A supermassive black hole is lurking deep in the heart of our galaxy. Located about 26,000 light-years from the Sun, the environment of this object, called Sagittarius A*, offers a unique laboratory for testing the laws of physics in extremely strong gravitational fields. A group led by Reinhard Genzel of the Max Planck Institute for Extraterrestrial Physics has been studying the galactic centre for many years. Among other things, the astronomers' attention is focused on a star called S2, which orbits the mass giant once every 16 years, approaching it to a distance of less than 20 billion kilometres. The precise orbital survey of S2 revealed a phenomenon described by Albert Einstein in his general theory of relativity: according to it, the elliptical orbit of a star does not remain stationary in space, but advances, as it were. In this way, several orbits of S2 result in the shape of a rosette, as illustrated in the image. The discovery was published in the spring of this year. A few months later, Reinhard Genzel received the Nobel Prize in Physics for his observations of the Milky Way black hole, together with Andrea Ghez and Roger Penrose.
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Dance around the heart of our Milky Way Computer visualization© ESO / L. Calçada