The asteroid 486958 Arrokoth was discovered to be binary by astronomers lugging a bunch of telescopes around (I think) camping with them. The timing offered additional astrometry for the orbit determination before New Horizon's flyby, and it also served to put an upper limit on any dust or debris cloud around the object that might suggest a farther flyby distance be considered.

Their hard work certainly paid off and an outline of the object was reconstructed, showing that it was likely a binary; two circular objects. This posed a bit of a mystery because there wasn't any periodic variation in brightness detected that would suggest rotation, but that's a different story.

Is this the only solar system object that was discovered to be binary (or higher) via occultation?

enter image description here

above: reconstructed occultation timing from several nearby sites from this answer below: series of images from New Horizons during flyby from this question

1.3 MB GIF: https://i.stack.imgur.com/Ci213.gif also viewable in YouTube

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    $\begingroup$ I'd suggested removing the animation. It does little for the question and it's a megabyte in size, which is a bit rough for people without good internet connections (and lots of people still have poor internet bandwidth). $\endgroup$ – StephenG Mar 10 at 16:09
  • $\begingroup$ @StephenG okay doing so now. $\endgroup$ – uhoh Mar 10 at 16:14
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    $\begingroup$ Buie et al. 2020 give lots of detail on the Arrokoth campaign but don't say much about other targets. $\endgroup$ – Mike G Mar 10 at 17:40
  • $\begingroup$ @MikeG Thanks! It's quite a thorough write-up. I'm sure there haven't been very many campaigns involving such a choreographed deployment of portable telescopes, but it's possible a photometric "double-dip" seen from one fixed location in the same way that Neptune's rings were first detected in 1968 (thought not appreciated at the time). For the purposes of this question ring discovery won't count towards the object being "binary". $\endgroup$ – uhoh Mar 10 at 23:43
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    $\begingroup$ Presumably not the only one, but KBO occultations are a fairly new trick only possible thanks to the Gaia DRs. $\endgroup$ – AtmosphericPrisonEscape Mar 12 at 11:10

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