Reinhard Genzel | PAS Academician

The black hole at the center of our Galaxy

Proving that massive black holes do exist in the Universe has been a stepwise process. As compared to forty years ago, measurements have pushed the ‘size’ of the 4 million solar mass concentration in the Galactic Center downward by a factor of almost 10^6, and its density up by 10^18. Looking ahead toward the future, the question is probably no longer whether SgrA* must be a massive black hole, but rather whether general relativity is correct on the scales of the event horizon, whether space-time is described by the Kerr metric and whether the ‘no hair theorem’ holds. Further improvements in technology, most notably of the European Southern Observatory VLT interferometer GRAVITY (to GRAVITY+) and the next generation 25-40m telescopes (the ESO-ELT, the TMT and the GMT), promise further progress. A test of the no hair theorem in the Galactic Center might come from combining the stellar dynamics with EHT measurements of the photon ring of SgrA*.

The full text of this forty-year journey can be found in my Nobel lecture.