Manne Siegbahn Memorial Lecture

A Massive Accreting Black Hole at the Center of the Milky Way!

At a distance of only ~26400 light years the Galactic center is the closest ‘quiescent’ galaxy nucleus that we can now study in unprecedented detail. Over more than 10 years proper motions and orbits of individual stars in the central stellar cluster have been observed using speckle and adaptive optics techniques at the ESO NTT and the VLT.

Recently the unique equipment in combination with the advantages of the ESO Paranal site (excellent seeing, GC passes close to Zenith), make the VLT the ideal instrument for studying the extremely dense GC stellar cluster and the immediate environment of the compact radio source SagittariusA* (SgrA*) at ist center.

Observations of the orbit of star S2 have provided new, highly significant evidence that the central non-thermal radio source SgrA* is indeed a super-massive black hole with a mass of 3-4 million solar masses. The recent detection of quiescent emission and powerful flare activity of SgrA* in the X-ray and near-infrared domain have strengthened the case for an accreting massive black hole even further.