jupiter (galileo)saturn (cassini) uranus (hubble)neptune (voyager)
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Jupiter (Galileo) Saturn (Cassini)
Uranus (Hubble) Neptune (Voyager)
Everything You Need to Knowabout Ring Dynamics
• Newton: Force = Mass x Acceleration
• Law of Gravity
• Collisions
• Light-scattering Physics
Main ring
Dark side = High “phase angle”: emphasizes tiny dust grains
“Halo”
“Gossamer ring” discovery
Two “Gossamer” rings
Dusty rings must be sustained by source bodies(seen or unseen)
A B C
Encke Gap Cassini Division
D F
Lit side = Low “phase angle”: emphasizes large bodies
EG
Enceladus
Earth!
Unique high-phase view!F
“Geysers” on Enceladus= the source of the E ring
Cassini On-line Resources
• Cassini Main Site– http://saturn.jpl.nasa.gov/
• The latest raw images (cool!)– http://
saturn.jpl.nasa.gov/multimedia/images/raw/index.cfm
• Imaging Team Web Site– http://ciclops.org/
The “Opposition Surge”on Saturn’s rings.
This appears exactlyopposite to the directionto the Sun, at phaseangle 0°.
The size of the surge isa measure of how rough the particles are.
gammaeta
lambda
epsilon
beta
alpha
6, 5, 4
delta
The main rings of UranusImaged by Voyager 2
Low phase = big particles
The rings of Uranus at high phase > dust belts!
Uranus in HST
Long exposures reveal rings
Overlaying frames shows moons
Processing shows new rings!
Mab & the mu ring
nu ring
Liberté
FraternitéEgalité
Courage
Leverrierring
Adamsring
Neptune’s Changing Arcs
• The arcs can now be detected by Hubble and ground-based telescopes.
• Since 1989, the leading arcs have advanced forward and faded.• Gravity effects of the nearby moon Galatea help to confine the
arcs– …but the model is in trouble!
Fun with Rings (1)
Vertical Ripples
D ring ripples that have been winding up since 1984!
Fun with Rings (2)
Satellite “Wakes”
Wavy edge of EnckeGap suggests anembedded moon.
Colorenhancementreveals “spiral” structure.
Perturbedcentralringlet
The discoveryof Pan
in a sequenceof five
Voyager images
A spectacularview of
the Pan wakefrom Cassini
direction to Pan
Pan Imaged at Fine Resolution by Cassini
The Discovery of Daphnis in the Keeler Gap:The wake is highly distorted
Fun with Rings (3)
Saturn’s Pathological F Ring
Ophelia
Cordelia
Two moons “shepherd” theepsilon ring of Uranus
Pandora
Prometheus
Distant Voyager approach image:Is the F ring shepherded too?
A Selection of Cassini Images
Prometheus produces a “wake” pattern just like Pan
The aftermath of a ring impact?
A recent, new feature 200 km inward from the central ring
2007: A Good Yearahead for Ring Science…
Cassini Extended MissionJuly 2008–June 2010
Sample TourScience planning is proceeding.Note that this period includes the equinox on August 11, 2009!
New Horizons at JupiterFebruary 28, 2007
The first images ofJupiter from New Horizons
Range is 1 AU
Sample planned imagesduring the
New Horizons flyby
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