From: keel@bildad.astr.ua.edu   
      
   AlexT  wrote:   
   > Folks   
      
   > Reading through various articles about the upcoming launch of the New   
   > Horizon probe I did not manage to locate any solid information about   
   > the amount of energy & light available from the Sun on Pluto.   
      
   > I remember having read something like "about the size and brightness   
   > of Venus as seen from earth".   
      
   > If it's true I find it really remarkable that an earth based   
   > telescope would manage to "see" Pluto...   
      
      
   In 2012, for example, Pluto will be 32.2 times as far from the Sun   
   as we are, so sunlight will be 32.2^2 = 1037 times weaker than   
   we see it. That means it still delivers 1.3 W/meter^2. The sun   
   wojld still apear quite bright; that would make it apparent   
   magnitude -18.5, which is still 250 times as bright as our   
   view of a full Moon. That's plenty of light to see your way   
   around or get good images (and it's not all that much less light   
   than Voyager 2 had to deal with at Neptune and Triton).   
      
   Bill Keel   
      
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