In Reply to: Huh? posted by mh on September 30, 2026 at 12:40:36
For the first time in its history, the Very Large Telescope in Chile is operating with up to seven lasers that fire up into the atmosphere. But why do astronomers need them?
If you happened to be wandering Chile's Atacama Desert in the middle of the night, you might encounter an extraordinary scene: the sight of enormous lasers piercing the sky. From a distance, you'd see them emerging from a sci-fi structure on a mountain top, like the lair of an evil villain.
Closer up, though, you'd discover the source is actually a telescope – a particularly big one – made up of several buildings. Inside, teams of astronomers on the night shift would be positioning the lasers to create an "artificial star" at the edge of Earth's atmosphere.
If you were passing by this evening, you might catch them firing four lasers from four separate structures on the mountain-top at the same time – which would be a first.
This is the Very Large Telescope (VLT) at Paranal – operated by the European Southern Observatory (Eso) – which the BBC recently visited. In late 2025, engineers there finished installing the last of a series of powerful new lasers to help astronomers peer into the cosmos with greater fidelity, taking the total number to seven. But why do telescopes need such lasers in the first place?
The idea for using lasers in astronomy can be traced back to the Cold War, when the US military developed technology to track Soviet satellites. Astronomers eventually realised that similar techniques would help improve their observations from the ground.