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TOPIC: Uranus
Blobrana


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Uranus
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Two outer rings of Uranus were found in 2003-2005 in Hubble Space Telescope photos.

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Blobrana


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On this day in 1781 William Herschel discovered Uranus.

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The rings of Uranus
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The rings of Uranus were discovered on March 10, 1977, by James L. Elliot, Edward W. Dunham, and Douglas J. Mink

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RE: Uranus
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Title: Chemical processes in the deep interior of Uranus
Authors: Ricky Chau, Sebastien Hamel, William J. Nellis

The unusual magnetic fields of the planets Uranus and Neptune represent important observables for constraining and developing deep interior models. Models suggests that the unusual non-dipolar and non-axial magnetic fields of these planets originate from a thin convective and conducting shell of material around a stably stratified fluid core. Here, we present an experimental and computational study of the physical properties of a fluid representative of the interior of Uranus and Neptune. Our electrical conductivity results confirm that the core cannot be well mixed if it is to generate non-axisymmetric magnetic fields. The molecular dynamics simulations highlight the importance of chemistry on the properties of this complex mixture, including the formation of large clusters of carbon and nitrogen and a possible mechanism for a compositional gradient, which may lead to a stably stratified core.

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Uranus moons Cordelia and Ophelia
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Today is the 25th Anniversary (1986) of  Rich Terrile's discovery of the Uranus moons Cordelia and Ophelia.
Cordelia is the innermost moon of Uranus. It was discovered from the images taken by Voyager 2 on January 20, 1986, and was given the temporary designation S/1986 U 7.
Ophelia was also discovered from the images taken by Voyager 2 on January 20, 1986, and was given the temporary designation S/1986 U 8.

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Blobrana


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RE: Uranus
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Discovery of Uranus Moon Cressida. (1986)

25th Anniversary (1986), Stephen Synnott's Discovery of Uranus Moon Cressida.

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Uranus in the constellation Pisces, 0.00 UT, 1st August, 2010.

Magnitude= 5.8mag  
Best seen from 23.2h - 3.5h
RA= 0h01m50s  Dec= -0°38.7' (J2000)
Distance=19.448AU
Elongation=128° 
Diameter=3.6"

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Blobrana


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On this day in 1781 William Herschel discovered Uranus.

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Blobrana


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Un scénario sans collision pour le basculement d'Uranus

Uranus est une planète très particulière du Système solaire : son axe de rotation sur elle-même est presque dans le plan de son orbite autour du Soleil, au lieu d'en être quasi perpendiculaire, comme pour les autres planètes. Deux astronomes de l'Institut de Mécanique Céleste et de Calcul des Ephémérides (IMCCE : INSU-CNRS, Observatoire de Paris) proposent un mécanisme de résonance avec un satellite, aujourd'hui disparu, qui aurait fait basculer l'axe de rotation d'Uranus, lors de la formation du Système solaire.
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Title: A collisionless scenario for Uranus tilting
Authors: Gwenaël Boué, Jacques Laskar
(Version v2)

The origin of the high inclination of Uranus' spin-axis (Uranus' obliquity) is one of the great unanswered questions about the Solar system. Giant planets are believed to form with nearly zero obliquity, and it has been shown that the present behaviour of Uranus' spin is essentially stable. Several attempts were made in order to solve this problem. Here we report numerical simulations showing that Uranus' axis can be tilted during the planetary migration, without the need of a giant impact, provided that the planet had an additional satellite and a temporary large inclination. This might have happened during the giant planet instability phase described in the Nice model. In our scenario, the satellite is ejected after the tilt by a close encounter at the end of the migration. This model can both explain Uranus' large obliquity and bring new constraints on the planet orbital evolution.

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Title: A collisionless scenario for Uranus tilting
Authors: Gwenaël Boué, Jacques Laskar

The origin of the high inclination of Uranus' spin-axis (Uranus' obliquity) is one of the great unanswered questions about the Solar system. Giant planets are believed to form with nearly zero obliquity, and it has been shown that the present behaviour of Uranus' spin is essentially stable. Several attempts were made in order to solve this problem. Here we report numerical simulations showing that Uranus' axis can be tilted during the planetary migration, without the need of a giant impact, provided that the planet had an additional satellite and a temporary large inclination. This might have happened during the giant planet instability phase described in the Nice model. In our scenario, the satellite is ejected after the tilt by a close encounter at the end of the migration. This model can both explain Uranus' large obliquity and bring new constraints on the planet orbital evolution.

Read more (511kb, PDF)

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