saturn’s strangest ring

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Saturn’s Strangest Ring. Carl Murray (Cassini ISS Team Member) with help from Kevin Beurle, Nick Cooper, Mike Evans, Gareth Williams and Carlos Chavez Astronomy Unit Queen Mary, University of London. CHARM Telecon. May 25th, 2010. 1. PIA09803. Outline. - PowerPoint PPT Presentation


  • *Saturns Strangest RingCarl Murray(Cassini ISS Team Member)

    with help from Kevin Beurle, Nick Cooper,Mike Evans, Gareth Williams and Carlos Chavez

    Astronomy UnitQueen Mary, University of LondonCHARM TeleconMay 25th, 2010*

  • *PIA09803

  • *OutlinePioneer 11, Voyager and HST observations of the F ringCassini observations of the F ringObjects in the vicinity of the F ringThe effect of PrometheusEvidence for embedded objectsConclusions

  • *ABCD*

  • *Pioneer 11 imageGehrels et al. (1980)

  • *Pioneer 11 charged particle dataSimpson et al. (1980)

  • *Voyager 1 image showing:braidsclumpskinks

  • *Voyager 1Nov 1980Voyager 2Aug 198112a2b345Murray, Gordon & Giuliatti Winter (1997)

  • *August 1981February 1994Murray & Giuliatti Winter (1996)PIA07549PIA07632PandoraPrometheusdifferential precession

  • *Giuliatti Winter, Murray & Gordon (2000)Showalter & Burns (1982)ahkGravitational effect of close satellite

  • *Showalter (2004)Tracking clumps in the F ring

  • *

  • *(McGhee et al. 2001)Ring Plane CrossingObservations

  • *S/2004 S 3S/2004 S 6June 2004October 2004= S/2004 S 4?

  • *2005 DOY103 Detectionstypically~90detectionsofeachobject

  • *2005 DOY121 Detectionstypically~6detectionsofeachobject

  • *2005 DOY123,4 Detectionstypically~6detectionsofeachobject

  • *Cassini VIMS and UVIS Occultationof the F Ring (Alpha Sco Egress)Pywacket(479m)Esposito et al. (2007)Evidence for Additional Objects Near F Ring Core13 objects detected, all within ~10km from core;mostly semi-opaque; sizes in the range 30m 9km

  • *WACNACPrometheusCassini SOI images

  • *Production of streamers and channels by Prometheus

  • *2005 DOY103

  • *2005 DOY103 FMOVIESheared channels in F ringPr

  • **Frame is moving with the average speed of PrometheusSimulation of Prometheus interacting with the F ring

  • *The perturbing effect of PrometheusMurray et al. (2005)

  • *Comparison of simulation with Cassini imagesMurray et al. (2005)

  • *Prometheus perturbing the F ringISS_033RF_FRSTRCHAN001_PRIME


    sequence of images at near-constant inertial longitudesequence of images at various inertial longitudesTwo Ways To Obtain Longitudinal Coverage

  • *Spiral structure of F ring strandsCharnoz et al. (2005)*

  • *Sample Mosaic of F Ring (2005 DOY103)Co-rotating with F Rings mean motion03600-750+750Co-rotating Longitude (deg.)Epoch 12h UTC 1st January 2007Radial Offset (km)1492

  • *Colwell et al. (2009)

  • *Cassini ISS F Ring Longitudinal Coverage 20052007

  • *Major event in F ring between 2006 DOY329 and DOY357N1545564642PIA08863N1545564642N1545564196Reprojected Images8.51500kmradial motion ~200 km/h outwardsEvidence for Larger Objects Near the F ring

  • *2005 DOY1722005 DOY180Detections of S/2004 S 6

  • *15432006-329

  • *15452006-357

  • *Radial Offset (km)Co-rotating Longitude2007-0052007-0412007-0582006-357Passage of S/2004 S 6Murray et al. (2008)

  • *Radial Offset (km)Co-rotating Longitude2007-0902007-1082007-1252007-076Passage of S/2004 S 6Murray et al. (2008)

  • *Comparison of mosaic with jet simulationsMurray et al. (2008)

  • *15552007-10814922005-103Gross features of F ring are similarto those that existed 2 years previously=> Caused by same object?*

  • *N1538169712N155287157N1557039476Evidence For Embedded Objects in Core(examples of fans)*

  • *Effect of embedded satellite on circular orbithorseshoe zonechaotic zonepassing zoneMurray & Dermott (1999)

  • *5km satellite on circular orbit at edge of 50km-wide ring

  • *5km satellite on 4 eccentric orbit at edge of 50km-wide ring

  • *N1537876778Embedded object on eccentric orbit perturbs adjacent material which acts like a tracer for the gravitational effect of the object entirely analagous to the mechanism by which Prometheus creates channels in the F ringComparison of image with integrationMurray et al. (2008)

  • *PIA09782Reprojected image showing fans

  • *PIA08290

  • *Embedded satellite plus Prometheus conjunction

  • *PIA10593Prometheus

  • *Chavez (2009)Numerical simulation

  • *ConclusionsThere exist several hundred small (radius