Cornell: Odd Bodies, Rapid Spin Keep Cosmic Rings Close

[bystander]

Odd Bodies, Rapid Spin Keep Cosmic Rings Close
Cornell University | 2018 Nov 19

Forget those shepherding moons. Gravity and the odd shapes of asteroid Chariklo and dwarf planet Haumea – small objects deep in our solar system – can be credited for forming and maintaining their own rings, according new research in Nature Astronomy.

“Rings appear around Saturn, Jupiter, Neptune and Uranus, but scientists found rings around Chariklo and Haumea within the last few years. Chariklo and Haumea were the first small objects known to have rings, and we think that rings throughout the solar system are more common than we thought,” said Maryame El Moutamid ... “In the case of small bodies Chariklo and Haumea, gravity shepherds the rings. The rings are confined by the gravity because of the shape irregularity of their bodies.”

Until now, scientific literature generally assumed that the gravitational torques from shepherd moons around planets kept the rings in shape and prevented them from spreading and disappearing. Instead, this research shows that a topographic anomaly on the object, such as a mountain, may play a similar gravitational role as a “moon” to hold the rings together.

In addition to gravity, rapidly spinning cosmic bodies that create specific resonance also keep rings from expanding, dissipating and disappearing. ...

Ring Dynamics Around Non-Axisymmetric Bodies with Application to Chariklo and Haumea ~ B. Sicardy et al

• Nature Astronomy (online 19 Nov 2018) DOI: s41550-018-0616-8

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Ringed Chariklo © Don Davis

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<<The minor planet and centaur 10199 Chariklo, with a diameter of about 250 kilometres, is the smallest celestial object with confirmed rings and the fifth ringed celestial object ever discovered in the Solar System, after the gas giants and ice giants. Orbiting Chariklo is a bright ring system consisting of two narrow and dense bands, 6–7 km and 2–4 km wide, separated by a gap of 9 kilometres. The rings orbit at distances of about 400 kilometres from the centre of Chariklo, a thousandth the distance between Earth and the Moon. Chariklo's rings should disperse over a period of at most a few million years, so either they are very young, or they are actively contained by shepherd moons with a mass comparable to that of the rings. The team nicknamed the rings Oiapoque (the inner, more substantial ring) and Chuí (the outer ring), after the two rivers that form the northern and southern coastal borders of Brazil.>>

• My money is still on a [tidally locked] Brazil Nut shaped shepherding moon between Oiapoque and Chuí.