Physicists have turned on the world's most powerful laser, whose pulses are more intense than any known light source in the universe. The incredible temperatures and pressures it generates when it hits a target will let scientists explore conditions found in exploding stars and the cores of giant planets. The Texas Petawatt Laser resides at the University of Texas in Austin, US. It can blast out infrared laser pulses that each have more than 1 petawatt of power.