#light_year__lightyear  the distance that light travels in a vacuum in 1 year; 5.88 trillion miles or 9.46 trillion kilometers
  supertype:  astronomy_unit__astronomyunit  a linear unit used for astronomical distances
  part:  light_hour__lighthour  the distance light travels in a vacuum in one hour; approximately one billion kilometers
  part:  light_minute__lightminute  the distance light travels in a vacuum in one minute; approximately 18 million kilometers
  part:  light_second__lightsecond  the distance light travels in a vacuum in one second; approximately 300,000 kilometers

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