what planets have not yet been ventured on and how many years would it take to get to the furthest planet?

Question: what planets have not yet been ventured on and how many years would it take to get to the furthest planet?
- Keywords:
  explore,
  furthest,
  planet
Asked by kathsta910lol to Helen, Jenni, Mark, Martin, Stu on 16 Jun 2011.
- Jenni Tilley answered on 14 Jun 2011:
  
  Ask Brian Cox… 🙂
  
  Or take a look here /sportsj11-zone/2011/06/people-have-said-that-there-are-loads-of-planets-out-there-how-many-havent-been-explored
- Helen O'Connor answered on 14 Jun 2011:
  
  Beat me to it Jenni!
  I just attached this link to the ‘who is your favourite scientist’ question too as Brian Cox is one of my favourite popular scientists and explains things really well.
  http://en.wikipedia.org/wiki/Brian_Cox_%28physicist%29
- Mark Burnley answered on 16 Jun 2011:
  
  How many years would it take to get to the nearest planet? About 4 years if travelling at the speed of light, but about 40,000 years if travelling at speeds we’ve been able to reach so far. Don’t go booking a holiday there, that’s my advice!

Question: what planets have not yet been ventured on and how many years would it take to get to the furthest planet?