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18 JULY-AUGUST 2022 ASTRO PUBLISHING Extended Millimeter Array (NOEMA) in France — as well as a supercom- puter to combine EHT data hosted by the Max Planck Institute for Radio Astronomy in Germany. Moreover, Europe contributed with funding to the EHT consortium proj- ect through grants by the European Research Council and by the Max Planck Society in Germany. “It is very exciting for ESO to have been playing such an important role in unravelling the mysteries of black holes, and of Sgr A* in particular, over so many years,” commented ESO Director General Xavier Bar- cons. “ESO not only contributed to the EHT observations through the ALMA and APEX facilities but also enabled, with its other observato- ries in Chile, some of the previous breakthrough observations of the Galactic centre.” The EHT achievement follows the collaboration’s 2019 release of the first image of a black hole, called M87*, at the centre of the more dis- tant Messier 87 galaxy. The two black holes look remarkably similar, even though our galaxy’s black hole is more than a thou- sand times smaller and less massive than M87*. “We have two completely different types of galaxies and two very different black hole masses, but close to the edge of these black holes they look amazingly similar,” says Sera Markoff, Co-Chair of the EHT Science Council and a professor of theoretical astrophysics at the University of Amsterdam, the Nether- lands. “This tells us that General Relativity governs these objects up close, and any differences we see further away must be due to differ- ences in the material that surrounds S ize comparison of the two black holes imaged by the Event Horizon Telescope (EHT) Collabo- ration: M87*, at the heart of the galaxy Messier 87, and Sagittarius A* (Sgr A*), at the centre of the Milky Way. The image shows the scale of Sgr A* in comparison with both M87* and other ele- ments of the Solar System such as the orbits of Pluto and Mercury. Also displayed is the Sun’s di- ameter and the current location of the Voyager 1 space probe, the furthest spacecraft from Earth. M87*, which lies 55 million light-years away, is one of the largest black holes known. While Sgr A*, 27,000 light-years away, has a mass roughly four million times the Sun’s mass, M87* is more than 1000 times more massive. Because of their relative distances from Earth, both black holes ap- pear the same size in the sky. [EHT collaboration (acknowledgment: Lia Medeiros, xkcd)] the black holes.” This achievement was considerably more difficult than for M87*, even though Sgr A* is much closer to us. EHT scientist Chi- kwan (‘CK’) Chan, from Steward Observatory and Department of As- tronomy and the Data Science Insti- tute of the University of Arizona, USA, explains: “The gas in the vicin- ity of the black holes moves at the same speed — nearly as fast as light