Curious how planets can form from disks of gas and dust?
Well, the rings of Saturn are serving scientists as a living laboratory to
better understand the process.
Astronomers have been able to use the Saturn-orbiting
Cassini spacecraft to track what are believed to be half-mile wide moons
embedded in the planet’s outermost dense ring, known as the A ring. The
moonlets were found by perturbations they are creating in the structure of the
ring, which is about 30 feet thick. The moonlets’ gravitational grip is causing
1,600-foot long shoots of material above and below ring, reports Matthew
Tiscareno, a Cassini scientist at Cornell University, in this week’s issue of Astrophysical
Journal Letters.
Scientists estimate there are dozens of these extremely long
propeller-like features toward the outer edge of Saturn’s A ring and have been
tracking 11 of them for four years — the first time a disk-embedded object has
ever been tracked anywhere.
“All the moons and planets we knew about before orbit in
empty space. With this new discovery, we can now track disk-embedded moons
individually over many years,” Tiscareno said in the press release.
Similar, smaller propeller features were first found in 2006
in the middle of the A ring, an area now known as the “propeller belts.” Those
features, however, couldn’t be traced to individual objects.
“We saw a swarm in one image and then had no idea later on
if we were seeing the same individual objects,” Tiscareno said.
Watching how the moonlets’ orbits change and evolve over
time should give scientists greater insight into the formation of planetary
systems, which evolve from similar, though much larger, debris disks.
“It allows us a glimpse into how the solar system ended up
looking the way it does,” said Cassini imaging team head Carolyn Porco, with
the Space Science Institute in Boulder, Colo.
Image: Maternity bump — moonlet in tow in Saturn’s A ring. Credit: NASA/JPL/Space Science Institute.
