Hydrogen-helium demixing from first principles: From diamond anvil cells to planetary interiors

Morales, Miguel A.; Hamel, Sébastien; Caspersen, Kyle; Schwegler, Eric

doi:10.1103/physrevb.87.174105

Cited by 95 publications

(118 citation statements)

References 21 publications

Supporting

Mentioning

107

Contrasting

Order By: Relevance

“…The data also highlight the importance of localized rather than extended electronic changes in the warm dense noble gases, which may play an important role in chemical behavior. He electronic change has sometimes been expected to be not relevant to the miscibility question, on the argument that He remains insulating near demixing conditions (3,43); the data confirm this not to be the case. If He electronic changes controlled miscibility, then the insensitivity of He electronic properties to pressure (2,11,14,25,30) (Fig.…”

Section: Discussionmentioning

confidence: 85%

“…Significant theoretical and observational evidence for phase separation of helium and neon in the hydrogen-rich outer envelopes of giant planets has been reported (1-8), yet questions over the nature and even existence of this phase separation remain (2,42,43). This is in part due to limited direct experimental data on the hydrogen-helium-neon system at the conditions of phase separation: although hydrogen is observed in a metallic state at the interior conditions of giant planets (44), measurements on the electronic character of helium and neon at relevant densities and temperatures have been limited (12,13,17,45).…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Opacity and conductivity measurements in noble gases at conditions of planetary and stellar interiors

McWilliams

Dalton

Konôpková

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

The noble gases are elements of broad importance across science and technology and are primary constituents of planetary and stellar atmospheres, where they segregate into droplets or layers that affect the thermal, chemical, and structural evolution of their host body. We have measured the optical properties of noble gases at relevant high pressures and temperatures in the laserheated diamond anvil cell, observing insulator-to-conductor transformations in dense helium, neon, argon, and xenon at 4,000-15,000 K and pressures of 15-52 GPa. The thermal activation and frequency dependence of conduction reveal an optical character dominated by electrons of low mobility, as in an amorphous semiconductor or poor metal, rather than free electrons as is often assumed for such wide band gap insulators at high temperatures. White dwarf stars having helium outer atmospheres cool slower and may have different color than if atmospheric opacity were controlled by free electrons. Helium rain in Jupiter and Saturn becomes conducting at conditions well correlated with its increased solubility in metallic hydrogen, whereas a deep layer of insulating neon may inhibit core erosion in Saturn.rare gases | extreme conditions | warm dense matter | giant planet | white dwarf

show abstract

Section: Discussionmentioning

confidence: 85%

Section: Discussionmentioning

confidence: 99%

Opacity and conductivity measurements in noble gases at conditions of planetary and stellar interiors

McWilliams

Dalton

Konôpková

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

“…To explain helium depletion compared to the protosolar value (0.270 ± 0.005, Bahcall & Pinsonneault 1995), we assume that a helium phase transition occurs at a pressure P sep , between 0.8 and 4 Mbar according to the immiscibility calculations of Morales et al (2013). Helium settles down, increasing the abundance at the deeper layer, which in turn accounts for the depleted amount in the outer envelope.…”

Section: Modeling Jupitermentioning

confidence: 99%

Jupiter internal structure: the effect of different equations of state

Miguel

Guillot

Fayon

2016

A&A

105

161

View full text Add to dashboard Cite

Context. Heavy elements, even though they are a smaller constituent, are crucial to understand the formation history of Jupiter. Interior models are used to determine the amount of heavy elements in the interior of Jupiter, but this range is still subject to degeneracies because of the uncertainties in the equations of state. Aims. Before Juno mission data arrive, we present optimized calculations for Jupiter that explore the effect of different model parameters on the determination of the core and the mass of heavy elements of Jupiter. We compare recently published equations of state.Methods. The interior model of Jupiter was calculated from the equations of hydrostatic equilibrium, mass, and energy conservation, and energy transport. The mass of the core and heavy elements was adjusted to match the observed radius and gravitational moments of Jupiter. Results. We show that the determination of the interior structure of Jupiter is tied to the estimation of its gravitational moments and the accuracy of equations of state of hydrogen, helium, and heavy elements. Locating the region where helium rain occurs and defining its timescale is important to determine the distribution of heavy elements and helium in the interior of Jupiter. We show that the differences found when modeling the interior of Jupiter with recent EOS are more likely due to differences in the internal energy and entropy calculation. The consequent changes in the thermal profile lead to different estimates of the mass of the core and heavy elements, which explains differences in recently published interior models of Jupiter. Conclusions. Our results help clarify the reasons for the differences found in interior models of Jupiter and will help interpreting upcoming Juno data.

