GRAVITY is the second-generation VLTI instrument for precision narrow-angle astrometry and interferometric imaging. It will bring 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 will push the sensitivity and accuracy far beyond what is offered today. Providing precision astrometry of order ten microarcseconds, and imaging with four milliarcsecond resolution, GRAVITY will revolutionize dynamical measurements of celestial objects: it will probe physics close to the event horizon of the Galactic Center black hole, unambiguously detect and measure the mass of black holes in massive star clusters throughout the Milky Way, uncover the details of mass –accretion and jets in young stellar objects and active galactic nuclei, and probe the motion of binary stars, exoplanets and young stellar disks.
ESO Press release: GRAVITY Instrument Breaks New Ground in Exoplanet Imaging
Press release: First Galactic Center Observations
GRAVITY had First Light in January 2016
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: