The Event Horizon Telescope (EHT) Collaboration has made the highest resolution observations of the Universe ever achieved from the ground, according to a team of scientists.
Future observations using the same technique could lead to greater study and understanding of black holes, say the team behind the achievement.
The EHT is an array of telescopes stretching across the globe, most famous for its image of the supermassive black hole in galaxy M87 and the image of the supermassive black hole at the centre of the Milky Way.
Those images were achieved using a technique called ‘very long baseline interferometry’ (VLBI), which links up telescopes across the globe to form a single ‘Earth-sized’ virtual telescope.
Normally in astronomy,, better observations result from bigger telescopes, but since the EHT is already effectively the size of Earth, the team instead opted to observe in shorter wavelengths.
“With the EHT, we saw the first images of black holes using the 1.3-mm wavelength observations, but the bright ring we saw, formed by light bending in the black hole’s gravity, still looked blurry because we were at the absolute limits of how sharp we could make the images,” says study co-lead Alexander Raymond.
“At 0.87 mm, our images will be sharper and more detailed, which in turn will likely reveal new properties, both those that were previously predicted and maybe some that weren’t.”
How the 0.87 mm experiment was done
Rather than using the full EHT array for this experiment, the team used two smaller subarrays, including the ALMA and the Atacama Pathfinder EXperiment in Chile, the IRAM 30-meter telescope in Spain and the NOrthern Extended Millimeter Array (NOEMA) in France, as well as the Greenland Telescope and the Submillimeter Array in Hawaiʻi.
During the experiment they detected light from several distant galaxies and, while no images were captured, the team say they achieved observations with detail as fine as 19 microarcseconds, which is the highest-ever resolution achieved solely from the surface of Earth.
The team say that, using the full array, they would be able to see details as small as 13 microarcseconds, equivalent to being able to see a bottle cap on the Moon from Earth.
Looking back to those images of the black holes in M87 and the Milky Way, this new capability would amount to images with a resolution 50% higher than those previously captured.
And it could enable observations of black holes more distant and much smaller than those imaged so far.
“These VLBI signal detections at 0.87 mm are groundbreaking since they open a new observing window for the study of supermassive black holes”, says Thomas Krichbaum, co-author of the study from the Max Planck Institute for Radio Astronomy in Germany.
“In the future, the combination of the IRAM telescopes in Spain (IRAM-30m) and France (NOEMA) with ALMA and APEX will enable imaging of even smaller and fainter emission than has been possible thus far at two wavelengths, 1.3 mm and 0.87 mm, simultaneously.”