, which may be important for Earthlike planets on close eccentric orbits about low-mass stars (Jackson et al. 2008), nor does it take into account the energetics of the core (Nimmo 2007).”
• EXOPLANETARY SPIN–ORBIT ALIGNMENT: RESULTS FROM THE ENSEMBLE OF ROSSITER–MCLAUGHLIN OBSERVATIONS (2009, background): “Moreover, one would think that tidal damping of ψ by dissipation in the star should be fastest for systems with the most massive planets (see, e.g., Fabrycky et al. 2007; Jackson et al. 2008).”
• WASP-121 b: a hot Jupiter close to tidal disruption transiting an active F star (2015, background): “Despite being an essential parameter in the theory of stellar tides, Q′? is still poorly constrained, with estimates based on theoretical and observational studies ranging from to 105 to 109 (see e.g. Jackson et al. 2008, Ogilvie 2009, Penev et al. 2012).”
• Transiting exoplanets from the CoRoT space mission VIII. CoRoT-7b: the first Super-Earth with measured radius (2009, unknown): “Values from 105 to 105.5 (Lin et al. 1996; Jackson et al. 2008) would yield unrealistic small time scales of 70 Myr for the decay because it would be highly improbable to observe this planet today.”
• Photoevaporation and high-eccentricity migration created the sub-Jovian desert (2018, methodology): “The orbital decay rate is given by (e.g. Jackson et al. 2008): ȧ a =−9 2 ( G M∗ )1/2 R5∗Mp Q′∗ a−13/2, (8) where Q′? is the reduced tidal quality factor of the star.”
• FORETELLINGS OF RAGNARÖK: WORLD-ENGULFING ASYMPTOTIC GIANTS AND THE INHERITANCE OF WHITE DWARFS (2012, background): “Studies of Main-Sequence planet hosts suggestQ′⋆ in the range 105−1010 (e.g., Jackson et al. 2008; Penev & Sasselov 2011).”
• The Interior Structure, Composition, and Evolution of Giant Planets (2009, background): “Jackson et al. (2008a) have shown the orbits of hot Jupiters are still decaying due to the tide raised on the star by the planet, and that tidal heating in the not-to-distant past could have been appreciable (Jackson et al. 2008b).”
• ORBITAL PHASE VARIATIONS OF THE ECCENTRIC GIANT PLANET HAT-P-2b (2013, background): “…exoplanets have been shown to posses eccentricities in excess of that of Mercury (e = 0.2), which has made HATP-2b an interesting target for many theoretical studies concerning the evolution of the HAT-P-2 system (Jackson et al. 2008; Fabrycky 2008; Matsumura et al. 2008; Baraffe et al. 2008).”
• OBSERVATIONAL EVIDENCE FOR TIDAL DESTRUCTION OF EXOPLANETS (2009, methodology): “Note that Equations (1) and (2) include corrections to those presented by Jackson et al. (2008a).”
• On the tidal evolution of Hot Jupiters on inclined orbits (2009, background): “This estimate also appears consistent with the work of Jackson et al. (2008a), who found that one can reproduce the outer planet (a > 0.2 AU) eccentricity distribution from integrating the tidal evolution equations backwards in time for the observed close–in planets (a < 0.2 AU) quite well if Q ∼…”
• The GAPS Programme with HARPS-N at TNG - XIV. Investigating giant planet migration history via improved eccentricity and mass determination for 231 transiting planets (2017, unknown): “Tidal evolution models for the population of hot Jupiters as computed by Jackson et al. (2008, 2009) are also in general agreement with 10 6 < ∼ Q s < ∼ 10 7 , but our ignorance of the initial conditions of the close giant planet population ultimately hampers any possibility of precisely estimating…”
• TIDAL EVOLUTION OF CLOSE-IN PLANETS (2010, background): “It appears that at least some of these inflated planets could be explained as a result of past tidal heating (Jackson et al. 2008; Miller et al. 2009; Ibgui & Burrows 2009).”
• Tidal Heating of Extrasolar Planets (2008, methodology): “As a first cut at addressing this issue,we here present the tidal heating histories that would accompany the orbital evolution as computed in Jackson et al. (2008).”
• Tidal Dissipation in Stars and Giant Planets (2014, background): “…or constrain Q′ ∗ by statistical modelling of the observed orbital semi-major axes and eccentricities, either of populations or of single systems (Jackson et al. 2008, 2009; Hansen 2010; Schlaufman et al. 2010; Brown et al. 2011), there is as yet no convincing evidence of any orbital…”