Powerful laser is 'brightest light in the universe'
By David Shiga (Image: Texas Petawatt Laser/University of Texas) 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. A petawatt is 1 million billion watts, far more than the output of all the world’s power plants put together, which is measured in mere terawatts (1 terawatt is a trillion watts). The Texas Petawatt Laser produced a pulse with more than 1 petawatt of power for the first time on 31 March. In the 1990s, the Petawatt laser at the Lawrence Livermore National Laboratory in California, US, part of a now-defunct laser facility called Nova, achieved pulses of more than 1 petawatt, but it is no longer in operation. The operators of the Texas Petawatt Laser are slowly ramping up the laser’s power. The device’s director, Todd Ditmire of the University of Texas in Austin, says he expects to smash the Livermore laser’s record within a few weeks and to eventually produce pulses of 1.4 petawatts. The energy contained in each laser pulse is only about 200 joules, about as much as a light bulb consumes in a few seconds. But this modest amount of energy is packed into a very brief pulse just one-tenth of a trillionth of a second long, which makes it vastly more powerful than any light bulb. The awesome power of the laser can be focused on a spot just one-tenth the width of a human hair, producing a light intensity higher than anything that has occurred in the universe since the big bang. The most intense natural sources of light currently known in the cosmos are gamma-ray bursts, which occur when some massive stars collapse to form black holes or neutron stars, setting off powerful explosions as they do so. “My astrophysicist friends tell me that near a gamma-ray burst, they surmised that the [light] intensity probably gets to 1020 watts per square centimetre during the explosion,” Ditmire told New Scientist. Light from the Texas Petawatt laser can reach about 100 times that level, he says. “For the briefest instant, over a very small volume, we’ll have the brightest light in the universe.” Scientists can produce extreme conditions by firing the laser at puffs of gas inside a vacuum chamber, experiments that will help them understand some of the most exotic environments in the universe. When the laser hits the gas cloud, it unleashes a shock wave similar to those seen when stars die in supernova explosions. Supernova shock waves can nudge nearby gas clouds, triggering them to collapse and form stars. Such experiments can also help scientists probe the interiors of gas giant planets like Jupiter as well as the innards of objects called brown dwarfs, which are gaseous orbs more massive than planets but not heavy enough to sustain the nuclear fusion that stars do. A laser pulse fired at a piece of material like aluminium briefly heats it to millions of degrees Celsius and raises its pressure to about 1 billion times that at sea level on Earth, similar to the extreme conditions inside gas giants and brown dwarfs. The experiments could help scientists learn how easily this exotic matter conducts electricity, which could shed light on the magnetic fields produced by the objects. The experiments could also help scientists better understand gamma-ray bursts. Some scientists say the extremely high temperatures present in gamma-ray bursts should lead to the production of antimatter, a phenomenon that might be replicated by the Texas Petawatt Laser. “It’s surmised that we can actually create a small amount of matter-antimatter plasma in the lab with the petawatt laser,