Reinhard Genzel is the man who revealed the supermassive black hole at the very centre of our own galaxy, the Milky Way. The evidence gathered by his research group in Germany and by a group led by Andrea Ghez in California is now so compelling that there is no longer a debate among astronomers that black holes really exist. In 2008 Genzel received the Shaw Prize in Astronomy for this work. The Shaw Prize is one of the most prestigious in all of science.
As long ago as the 1970s some astronomers began to suspect that a very large black hole could be lurking in the centre of the Milky Way, but it was generally felt that it would be too difficult to prove. Reinhard Genzel thought differently. Working for 20 years, he developed new kinds of astronomical cameras and then used them to do time-lapse photography of stars at the very centre of the Galaxy. His determination and patience finally paid off in 2002, when he could prove that the central stars were moving so fast that only the extremely strong gravity of a black hole having the mass of millions of Suns could keep them on their orbits.
Expert in submillimetre astronomy, its instruments and techniques
Genzel has played an important role in the development of infrared and submillimetre astronomy. To reveal the central black hole, Genzel and his group needed to develop new technologies for making ultra-precise observations of the positions of stars. They deployed their cameras on the telescopes of the European Southern Observatory (ESO) in Chile. Since then, the instruments and techniques he and his teams have developed have become standard, and are widely used all over the world.
There is more to discover
The discovery of the black hole has, of course, led to many more observations and discoveries. Although normally no light can be seen coming from the black hole itself, Genzel and his team have seen occasional flares - spectacular releases of energy – emitted by gas that is just about to fall into the black hole. By observing these flares in detail, Genzel's team has provided strong evidence that the black hole is rotating, again in accord with Einstein’s theory. Other astronomers are examining the effect of the central black hole on the whole cluster of millions of stars around it. They are trying to solve the biggest mystery of all: how the stars that Genzel photographed got there in the first place! Many of them are so young that they probably formed very near the central hole, but there is no evidence for stars forming now, or for the gas from which they should have condensed.
In his Interview with Annalie, Reinhard Genzel tells the whole story of this exciting discovery.
How interest became passion, which drove hard work, which led to a breakthrough
During his time as a young scientist at the University of California in Berkeley, Reinhard Genzel first became interested in proving that there is a giant black hole in the centre of the galaxy. Not many others were convinced at that time, however. Genzel knew he needed to observe the motions of the central stars, but most astronomers felt that the stars would be too dim to see, and even if seen their motions could not be measured precisely enough.
After moving to the Max Planck Institute for Extraterrestrial Physics in Garching near Munich, Genzel focused his research on this idea and started to develop very sophisticated technology for observing the orbits and velocities of stars in the centre of our galaxy. Because visible light from the centre of our Galaxy is blocked by interstellar dust, Genzel knew he had to observe in infrared light or even at the longer wavelengths of the submillimetre spectrum. He had to work hard to convince the astronomers who allocate observing time on the biggest telescopes that, with his infrared cameras, he had a good chance of succeeding. The European Southern Observatory (ESO), one of the largest in the world, gave him regular observing opportunities on their telescopes in Chile. Finally, in 2002, years of painstaking measurements were crowned by a series of the sharpest and 'deepest' images of the Milky Way Centre ever taken. They confirmed Genzel´s prediction and opened a new field of research.
How he became an astronomer
Astronomy and physics are not the only passions in Reinhard Genzel´s life. He is also very interested in history and archaeology, and he is engaged in sports, "to balance his normal work" as he says. When he was younger, he was one of the best javelin throwers in Germany, and even trained for the national German track and field team before the 1972 Olympics.
Following study at the universities of Freiburg and Bonn, where he got his PhD, Reinhard Genzel worked at the giant Effelsberg radio telescope near Bonn, which had recently been built for the Max Planck Institute for Radio Astronomy. Later, he moved on to the Harvard-Smithsonian Center for Astrophysics in the USA, and then to the University of Berkeley, California to do research in the group of Nobel laureate Charles Townes.
Since 1986 he has been a Director at the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching, near Munich. That is where Annalie met him for our interview.
Reinhard Genzel has received many prizes for his work, including the Shaw Prize for Astronomy in 2008, the Leibniz Prize from the German Research Foundation in 1990 and the Presidential Young Investigators Award from the US National Science Foundation in 1984.
Shaw Prize Foundation
Reinhard Genzel et al., A Star in a 15.2-Year Orbit Around the Supermassive Black Hole at the Centre of the Milky Way, 2002, Nature 419, 694
MPG/MPE submillimetre astronomy and infrared astronomy group