Interferometry: GRAVITY+

The Very Large Telescope (VLT) at the European Southern Observatory (ESO) is an array of four “large” telescopes with a diameter of 8.2 m and four “small” telescopes with a diameter of 1.8 m. It is possible to coherently combine the light from several telescopes in order to obtain spatial resolution ? equivalent to that which would be produced by a single telescope with a mirror, the diameter of which is given by the distance between the individual telescopes, i.e. up to 200 m. This technique is called interferometry. The GRAVITY+ instrument, installed on the VLT in 2024, can be used to observe the neighbourhood of very bright sources. It can for example combine the radial velocity ?  and direct detection methods, to obtain both mass and temperature and thus gain a clearer understanding of how exoplanets formed.

Parameters (semi-major axis ? , mass) of the planets observable with GRAVITY+ between the observability ranges of Gaia and imaging.
LIRA
Aerial view of the VLT with the four 8.2m telescopes, which can observe individually or in interferometric mode. The four 1.8m auxiliary telescopes are mobile and dedicated to interferometric observations.
J.L. Dauvergne & G. HĂŒdepohl (atacamaphoto.com)/ESO
Moonrise and mountain shadow on the clouds in the Atacama desert
(Anthony Berdeu)