The VLTI is the only array of 8-m-class telescopes that explicitly includes interferometry in its design and implementation. No other array is equipped with a comparable infrastructure. The VLTI, with its four 8 m telescopes and a total collecting area of 200 m, is the only interferometer to allow direct imaging at high sensitivity and high image quality. The VLTI is also the only array of its class offering a large field of view (2 arcseconds). GRAVITY is the first to use this unique capability, providing simultaneous interferometry of two objects. This allows narrow angle astrometry with a precision of order of 10 microarcseconds. A second new and unique element of GRAVITY is the use of infrared wavefront sensors to observe highly dust-obscured objects. GRAVITY is also the only instrument to provide phase-referenced complex visibilities, which is a major advantage for the model independence and fiducial quality of interferometric maps. The combination of VLTI and GRAVITY has revolutionized high-resolution astronomy and will be the world-leading facility for many years to come.

GRAVITY is the second-generation VLTI instrument for precision narrow-angle astrometry and interferometric imaging. It brings the most advanced vision to the VLT: with its fiber-fed integrated optics, wavefront sensors, fringe tracker, beam stabilization, and a novel metrology concept, GRAVITY pushes the sensitivity and accuracy far beyond what is offered today. Providing precision astrometry of order ten microarcseconds, and imaging with four milliarcsecond resolution, GRAVITY has revolutionized dynamical measurements of celestial objects: it probes physics close to the event horizon of the Galactic Center black hole, uncovers the details of mass accretion and jets in young stellar objects and active galactic nuclei, probes the motion of binary stars, exoplanets and young stellar disks, and resolves the images of the microlensing events.


ESO press release: GRAVITY Instrument Breaks New Ground in Exoplanet Imaging

MPE press releases:


GRAVITY instrument


Animation of the path an incoming light ray traces through the GRAVITY instrument. Note the intricate design and complex interaction of the various components for the four telescopes. For interferometry to work, the light paths have to be superposed with a precision of a fraction of the wavelength – less than 1 micrometre.



GRAVITY is being built by the following institutes:



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