How did the Event Horizon Telescope image Sagittarius A*?

The Event Horizon Telescope (EHT) imaged Sagittarius A* by capturing the light from hot, bright gas surrounding the black hole that is bent by the object's intense gravity, revealing the black hole's shadow against that gas.1

To achieve the necessary resolution to image such a compact source, the EHT utilizes very long baseline interferometry (VLBI). This technique links radio telescopes across the globe to function as a single, Earth-sized virtual telescope. Because physical connections between such distant antennas are impractical, the system records signals at each site using highly stable hydrogen maser frequency standards for precise synchronization. These recorded data are later combined at a central location to synthesize the final image.12