Laser Guide Stars Enhance Adaptive Optics at Chile’s Very Large Telescope

The European Southern Observatory (ESO) has equipped all four Unit Telescopes at the Very Large Telescope (VLT) in Chile with laser guide star systems, supporting advanced astronomical imaging and research.

Laser guide stars are produced by directing powerful lasers into the upper atmosphere, where they cause sodium atoms to emit light and create artificial reference points for telescopes. These artificial stars enable adaptive optics systems to adjust for atmospheric distortion, resulting in clearer images of celestial objects.

The VLT, located at Paranal Observatory in Chile’s Atacama Desert, is operated by ESO and consists of four telescopes, each with an 8.2-meter primary mirror. The telescopes can function independently or be combined for interferometric observations, expanding their scientific capabilities.

UT-4, also known as Melipal, has used laser guide star technology since 2016. In December 2025, the remaining three Unit Telescopes were fitted with similar laser systems, allowing all four telescopes to support the Very Large Telescope Interferometer (VLTI) and GRAVITY+ instruments.

What the numbers show

• Each VLT Unit Telescope has an 8.2-meter primary mirror
• Lasers extend approximately 90 km into the upper atmosphere
• Each laser delivers about 22 watts of power with a 30 cm beam diameter
• UT-4 began using its laser guide star in 2016; other telescopes were equipped in December 2025

The Four Laser Guide Star Facility (4LGSF) at the VLT projects four beams into the sky, each creating an artificial star at an altitude of around 90 kilometers. Since April 2016, this system has enabled more precise correction of atmospheric effects during observations.

The installation of laser guide stars on all four Unit Telescopes increases the sensitivity and sky coverage of the VLT, particularly for the VLTI and GRAVITY+ instruments. These enhancements support a wider range of astronomical research by improving image sharpness and measurement accuracy.

The ESO released a photo on February 9, 2026, showing the Milky Way above Paranal Observatory with visible laser beams creating artificial stars. The image, captured by Chilean astrophotographer Alexis Trigo, highlights the operational status of the upgraded laser systems.

Adaptive optics systems at the VLT rely on these artificial guide stars to make real-time corrections for atmospheric blurring. This technology allows astronomers to obtain sharper and more detailed images, supporting ongoing scientific studies at the observatory.

* This article is based on publicly available information at the time of writing.