Residing in Chile’s Atacama Desert, the brilliantly named Very Large Telescope (VLT) is the most advanced optical instrument on the planet. This week the European Southern Observatory (ESO) turned on one of the VLT’s most impressive features: the Four Laser Guide Star Facility, consisting of 4 22-watt lasers that shoot high into the atmosphere. The new lasers have been under development for years but the hard work has paid off and the VLT now hosts the most powerful laser to ever be used in astronomy.
The giant lasers are going to help astronomers get clearer images from space. Many of us learned the nursery rhyme about twinkling stars but stars don’t really twinkle, they just look like that to us because their light is refracted by turbulent layers in the Earth’s atmosphere. Light reaching Earth has to pass through a thick barrier before getting to us so we don’t get the best view.
This phenomena is called stellar scintillation and it’s a big problem for Earth-based astronomers. We want to see stars in the distant universe but everything is a bit blurry because of the Earth’s atmosphere. The extremely powerful lasers can help by acting as a “laser guide star”.
The lasers are fired up into the sky as if the Earth is a Death Star. They’re aimed at a single point that is used as an artificial star. The lasers excite sodium atoms in the upper atmosphere, causing them to glow. The telescope observes the glow and artificial star to measure how much the atmosphere is distorting the image. It can then make an astronomical observation and correct for the distortions, resulting in a much clearer image.
We should be excited for clearer observations and improved science but to be honest we’re probably more interested in the lasers. Just look at them.
Main image: ESO/S. Lowery distributed under CC by 4.0