Scientists solve planetary ring riddle

Posted: August 5, 2015 by oldbrew in research, solar system dynamics
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Saturn + rings {image credit: NASA]

Saturn + rings [image credit: NASA]


Researchers claim to have unearthed a universal ‘inverse cubes law’ relating to planetary rings, reports Phys.org.

In a breakthrough study, an international team of scientists, including Professor Nikolai Brilliantov from the University of Leicester, has solved an age-old scientific riddle by discovering that planetary rings, such as those orbiting Saturn, have a universally similar particle distribution.

The study, which is published in the academic journal Proceedings of the National Academy of Sciences (PNAS), also suggests that Saturn’s rings are essentially in a steady state that does not depend on their history.


Professor Brilliantov from the University of Leicester’s Department of Mathematics explained: “Saturn’s rings are relatively well studied and it is known that they consist of ice particles ranging in size from centimetres to about ten metres. With a high probability these particles are remains of some catastrophic event in a far past, and it is not surprising that there exists debris of all sizes, varying from very small to very large ones.

“What is surprising is that the relative abundance of particles of different sizes follows, with a high accuracy, a beautiful mathematical law ‘of inverse cubes’. That is, the abundance of 2 metre-size particles is 8 times smaller than the abundance of 1 metre-size particles, the abundance of 3 metre-size particles is 27 times smaller and so on. This holds true up to the size of about 10 metres, then follows an abrupt drop in the abundance of particles. The reason for this drastic drop, as well as the nature of the amazing inverse cubes law, has remained a riddle until now.

“We have finally resolved the riddle of particle size distribution. In particular, our study shows that the observed distribution is not peculiar for Saturn’s rings, but has a universal character. In other words, it is generic for all planetary rings which have particles to have a similar nature.”

Most of the planets in the Solar System have smaller bodies, or satellites, that orbit a planet. Some of them, such as Saturn, Jupiter, Uranus and Neptune, additionally possess planetary rings – a collection of still smaller bodies of different sizes that also orbit a planet. It is likely that planetary rings also exist beyond the Solar System.

This is an artist concept of a close-up view of Saturn’s ring particles. The planet Saturn is seen in the background (yellow and brown). The particles (blue) are composed mostly of ice, but are not uniform. They clump together to form …more

Large asteroids, such as Chariklo and Chiron, only a few hundred kilometres in diameter, are also surrounded by rings.

Professor Brilliantov added: “The rather general mathematical model elaborated in the study with the focus on Saturn’s rings may be successfully applied to other systems, where particles merge, colliding with slow velocities and break into small pieces colliding with large impact speeds.

“Such systems exist in nature and industry and will exhibit a beautiful law of inverse cubes and drop in large particle abundance in their particle size distribution.”

Original report: Scientists solve planetary ring riddle.

Summary and abstract: ‘Size distribution of particles in Saturn’s rings from aggregation and fragmentation’

Comments
  1. oldbrew says:

    Related to this probably: ‘ The inverse cube law of magnetic forces’

    http://image.gsfc.nasa.gov/poetry/activity/l23.pdf

  2. M Simon says:

    This is in effect a constant integrated volume law. The volume of 1 m objects = the volume of 2 m objects.

  3. oldbrew says: August 5, 2015 at 4:15 pm

    “Related to this probably: ‘ The inverse cube law of magnetic forces’”
    http://image.gsfc.nasa.gov/poetry/activity/l23.pdf

    Indeed! Potential is not energy, it is energy density! This can abstractly explain “why does mass exist”.🙂

  4. Bloke down the pub says:

    Given sufficient time, will the space junk orbiting the Earth sort itself out in the same way?

  5. oldbrew says:

    Bloke: the Earth probably isn’t enough of a magnet to do such a job. That’s a guess though.

    ‘If one represents Saturn’s magnetic field as produced by a simple current loop with a specified magnetic moment (see magnetic dipole), then that magnetic moment is about 600 times Earth’s, whereas Jupiter’s magnetic moment is 20,000 times Earth’s.’

    http://www.britannica.com/place/Saturn-planet/The-magnetic-field-and-magnetosphere

  6. JKrob says:

    “Given sufficient time, will the space junk orbiting the Earth sort itself out in the same way?”
    “Bloke: the Earth probably isn’t enough of a magnet to do such a job. That’s a guess though.”

    Hmmm…is that implying material in planetary rings are made up of ferrous metals & moons are not? Would that thinking apply to the Solar System planets as well (iron cores keep planets on the solar equatorial plane…where Pluto is not)?

  7. oldbrew says:

    JKrob: Wikipedia says ‘The ring particles are made almost entirely of water ice, with a trace component of rocky material.’

    Also ‘The rings show a tremendous amount of structure on all scales, some related to perturbations by Saturn’s moons, but much unexplained.’

    http://en.wikipedia.org/wiki/Rings_of_Saturn

    Saturn has the biggest and most obvious ring structure of all the giant planets, but the others do also have rings. Saturn is also the only planet whose magnetic field lines up with its axis.

    Any connection? Nobody knows, but the universal cubes law in the report seems to suggest a magnetic influence unless there’s a better idea.

    Then there are the spokes:
    ‘Until 1980, the structure of the rings of Saturn was explained as being caused exclusively by the action of gravitational forces. Then images from the Voyager spacecraft showed radial features in the B ring, known as spokes, which could not be explained in this manner, as their persistence and rotation around the rings was not consistent with gravitational orbital mechanics.’
    http://en.wikipedia.org/wiki/Rings_of_Saturn#Spokes

    Along the same lines:
    ‘Saturn is surrounded by a giant magnetic field, lined up with the rotation axis of the planet. This cannot be explained by current theories. Cassini may explain how the puzzling magnetic field of Saturn is generated.

    This magnetic field may also cause strange features in the rings called ‘spokes’. These markings fall across the rings like spokes in a wheel and may be caused by electrically charged particles caught up in the magnetic field, but there are as yet no detailed theories about them.’
    http://www.esa.int/Our_Activities/Space_Science/Cassini-Huygens/Saturn_s_magnetosphere

    One more:
    ‘Until recently, the structure of the rings of Saturn was explained exclusively as the action of gravitational forces. However as soon as ‘spokes’ were found, there was an assumption that they are connected to electromagnetic interaction, as they rotate almost synchronously with the magnetosphere of Saturn.’
    http://www.affs.org/html/studies_on_the_rings_of_saturn.html

  8. JKrob says: August 6, 2015 at 12:55 pm

    (“Given sufficient time, will the space junk orbiting the Earth sort itself out in the same way?”
    “Bloke: the Earth probably isn’t enough of a magnet to do such a job. That’s a guess though.”)

    “Hmmm…is that implying material in planetary rings are made up of ferrous metals & moons are not? Would that thinking apply to the Solar System planets as well (iron cores keep planets on the solar equatorial plane…where Pluto is not)?”

    Ferrous metals are poor indicators of a magnetic field. Try some platinum-cobalt if you wish to measure that magnetic field.

  9. oldbrew says:

    How does this work?

    ‘Dust pillars of destruction reveal impact of cosmic wind on galaxy evolution’

    ‘Cosmic wind can easily push low-density clouds of interstellar gas and dust, but not high-density clouds. As the wind blows, denser gas lumps start to separate from the surrounding lower density gas which gets blown downstream. But apparently, the high and low-density lumps are partially bound together, most likely by magnetic fields linking distant clouds of gas and dust.’ [bold added]

    http://phys.org/print357214547.html
    (press ‘cancel’ to view print version)