Secular Acceleration of Io Derived from Mutual Satellite Events

Aksnes, K.; Franklin, F. A.

doi:10.1086/323708

Cited by 63 publications

(24 citation statements)

References 17 publications

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“…However, using the currently estimated tidal dissipation parameters to extrapolate backward in time predicts that the Moon was at Earth's surface about *2 Gyr ago (MacDonald, 1964), which contradicts the standard impact model for the lunar origin [note that numerous issues remain such as the origin of Earth's and the Moon's obliquities (Touma and Wisdom, 1994) and the perturbations from other planets (Ć uk, 2007)]. The deceleration of Io's orbital velocity has also been tentatively detected and seems broadly consistent with tidal theory (Aksnes and Franklin, 2001;Lainey et al, 2009). However, these data lie in the same regime, that of nearly circular orbits.…”

Section: Tidal Heatingmentioning

confidence: 97%

Tidal Venuses: Triggering a Climate Catastrophe via Tidal Heating

et al. 2013

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Traditionally, stellar radiation has been the only heat source considered capable of determining global climate on long timescales. Here, we show that terrestrial exoplanets orbiting low-mass stars may be tidally heated at highenough levels to induce a runaway greenhouse for a long-enough duration for all the hydrogen to escape. Without hydrogen, the planet no longer has water and cannot support life. We call these planets ''Tidal Venuses'' and the phenomenon a ''tidal greenhouse.'' Tidal effects also circularize the orbit, which decreases tidal heating. Hence, some planets may form with large eccentricity, with its accompanying large tidal heating, and lose their water, but eventually settle into nearly circular orbits (i.e., with negligible tidal heating) in the habitable zone (HZ). However, these planets are not habitable, as past tidal heating desiccated them, and hence should not be ranked highly for detailed follow-up observations aimed at detecting biosignatures. We simulated the evolution of hypothetical planetary systems in a quasi-continuous parameter distribution and found that we could constrain the history of the system by statistical arguments. Planets orbiting stars with masses < 0.3 M Sun may be in danger of desiccation via tidal heating. We have applied these concepts to Gl 667C c, a *4.5 M Earth planet orbiting a 0.3 M Sun star at 0.12 AU. We found that it probably did not lose its water via tidal heating, as orbital stability is unlikely for the high eccentricities required for the tidal greenhouse. As the inner edge of the HZ is defined by the onset of a runaway or moist greenhouse powered by radiation, our results represent a fundamental revision to the HZ for noncircular orbits. In the appendices we review (a) the moist and runaway greenhouses, (b) hydrogen escape, (c) stellar mass-radius and mass-luminosity relations, (d) terrestrial planet mass-radius relations, and (e) linear tidal theories.

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Section: Tidal Heatingmentioning

confidence: 97%

Tidal Venuses: Triggering a Climate Catastrophe via Tidal Heating

et al. 2013

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“…Although Ogilvie & Lin (2004) conclude that tidal dissipation rates of giant planets are not adequately represented by a constant Q-value, many parameterized tidal models rely on this quantity. Measurements of the heat flux from Jupiter's moon Io during the fly-by of the Voyager 1 spacecraft, combined with a specific model of the history of the orbital resonance, allowed for an estimate for the quality factor Q of Jupiter to be 2 × 10 5 < Q < 2 × 10 6 (Yoder 1979) while Aksnes & Franklin (2001) used historical changes in Io's orbit to infer that Q is around 10 5.3 . However, Greenberg et al (2008) pointed out that Q = ∞ is not ruled out (see also Peale & Greenberg 1980;Ioannou & Lindzen 1993).…”

Section: Tidal Modelsmentioning

confidence: 99%

Tidal effects on brown dwarfs: application to the eclipsing binary 2MASS J05352184-0546085

