Thermal deformation of fuel elements

Safronov, E. Ya.; Briskman, B. A.; Bondarev, V. D.; Shishov, V. S.

doi:10.1007/bf01134255

Cited by 8 publications

(9 citation statements)

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“…It is possible that the ice giants shared a common formation path while giant impacts (GIs) occurring shortly after their formation have given them their distinct properties (Stevenson 1986;Podolak & Helled 2012). An oblique impact with a massive impactor could not only significantly alter Uranus' spin (Safronov 1966), but could also eject enough material to form a disk where its regular moons are formed. An oblique impact typically does not affect the planetary internal structure, so any composition barrier that inhibits convection is expected to remain.…”

Section: Introductionmentioning

confidence: 99%

Bifurcation in the history of Uranus and Neptune: the role of giant impacts

Reinhardt

Chau

Stadel

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Despite many similarities, there are significant observed differences between Uranus and Neptune: while Uranus is tilted and has a regular set of satellites, suggesting their accretion from a disk, Neptune's moons are irregular and are captured objects. In addition, Neptune seems to have an internal heat source, while Uranus is in equilibrium with solar insulation. Finally, structure models based on gravity data suggest that Uranus is more centrally condensed than Neptune. We perform a large suite of high resolution SPH simulations to investigate whether these differences can be explained by giant impacts. For Uranus, we find that an oblique impact can tilt its spin axis and eject enough material to create a disk where the regular satellites are formed. Some of the disks are massive and extended enough, and consist of enough rocky material to explain the formation of Uranus' regular satellites. For Neptune, we investigate whether a head-on collision could mix the interior, and lead to an adiabatic temperature profile, which may explain its larger flux and higher moment of inertia value. We find that massive and dense projectiles can penetrate towards the centre and deposit mass and energy in the deep interior, leading to a less centrally concentrated interior for Neptune. We conclude that the dichotomy between the ice giants can be explained by violent impacts after their formation.

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Section: Introductionmentioning

confidence: 99%

Bifurcation in the history of Uranus and Neptune: the role of giant impacts

Reinhardt

Chau

Stadel

et al. 2019

Monthly Notices of the Royal Astronomical Society

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show abstract

“…Another model suggested an expanding, tidal disk made of solids (Crida & Charnoz 2012). However, because the planet has an obliquity of 98 degrees, it was assumed that there has been an impact with an Earth-sized object (Safronov 1966;Harris & Ward 1982;Slattery et al 1992). This impact could have resulted a debris disk around the planet (similar to the case of Earth) where its moons formed (Dermott 1984;Stevenson 1984;Mousis 2004).…”

Section: Introductionmentioning

confidence: 99%

In Situ Formation of Icy Moons of Uranus and Neptune

Szulágyi

Cilibrasi

Mayer

2018

ApJL

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Satellites of giant planets thought to form in gaseous circumplanetary disks (CPDs) during the late planet-formation phase, but it was unknown so far whether smaller mass planets, such as the ice giants could form such disks, thus moons there. We combined radiative hydrodynamical simulations with satellite population synthesis to investigate the question in the case of Uranus and Neptune. For both ice giants we found that a gaseous CPD is created at the end of their formation. The population synthesis confirmed that Uranian-like, icy, prograde satellite-system could form in these CPDs within a couple of 10 5 years. This means that Neptune could have a Uranian-like moon-system originally that was wiped away by the capture of Triton. Furthermore, the current moons of Uranus can be reproduced by our model without the need for planet-planet impact to create a debris disk for the moons to grow. These results highlight that even ice giants -that among the most common masscategory of exoplanets -can also form satellites, opening a way to a potentially much larger population of exomoons than previously thought.

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“…Collisional tilting from roughly Earth-mass giant impacts is the most well-accepted theory for the tilt of Uranus and Neptune (Safronov 1966;Korycansky et al 1990;Slattery et al 1992;Morbidelli et al 2012;Kegerreis et al 2018). To explain Uranus's prograde equatorial satellite system, Morbidelli et al (2012) showed that the obliquity prior to the last tilting event must have been non-negligible, leading them to suggest that a multitude of such impacts were required.…”

Section: Application To Uranus and Neptunementioning

confidence: 99%

“…First, collisions with massive proto-planetary cores, such as the Moon-forming giant impact, can produce large ax-ial tilts. Similarly, giant impacts are routinely invoked in the origin scenarios of the extreme Uranian tilt (Safronov 1966;Morbidelli et al 2012). It is also possible that the obliquities of the giant planets were excited by an early process that twisted the total angular momentum vector of the Solar System, such as asymmetric infall during the system's initial collapse and formation (Tremaine 1991).…”

Section: Introductionmentioning

confidence: 99%

Excitation of Planetary Obliquities through Planet–Disk Interactions

Millholland

Batygin

2019

ApJ

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The tilt of a planet's spin axis off its orbital axis ("obliquity") is a basic physical characteristic that plays a central role in determining the planet's global circulation and energy redistribution. Moreover, recent studies have also highlighted the importance of obliquities in sculpting not only the physical features of exoplanets but also their orbital architectures. It is therefore of key importance to identify and characterize the dominant processes of excitation of non-zero axial tilts. Here we highlight a simple mechanism that operates early on and is likely fundamental for many extrasolar planets and perhaps even Solar System planets. While planets are still forming in the protoplanetary disk, the gravitational potential of the disk induces nodal recession of the orbits. The frequency of this recession decreases as the disk dissipates, and when it crosses the frequency of a planet's spin axis precession, large planetary obliquities may be excited through capture into a secular spin-orbit resonance. We study the conditions for encountering this resonance and calculate the resulting obliquity excitation over a wide range of parameter space. Planets with semi-major axes in the range 0.3 AU a 2 AU are the most readily affected, but large-a planets can also be impacted. We present a case study of Uranus and Neptune and show that this mechanism likely cannot help explain their high obliquities. While it could have played a role if finely tuned and envisioned to operate in isolation, large-scale obliquity excitation was likely inhibited by gravitational planet-planet perturbations.

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Thermal deformation of fuel elements

Cited by 8 publications

References 0 publications

Bifurcation in the history of Uranus and Neptune: the role of giant impacts

Bifurcation in the history of Uranus and Neptune: the role of giant impacts

In Situ Formation of Icy Moons of Uranus and Neptune

Excitation of Planetary Obliquities through Planet–Disk Interactions

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