Composite image of the radio observatories that form the Event Horizon Telescope (EHT) network, used to image the Milky Way?™s central black hole, Sagittarius A*. From right to left are the Atacama Large Millimeter/submillimeter Array (ALMA), the James Clerk Maxwell Telescope (JCMT), the Submillimeter Array (SMA), the South Pole Telescope (SPT), the Large Millimeter Telescope (LMT), the Submillimeter Telescope (SMT), Atacama Pathfinder EXperiment (APEX) and the IRAM 30-meter telescope. The slightly transparent telescopes in the background represent the three telescopes added to the EHT network after 2018. From right to left are the UArizona ARO 12-meter Telescope, the Greenland Telescope and the NOrthern Extended Millimeter Array (NOEMA). The Event Horizon Telescope project is an international collaboration that was launched in 2009. The network of synchronised observatories combine as a single telescope with an aperture the size of Earth. They are used to observe sources of radio light associated with black holes.