Free Astronomy Magazine January-February 2026

JANUARY-FEBRUARY 2026 says Antoine Mérand, an ESO as- tronomer and VLTI Programme Scientist. The VLTI combines light from several individual telescopes of the VLT (either the four eight- metre Unit Telescopes, UTs, or the four smaller Auxiliary Telescopes) using interferometry. GRAVITY+ is an upgrade to the VLTI, with a focus on GRAVITY, a very successful VLTI instrument that has been used to image exoplanets, observe stars near and far and perform detailed observations of faint objects orbit- ing the Milky Way’s supermassive black hole. GRAVITY+ also encom- passes infrastructural changes to the telescopes and upgrades to the VLTI underground tunnels, where the light beams are brought to- gether. The installation of a laser at T his photograph shows four lasers at ESO’s Paranal Observatory, each one launched from one of the four eight-metre telescopes on site. The launch of these lasers represents a significant milestone for ESO’s Very Large Telescope In- terferometer (VLTI), which combines light from these telescopes, and the GRAV- ITY+ project — a large and complex upgrade to the VLTI. With the installation of a laser at each of the eight-metre telescopes, a bright ‘fake’ star is created 90 km above Earth’s surface by each laser, enabling the correction of atmospheric blur anywhere on the sky. This unlocks the whole southern sky to the VLTI and en- hances the observing power dramatically. This long-exposure photograph was taken in early November by ESO astronomer Anthony Berdeu on a nearly full- moon night. The moon is visible on the left of the image. [A. Berdeu/ESO] each of the previously unequipped UTs is a key achievement of this long-term project, transforming the VLTI into the most powerful optical interferometer in the world. “The VLTI with GRAVITY has already en- abled so many unpredicted discov- eries, we are excited to see how GRAVITY+ will push the boundaries even further,” says GRAVITY+ Prin- cipal Investigator Frank Eisenhauer of the Max-Planck Institute for Ex- traterrestrial Physics (MPE), Ger- many, which led the consortium carrying out the upgrade. The series of upgrades has been ongoing for a few years and includes revised adaptive-optics technology — a sys-