‘Mysterious Flying Whirlpool’ in the Sky Was Not a UFO – CNET [CNET]

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The whirlpool shows up in the video as a swirl flying in from the left and slowly disappearing toward the horizon. The telescope team joked about keeping the origin of the UFO a mystery, but then said it seemed to actually be the falling second stage of a SpaceX Falcon 9 rocket. 

SpaceX launched the NROL-85 mission on April 17 from Vandenberg Space Force Base in California. The first stage of Falcon 9 is safely brought back down for reuse while the second stage takes the payload to orbit. The second stage — a disposable part of the rocket system — usually comes back to reenter Earth’s atmosphere over the ocean.

Dutch scientist Marco Langbroek tracks satellites and chimed in on the why the second stage looked like a whirlpool, tweeting that the spiral shape is often seen when a Falcon 9 vents propellants.

SpaceX has been launching missions at a rapid clip this year. The telescope team called the whirlpool sighting rare, but there could be more of these fun views caught on camera as Falcon 9 launches become ever more routine.