The disorder observable at the outer edge of Saturn's A ring in this image from NASA's Cassini spacecraft might be produced by an object replaying the birth procedure of icy moons.
Image Credit: NASA/JPL-Caltech/Space Science Institute
Astronomers may have just observed the birth of a small, icy moon inside the rings of Planet Saturn. As scientists think that it might be Saturn’s last natural satellite, this birth of new moon is a precious and mainly rare occasion for astronomers and scientists, to learn about the creation of the planet’s many moons, including the ocean-holding Enceladus and the cloud-wrapped moon Titan.
Precisely one year ago, a fine angle camera on NASA's Cassini spacecraft by chance documented disturbances at the very brink of Saturn's ring, the outmost of the rings. One of these recorded disturbances is an arc, which is about 1,200 kilometers long and 10 kilometers wide, that was about 20 percent brighter than its surroundings. There is also indication of “unusual protuberances” in the typically smooth shape at the ring's brink.
Scientists think protuberances and the arc are triggered by the gravitational effects of a close object. "We have not seen anything like this before," Carl Murray from Queen Mary University of London says in a news announcement. "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."
The findings were distributed in Icarus.
Named Peggy after Murray’s mother-in-law, this icy object is maybe no more than a kilometer in diameter, making it too small to be seen in images right now. Picture above is exactly what scientists have seen and it is indication of disorder at the ring’s edge supposed to be triggered by Peggy’s occurrence.
Planet Saturn so far has 53 official moons and 9 impermanent ones. They usually range in size depending on their closeness to the planet: The farther from the planet, the bigger. Many of the planet’s moons are composed mainly of ice just like the particles that form its rings, scientists consider that the icy moons made from ring particles and then stirred outward. The eldest moons formed when these rings were more extensive, combining and becoming larger as they compound with other moons on the way; these likely drifted into orbits beyond the planet. “The theory holds that Saturn long ago had a much more massive ring system capable of giving birth to larger moons," Murray says. "As the moons formed near the edge, they depleted the rings and evolved, so the ones that formed earliest are the largest and the farthest out."
Newer moons, like this new one, tended to be smaller and stayed closer. It is also thinkable that the process of moon creation in Saturn's rings finishes with Peggy, as the rings are probably too exhausted now to create more moons. The scientists don’t expect Peggy to develop any bigger, they think it’s actually falling apart.
NASA's Cassini spacecraft’s orbit will move closer to the outer edge of the ring in late 2016, providing scientists a nearer look at the baby moon, and possibly a chance to image it. The findings might also offer understanding into how Earth and other planets made and travelled away from the sun.
[NASA JPL via Los Angeles Times, Slate]
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