1I/ʻOumuamua (2017)

  • Discovery / “entry” into our awareness: Oct 19, 2017 (Pan-STARRS).
  • Perihelion (closest to Sun): Sep 9, 2017. (NASA Science)
  • Velocity: Described by NASA as ~196,000 mph (87.3 km/s) when passing the Sun; this high speed and its hyperbolic path confirm an interstellar origin. (NASA Science)
  • Size / shape / mass: NASA characterizes it as elongated/irregular and ~hundreds of feet (≈100-meter scale); mass not determined. (NASA Science)
  • Color / composition: Reddish, dark, featureless spectrum; no obvious coma detected; later measurements showed a slight non-gravitational acceleration (behaving more comet-like). (NASA Science)
  • Exit: On an unbound (hyperbolic) trajectory; headed back to interstellar space (no return). NASA notes it was last detectable in early 2018 as it receded. No NASA “exit date” is defined. (NASA Science)

** https://science.nasa.gov/solar-system/comets/oumuamua/10-things-mysterious-oumuamua/

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