On April 20, 2007, just after Encke had crossed the orbit of Mercury, it was hit by a CME that completely ripped off its plasma tail – a phenomenon known as a disconnection event (DE). While that has surely happened to comets before, for the first time instruments aboard a spacecraft were watching: Thanks to a fortuitous alignment with the STEREO-A spacecraft, its Sun-Earth Connection Coronal and Heliospheric Investigation (SECCHI) Heliospheric Imager-1 (HI-1) was able to finally record a movie of a DE.

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