Scientific prospects for VLTI in the galactic centre: Getting to the Schwarzschild radius

Abstract

The centre of our Galaxy is by far the closest galactic nucleus to the Earth. Not surprisingly, Sgr A*, the super-massive black hole candidate lying at its gravitational centre, is the black hole (BH) candidate which offers the best spatial resolution in terms of Schwarzs child radius RS, thanks to the good compromise between its mass (≃3.6 ×106 M⊙) and distance (≃8 kpc). For a 3.6 × 106 M⊙ BH, RS = 14 R⊙ (≃ 8 μas at 8 kpc). This is still two orders of magnitudes smaller than the spatial resolution offered by the VLTI, but it is the right scale for studies involving only astrometry with PRIMA. We will show how this property can be used to tremendously improve the knowledge of the central mass distribution, constrain the properties of the BH, and even directly probe the space-time around this object. © 2007 Springer.