GRAVITY: getting to the event horizon of Sgr A*

Understand

We present the second-generation VLTI instrument GRAVITY, which currently is in the preliminary design phase.

• GRAVITY is specifically designed to observe highly relativistic motions of matter close to the event horizon of Sgr A*, the massive black hole at center of the Milky Way.
• We have identified the key design features needed to achieve this goal and present the resulting instrument concept.
• It includes an integrated optics, 4-telescope, dual feed beam combiner operated in a cryogenic vessel; near infrared wavefront sensing adaptive optics; fringe tracking on secondary sources within the field of view of the VLTI and a novel metrology concept.