Peggy is something along the border of Saturn ’s ring , a bug whose seed we ’ve never seen . Cassini took a last peep at Peggy during its Grand Finale destructive dip , adding a final small-arm to the puzzle for next investigator to rivet over when try out to understand this mysterious disruption .
27 - year Cassini project veteran Carl Murray of Queen Mary University of London recalls his first sighting of the ring bug , in early 2013 . He was examine an paradigm of Saturn ’s lunation Prometheus at the outside edge of the A - ring , designedly bring out to show the screen background stars . “ We saw this kind of prominence - ball - feature - object whatever , ” he told me last week , during the lunch breakage of the Cassini final Imaging Team meeting , as we chatted at the Huntington Botanical Gardens near Caltech .
“ We obviously wanted to know , ‘ Was it actual ? ’ ” said Murray . He and his squad quickly check previous images of the area , and now that they knew what they were looking for , they kept find that unknown , stepped - out glitch in the otherwise swimmingly - curve edge of the A - ring . “ The twenty-four hour period I found it was my female parent - in - law ’s birthday , ” Murray recalled , so he named it Peggy in her laurels . “ It seemed appropriate . ”
Soon , the squad ’s questions about Peggy dilate : “ What is it ? Where did it come from ? Where is it going ? ” he explain . “ We ’ve been track it almost ever since . ”
Murray and his co-worker realise the glitch must be due to an object embedded in the rings . “ We ’ve never actually fix the object , ” Murray said . “ All we can do is track the glitch . ”
appraise the size of it of the psychological disorder , he quickly realized it could n’t perhaps be a satisfying moon . “ It would be a monumental Titan - size moon , ” Murray explained . “ If a moon that size was there , it would be all disrupt the band . ” Instead , he estimate it must be a impenetrable cloud of debris and debris , perchance encompassing a proto - moon that has n’t yet broken free as an independent objective .
As the mysterious aim drifts closer to and further from Saturn within the ringing , it causes the bug along the outer edge to change focal ratio . “ By measuring the speed of the bug , we can quantify the orbital parameter of the physical object , ” Murray explained .
include Peggy in Cassini ’s last six image of the Saturn scheme was partially sentimental , but the spacecraft was also collecting worthful scientific information . “ Every image we get which should contain Peggy is yet another data point point that will help us understand what it is , where it is , where it ’s do from , and where it ’s going to go even when we ’re not around to take range of a function any more , ” Murray said . “ The fact that it ’s one of the last look-alike from Cassini is touching , but we ’re doing it for science . ”
But tracking an object when you do n’t know what exactly that aim is can be tricky . Cassini ’s imaging team has found Peggy time and time again , but not always where and when they expected it . “ Sometimes you see it , sometimes you do n’t , ” Murray enunciate with a suspiration .
This uncertainty made planning the final image cunning . “ We actually reach Peggy a big margin of erroneousness because it ’s a bit wayward sometimes . ” Adding to the complexness of the shot , Cassini was on the far side of the system , shoot the rings from across the planet . This means the solution was lower : at 2.7 miles per pixel , Peggy ’s characteristic glitch will only be a few hundred pel in the image .
Murray and his team stayed up former Thursday night waiting for the raw images to download . They brought everything they take to analyze Peggy right away , working off nervous Energy Department before joining others in standing vigil for Cassini ’s final second .
When I moderate in with him via email on Friday , Murray was optimistic but unsealed Cassini had successfully obtain Peggy one last meter , writing , “ I would wish to suppose that it is [ in ] the one that also contains Daphnis , ” a tiny moon of Saturn thatlies within the Keeler Gapof Saturn ’s A - band , he say , before linking me tothe naked as a jaybird double .
Kevin Gillstayed up deep on Thursday processing Cassini ’s final images for expiration on Friday morning . “ I could n’t discover Peggy in the data though I ’m still looking , ” he told me , confirming the bug is being characteristically difficult to identify . “ Peggy ’s belike there , I just have n’t found precisely where yet . ”
“ I ’m used to every day going to the calculator when the image occur down [ to ] just look for fun poppycock , like Peggy ! ” explain Murray . “ It ’s belong to take me for a while to get used not fetch to see these images every day . ”
Cassini ’s mission is done , and its raw paradigm picture gallery will never have a new update . But Murray , his postdoc , and the rest of the mission scientist still have fruitful years ahead of them poking through thirteen yr of information and endeavor to understand this beautiful , complex Saturnian system . Perhaps , they ’ll even come to understand Peggy a minuscule bit better .
Saturn
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