The universe is a space that prompts questions; questions such as what exactly happens at the centre of a galaxy? Andrea Ghez, winner of the 2020 Nobel Prize in Physics, has dedicated herself to this very question throughout her career as astronomer and astrophysicist. Could it actually be possible that at the core of every galaxy lies a supermassive black hole that gets more massive the more massive a galaxy is? These are the types of questions discussed and researched in astronomy.
Although the scientific community acknowledges the existence of black holes, their nature remains a mystery. Basic research is yet to come up with any kind of logical explanation for how “supermassive black holes” were formed, what they are made of, and what part they play in the emergence and evolution of entire galaxies. According to one common theory, they may have been created by the fusion of what were once stellar black holes. The latter emerge when massive stars collapse. Of course, this assumption has yet to be verified or refuted on the basis of tangible measurement data.
From a possibility to certainty
In the case of our galaxy, the Milky Way, it is now generally accepted, both theoretically and empirically, that a supermassive black hole exists at its centre. Its name is Sagittarius A*. Reinhard Genzel, Director of the Max Planck Institute for Extraterrestrial Physics, and Andrea Ghez, Professor of Physics & Astronomy at the University of California, Los Angeles, have provided the most conclusive empirical evidence of its existence to date. Next week, Ghez will talk about the journey “from a possibility to a certainty of a supermassive black hole” as part of the Paul Bernays Lectures 2021. She will also discuss the extent to which lessons learned from the Milky Way might broaden our knowledge about other galaxies.
Ghez shared the 2020 Nobel Prize in Physics with Reinhard Genzel and Roger Penrose: Penrose for discovering that the formation of black holes is a robust prediction of the general theory of relativity; Genzel and Ghez for discovering a supermassive compact object at the centre of our galaxy. From a physical perspective, black holes are actually immensely compact objects with an extremely high mass and a force of gravity so strong that they pull in anything that finds its way into their entry area, known as the event horizon. Nothing can escape from a black hole, neither stars nor suns, radiation nor information – not even light. The fact that they “swallow up” light and remain invisible to humans is what gives black holes their name.
