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Abstract |
the existence of black holes has been predicted for a long time, even before general
relativity was sketched by Albert Einstein. Their extreme compactness makes them difficult
to explore on spatial scales close to the event horizon. Sagittarius A*, at the center of the
Galaxy, is the black hole with the largest angular size. A collaboration of European
astronomers has built the GRAVITY instrument for the Very Large Telescope Interferometer
of ESO to test the black hole nature of Sgr A* thanks to observations in the infrared at
unprecedented spatial scales. General relativity can consequently also be tested at these
scales in an extreme regime of gravity. I will present the results we have obtained with the
star S2, the closest star known to Sgr A*. I will also present the first results on infrared
flares occurring near the event horizon. I will conclude on the promising prospects of GRA |
