Coming off their divisional home win over the Texans, the Colts flew to Qualcomm Stadium for a Week 12 Sunday night game with the San Diego Chargers.  In the first quarter, Indianapolis took the lead as kicker Adam Vinatieri got a 23-yard field goal.  In the second quarter, the Chargers took the lead as kicker Nate Kaeding made a 35-yard field goal, while QB Philip Rivers completed a 39-yard TD pass to WR Vincent Jackson.  The Colts would tie the game as QB Peyton Manning completed a 13-yard TD pass to WR Anthony Gonzalez. In the third quarter, Indianapolis took the lead as Manning completed a 1-yard TD pass to RB Dominic Rhodes.  In the fourth quarter, the Colts added onto their lead as Vinatieri got a 38-yard field goal.  San Diego cut the Colts' lead to 3 as Rivers completed a 1-yard TD pass to FB Jacob Hester, and then Kaeding kicked a 47-yard field goal to tie the game.  However, Indianapolis sealed the deal as Vinatieri nailed the game-winning 51-yard field goal. By making the kick, Vinatieri redeemed himself after missing a game-winning 29-yard field goal against San Diego in the previous season.
Question: Who threw the longest touchdown pass of the first half?
Answer: Philip Rivers