Aim at the angle shown in the picture.
Power Activation Point
Activate your laser gun around the time when your bird passes through the top of the right planet. Your goal is to let the laser hit the middle metal part.
First Shot Result
The lasers bounce from the metal of impact, then bounces again from the right back to the left. This will bring down the tower at the left planet. The bird continues to hit the satellite and kills the rest of the pigs on the right planet.
Note that the lasers much bounce twice to destroy the tower on the left. You will not have enough points for three stars unless you destroy that tower. You may have to try this stage a couple of times but it is not too hard.