show abstract

“…The group of Morales et al (2013) instead performed direct thermodynamic integrations, thus including nonideal contributions to the entropy of mixing, but at the expense of subtantially more sparse sampling in helium number fraction x He . The results of the two groups are in reasonable agreement, diverging most noticeably at temperatures 3000 K, which on a present-day Jupiter (or Saturn) adiabat is well outside the transition from molecular to metallic hydrogen predicted by either group.…”

Section: Hydrogen-helium Phase Separationmentioning

confidence: 99%

“…Although the thermodynamic conditions for phase separation of helium from liquid metallic hydrogen have been evaluated since the early work of Stevenson (1975) and Straus et al (1977), quantitative knowledge covering the relevant pressures and H-He mixing ratios has only become available over the past several years as a result of ab initio simulations making use of density functional theory molecular dynamics (Morales et al 2009;Lorenzen et al 2009Lorenzen et al , 2011Morales et al 2013). The present work demonstrates that using ab initio results for the H-He phase diagram, a differentiating non-adiabatic Jupiter comprised of hydrogen and helium surrounding a dense core of heavy elements explain Jupiter's evolutionary state at the solar age.…”

mentioning

confidence: 99%

Bayesian Evolution Models for Jupiter With Helium Rain and Double-Diffusive Convection

Mankovich

Fortney

Moore

2016

ApJ

View full text Add to dashboard Cite

Hydrogen and helium demix when sufficiently cool, and this bears on the evolution of all giant planets at large separations at or below roughly a Jupiter mass. We model the thermal evolution of Jupiter, including its evolving helium distribution following results of ab initio simulations for helium immiscibility in metallic hydrogen. After 4 Gyr of homogeneous evolution, differentiation establishes a thin helium gradient below 1 Mbar that dynamically stabilizes the fluid to convection. The region undergoes overstable double-diffusive convection (ODDC), whose weak heat transport maintains a superadiabatic temperature gradient. With a generic parameterization for the ODDC efficiency, the models can reconcile Jupiter's intrinsix flux, atmospheric helium content, and radius at the age of the solar system if the Lorenzen et al. H-He phase diagram is translated to lower temperatures. We cast the evolutionary models in an MCMC framework to explore tens of thousands of evolutionary sequences, retrieving probability distributions for the total heavy element mass, the superadiabaticity of the temperature gradient due to ODDC, and the phase diagram perturbation. The adopted SCvH-I equation of state favors inefficient ODDC such that a thermal boundary layer is formed, allowing the molecular envelope to cool rapidly while the deeper interior actually heats up over time. If the overall cooling time is modulated with an additional free parameter to imitate the effect of a colder or warmer EOS, the models favor those that are colder than SCvH-I. In this case the superadiabaticity is modest and a warming or cooling deep interior are equally likely. Subject headings: planets and satellites: physical evolution -planets and satellites: interiors -planets and satellites: individual (Jupiter) -methods: statistical 1. INTRODUCTION Cool giant planets are relics of the protoplanetary systems from which they formed in the sense that they do not fuse protons, and they are well-bound enough that even hydrogen does not escape appreciably over tens of billions of years. Their thermal evolution is thus relatively simple, and understanding it empowers us to use the present states of giant planets to learn about their history and formation. The open questions about planet formation thus motivate a comprehensive theory of giant planet evolution, which will continue to be driven heavily by our own, well-studied giant planets, Jupiter and Saturn.A Henyey-type stellar evolution calculation for a Jupitermass object was first performed by Graboske et al. (1975), who showed that a convective, homogeneous sphere of fluid hydrogen and helium could cool to Jupiter's observed luminosity over roughly the right timescale, and noted that among all model inputs, the equation of state (EOS) and superadiabaticity of the temperature gradient have the strongest influence on the overall cooling time.These two fundamental physical inputs are closely related. The EOS (paired with a hydrostatic model) is necessary to translate the planet's tangible properties...

show abstract

Hydrogen-helium demixing from first principles: From diamond anvil cells to planetary interiors

Cited by 95 publications

References 21 publications

Opacity and conductivity measurements in noble gases at conditions of planetary and stellar interiors

Opacity and conductivity measurements in noble gases at conditions of planetary and stellar interiors

Jupiter internal structure: the effect of different equations of state

Bayesian Evolution Models for Jupiter With Helium Rain and Double-Diffusive Convection

Contact Info

Product

Resources

About