Just some numbers for those who think about diverting the asteroid by pumping energy into it.

Assumptions:

 - $60$ km diameter, same as https://en.wikipedia.org/wiki/Chicxulub_impactor
  - $113097 km^3$ volume
 - [$2g/cm^3$ density][1], 
 - [$2.262*10^{17}kg$ source][2], 
 - If we impart an impulse in 3 months(ie. 9 months before impact) we need a delta-v of $0.27m/s$.
 - [This will take $2.944*10^{8}TJ$][3].
  - Or about 75 times the total energy yield of all nuclear bombs detonated to date.
  - This does not include the energy needed to get a bomb to the asteroid.

Edit:

Other aritcles on wikipedia gives an estimate of 10km as the diameter of the asteroid.  This reduces the energy needed to divert it by a factor of 216, meaning we would need the energy of between 3 and 4 Tsar Bombas to divert it.

  [1]: https://en.wikipedia.org/wiki/Standard_asteroid_physical_characteristics#Density
  [2]: http://www.wolframalpha.com/input/?i=113097%20km%5E3*2g%2Fcm%5E3
  [3]: http://www.wolframalpha.com/input/?i=2.262*10%5E17kg%28%2827m%2Fs%29%5E2%29%20in%20TJ