According to a CNRS publication dated November 18, 2025, based on a press release from the ESO (European Southern Observatory). On November 10, four lasers simultaneously pierced the sky at Cerro Paranal in Chile, marking a major milestone in the GRAVITY+ project, to which the Lyon Astrophysics Research Center (CRAL / OSUL – Sponsored by: CNRS / ENS de Lyon / Université Claude Bernard Lyon 1). Photo: Artist's rendering of the GRAVITY+ project on the VLT © ESO
On November 10, 2025, four lasers simultaneously pierced the sky at Cerro Paranal in Chile, marking a major milestone in the GRAVITY+ project. This spectacular upgrade of the Very Large Telescope Interferometer (VLTI) opens up the entire southern sky to observations and increases the power of the GRAVITY instrument tenfold. Several CNRS Earth & Universe research teams are heavily involved in this international project led by the Max Planck Institute in Garching.
Shot from each of the four giant 8-meter telescopes of the Very Large Telescope (VLT), these laser beams create artificial stars at an altitude of 90 kilometers. These reference stars enable the adaptive optics system to measure and correct in real time the blurring caused by the Earth's atmosphere. A deformable mirror located in each telescope is adjusted several thousand times per second, compensating for atmospheric disturbances and enabling observations with a sharpness comparable to those made from space.
Until now, adaptive optics required pointing at bright reference stars close to the target, limiting the number of observable objects. Thanks to the installation of a laser on each of the four unit telescopes, completed over five years, atmospheric turbulence can now be corrected anywhere in the sky, transforming the VLTI into the most powerful optical interferometer in the world. The VLTI combines the light from several telescopes using interferometry, achieving a level of detail equivalent to that of a giant telescope with a diameter equal to the distance between the telescopes.
This technological breakthrough realizes a vision formulated in 1986 in the final report of the Very Large Telescope Project: “If it could work in practice, it would be a revolutionary advance.”
The installation of these laser stars, coupled with the recent upgrade of adaptive optics systems, significantly increases the amount of light collected and transmitted, making the facility up to ten times more sensitive. GRAVITY+ is thus ushering in a visual revolution that heralds an astronomical revolution, achieving unprecedented sensitivity and integration depth at such angular resolution.