The galactic center, imaged in infrared by the Spitzer space telescope [NASA/JPL-Caltech]

The History of the Discovery of Sgr A*

At the center of the Milky Way hides a four-million solar mass black hole. The confirmation of its existence, which took place thanks to the study of star orbits conditioned by its immense gravity, earned the Nobel Prize 2020 for physics to Andrea Ghez and Reinhard Genzel. But the story of the observations that led to the discovery of this supermassive black hole begins in the 1950s and deserves to be told

A powerful radio source towards the Galaxy’s darkened center

In 1968, Eric E. Becklin and Gerald Neugebauer, two Caltech astronomers, managed to scan the central parsecs of the Milky Way in four different infrared wavelengths, obtaining the best results at 2.2 µm. Overcoming 25 magnitudes of obscuration due to the dust in the interposed spiral arms, they discovered swarms of stars huddled together with an unlikely density, compared to the enormous distances that, in the galactic periphery, separate the Sun from its neighbors. An article published in Scientific American in April 1974 (R.H. Sanders and G.T. Wrixon, “The Center of the Galaxy”)…