NASA: Saturn - Possible New Moon Forming

[MargaritaMc]

Possible New Moon Forming Around Saturn
April 14, 2014: NASA's Cassini spacecraft has documented the formation of a small icy object within the rings of Saturn. Informally named "Peggy," the object may be a new moon. Details of the observations were published online today by the journal Icarus.
"We have not seen anything like this before," said Carl Murray of Queen Mary University of London, and the report's lead author. "We may be looking at the act of birth, where this object is just leaving the rings and heading off to be a moon in its own right."

Click to view full size image

Read more at
http://science.nasa.gov/science-news/sc ... r_newmoon/

There isn't a link from this news release to the article in Icarus and I've not yet been able to find it at the journal's website.

Margarita

[bystander]

Cassini Images May Reveal Birth Of A New Saturn Moon
http://www.jpl.nasa.gov/news/news.php?release=2014-112
http://www.ciclops.org/view/7879

Commotion at Ring's Edge May Be Effect of Small Icy Object
http://photojournal.jpl.nasa.gov/catalog/PIA18078
http://www.ciclops.org/view/7878

[neufer]

[Peggy] is not expected to grow any larger, and may even be falling apart.

With an orbital radius only 72% of the Roche limit I imagine Peggy Sue may indeed be falling apart

Code: Select all

Satellite 	 Orbital Radius/Roche limit
                 (rigid) 	(fluid)
------------------------------------------------------------
Pan 	            142% 	  70%
Daphnis            145% 	  72%
Peggy Sue          145% 	  72%
Atlas 	          156% 	  78%
Prometheus 	     162% 	  80%
Pandora 	        167% 	  83%
Epimetheus 	     200% 	  99%
Janus 	          195% 	  97%

[b][color=#0000FF]Édouard Roche (17 October 1820 – 27 April 1883)[/color][/b]

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<<The Roche limit (similar to the sound of rosh), sometimes referred to as the Roche radius, is the distance within which a celestial body, held together only by its own gravity, will disintegrate due to a second celestial body's tidal forces exceeding the first body's gravitational self-attraction. Inside the Roche limit, orbiting material disperses and forms rings whereas outside the limit material tends to coalesce. The term is named after Édouard Roche, who is the French astronomer who first calculated this theoretical limit in 1848.

Typically, the Roche limit applies to a satellite's disintegrating due to tidal forces induced by its primary, the body about which it orbits. Parts of the satellite that are closer to the primary are attracted by stronger gravity from the primary, whereas parts farther away are repelled by stronger centrifugal force from the satellite's curved orbit. Some real satellites, both natural and artificial, can orbit within their Roche limits because they are held together by forces other than gravitation. Jupiter's moon Metis and Saturn's moon Pan are examples of such satellites, which hold together because of their tensile strength (that is, they are solid and not easily pulled apart). In principle, objects resting on the surface of such a satellite would actually be lifted away by tidal forces. A weaker satellite, such as a comet, could be broken up when it passes within its Roche limit.

Since tidal forces overwhelm the gravity that might hold the satellite together within the Roche limit, no large satellite can gravitationally coalesce out of smaller particles within that limit. Indeed, almost all known planetary rings are located within their Roche limit, Saturn's E-Ring and Phoebe ring being notable exceptions. They could either be remnants from the planet's proto-planetary accretion disc that failed to coalesce into moonlets, or conversely have formed when a moon passed within its Roche limit and broke apart.>>

[b][color=#0000FF]Viktor Safronov (11 Oct. 1917 - 18 Sept. 1999)[/color][/b]

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<<A widely accepted theory of planet formation, the planetesimal hypothesis of Viktor Safronov (11 October 1917 [my mom's birthday! -ACN] - 18 September 1999), states that planets form out of cosmic dust grains that collide and stick to form larger and larger bodies. When the bodies reach sizes of approximately one kilometer, then they can attract each other directly through their mutual gravity [OR fly apart from tidal forces], enormously aiding further growth into moon-sized protoplanets. This is how planetesimals are often defined. Bodies that are smaller than planetesimals must rely on Brownian motion or turbulent motions in the gas to cause the collisions that can lead to sticking. Alternatively, planetesimals can form in a very dense layer of dust grains that undergoes a collective gravitational instability in the mid-plane of a protoplanetary disk. Many planetesimals eventually break apart during violent collisions, as may have happened to 4 Vesta and 90 Antiope, but a few of the largest planetesimals can survive such encounters and continue to grow into protoplanets and later planets.

It is generally believed that about 3.8 billion years ago, after a period known as the Late Heavy Bombardment, most of the planetesimals within the Solar System had either been ejected from the Solar System entirely, into distant eccentric orbits such as the Oort cloud, or had collided with larger objects due to the regular gravitational nudges from the giant planets (particularly Jupiter and Neptune). A few planetesimals may have been captured as moons, such as Phobos and Deimos (the moons of Mars), and many of the small high-inclination moons of the giant planets.>>

[MargaritaMc]

The Icarus article can be found here:
http://dx.doi.org/10.1016/j.icarus.2014.03.024
The discovery and dynamical evolution of an object at the outer edge of Saturn’s A ring
Carl D. Murray, Nicholas J. Cooper, Gareth A. Williams, Nicholas O. Attree, Jeffrey S. Boyer