Illustration of the highest-resolution detections ever made from the surface of Earth

This artist’s impression shows the locations of multiple radio observatories across the planet, which participated in a pilot experiment conducted by the Event Horizon Telescope (EHT) Collaboration that obtained the highest-resolution observations from the ground. The test observations detected light from distant galaxies at a wavelength of 0.87 mm and were made with some of the observatories (in red) that are part of the EHT, a virtual Earth-sized telescope. One of these distant, point-like galaxies is represented on the top right, sending out radio signals all the way to Earth.

While non-ideal weather conditions hampered the observations at some of the sites, the team was able to observe multiple galaxies using multiple stations. Robust detections were made using different pairs of telescopes, indicated as glowing dots: the Atacama Large Millimeter/submillimeter Array (ALMA) and the Atacama Pathfinder EXperiment (APEX) in the Atacama Desert in Chile, ALMA and the IRAM 30-meter telescope in Spain, and ALMA and the Submillimeter Array in Hawaiʻi.

The EHT Collaboration is famous for connecting telescopes around the world, using a technique called very long baseline interferometry, to obtain images of supermassive black holes. Previous EHT observations were made at a wavelength of 1.3 mm. By observing a distant active galaxy at a lower wavelength, researchers were able to capture even higher resolution images without forming a bigger virtual telescope.