Heller¹,

Jackson²,

Barnes

et al. 2010

A&A

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Context. 2MASS J05352184−0546085 (2M0535−05) is the only known eclipsing brown dwarf (BD) binary, and so may serve as a benchmark for models of BD formation and evolution. However, theoretical predictions of the system's properties seem inconsistent with observations: i) the more massive (primary) component is observed to be cooler than the less massive (secondary) one; ii) the secondary is more luminous (by ≈10 24 W) than expected. Previous explanations for the temperature reversal have invoked reduced convective efficiency in the structure of the primary, connected to magnetic activity and to surface spots, but these explanations cannot account for the enhanced luminosity of the secondary. Previous studies also considered the possibility that the secondary is younger than the primary. Aims. We study the impact of tidal heating to the energy budget of both components to determine if it can account for the observed temperature reversal and the high luminosity of the secondary. We also compare various plausible tidal models to determine a range of predicted properties. Methods. We apply two versions of two different, well-known models for tidal interaction, respectively: i) the "constant-phase-lag" model; and ii) the "constant-time-lag" model and incorporate the predicted tidal heating into a model of BD structure. The four models differ in their assumptions about the rotational behavior of the bodies, the system's eccentricity and putative misalignments ψ between the bodies' equatorial planes and the orbital plane of the system. Results. The contribution of heat from tides in 2M0535−05 alone may only be large enough to account for the discrepancies between observation and theory in an unlikely region of the parameter space. The tidal quality factor Q BD of BDs would have to be 10 3.5 and the secondary needs a spin-orbit misalignment of 50 • . However, tidal synchronization time scales for 2M0535−05 restrict the tidal dissipation function to log(Q BD ) 4.5 and rule out intense tidal heating in 2M0535−05. We provide the first constraint on Q for BDs. Conclusions. Tidal heating alone is unlikely to be responsible for the surprising temperature reversal within 2M0535−05. But an evolutionary embedment of tidal effects and a coupled treatment with the structural evolution of the BDs is necessary to corroborate or refute this result. The heating could have slowed down the BDs' shrinking and cooling processes after the birth of the system ≈1 Myr ago, leading to a feedback between tidal inflation and tidal heating. Observations of old BD binaries and measurements of the Rossiter-McLaughlin effect for 2M0535−05 can provide further constraints on Q BD .

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“…It has been strongly debated which of these two opposing effects dominates, i.e., whether the time derivative dn 1 /dt of Io's mean motion is positive or negative. Lieske (1987), using mainly eclipse observations covering more than a hundred years, finds a small negative value, while Aksnes & Franklin (2001), based on analysis of a large number of mutual satellite events, find a bigger positive value, according to which Io is now spiraling slowly The two last-mentioned articles both conclude that Europa and Ganymede are now moving outward, so that the three inner satellites are moving away from the present Laplacian resonance.…”

Section: What Have We Learned From the Mutual Satellite Events?mentioning

confidence: 99%

Navigation, world mapping and astrometry with Galileo's moons

Aksnes

2010

Proc. IAU

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Abstract. Galileo realized that the four moons he discovered, besides supporting the heliocentric system, could also serve as a clock in the sky for longitude determination. Navigation at sea by this method did not prove practical but G. Cassini used it to improve land mapping. O. Rømer discovered that the interval between eclipses of the moons by Jupiter increased or decreased according to whether the Earth moved away from or toward Jupiter. He attributed this to the finite speed of light which he in 1676 determined with an error of about 25%. Timings of the eclipses by Jupiter have served to compute accurate orbits of the moons, notably by means of R. A. Sampson's theory of 1921. Beginning in 1973, light curves of mutual eclipses and occultations between pairs of moons have been made regularly at six years intervals. From these observations very accurate radii and positions of the moons have been obtained.

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Secular Acceleration of Io Derived from Mutual Satellite Events

Cited by 63 publications

References 17 publications

Tidal Venuses: Triggering a Climate Catastrophe via Tidal Heating

Tidal Venuses: Triggering a Climate Catastrophe via Tidal Heating

Tidal effects on brown dwarfs: application to the eclipsing binary 2MASS J05352184-0546085

Navigation, world mapping and astrometry with Galileo's moons

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