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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