Scientists achieve highest resolution black hole image ever from Earth

The Event Horizon Telescope (EHT) collaboration has set a new standard for Earth-based observations.

Interestingly, the EHT team was able to undertake the “highest resolution” observation from Earth’s surface of a black hole hiding in the heart of the faraway galaxy.

The EHT is a global network of telescopes, working together to create a virtual Earth-sized instrument.

In this test observation, EHT detected light from distant galaxies at a frequency of 345 GHz — corresponding to a wavelength of 0.87 mm.

This feat paves the way for more shaper images of the cosmic monsters, revealing new properties and insights into their behavior. In fact, the EHT expects 50% sharper black hole images from Earth in the future.

“With the EHT, we saw the first images of black holes by detecting radio waves at 230 GHz, 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,” explained Alexander Raymond, paper co-lead.

Raymond added: “At 345 GHz, 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.”

High-frequency image

EHT uses a very-long-baseline interferometry (VLBI) technique to create a virtual Earth-sized telescope.

EHT is well-known for taking the first supermassive black hole image of M87* —situated in the center of the M87 galaxy — in 2019. In 2022, EHT took a photograph of Milky Way’s black hole Sgr A*.

Remarkably, this was the first highest frequency observation at 345 GHz done using the VLBI technique.

While single telescopes could observe the night sky at 345 GHz, the VLBI technique presented significant challenges at this frequency. For instance, atmospheric water vapor acts as a major obstacle for black hole observations at 345 GHz. It absorbs these signals more strongly than those at 230 GHz.

For this high-resolution observation, the team improved the sensitivity of the EHT to use VLBI at 345 GHz. This was made possible by a combination of technological advancements, including increased bandwidth. Moreover, strategic planning played a key role, such as waiting for optimal weather conditions at all observing sites.

Sharper movies in the future

The EHT experiment utilized a combination of powerful telescopes, including the Atacama Large Millimeter/submillimeter Array (ALMA), the Atacama Pathfinder EXperiment (APEX), the IRAM, the NOrthern Extended Millimeter Array (NOEMA), Submillimeter Array (SMA), and the Greenland Telescope.

The power of these advanced telescopes was combined to achieve a remarkable resolution of 19 microarcseconds.

“The most powerful observing locations on Earth exist at high altitudes, where atmospheric transparency and stability is optimal but weather can be more dramatic,” said Nimesh Patel, an astrophysicist at the Center for Astrophysics | Harvard & Smithsonian (CfA).

“Now, with high-bandwidth systems that process and capture wider swaths of the radio spectrum, we are starting to overcome basic problems in sensitivity, like weather. The time is right, as the new detections prove, to advance to 345 GHz,” Patel added.

As per the press release , EHT’s latest feat brings experts closer to creating high-fidelity movies of black holes. They will be able to create movies of the event horizon region — the point of no return for matter falling into a black hole.

The future of black hole imaging is bright, as the ngEHT project promises to significantly enhance the EHT network. The ngEHT is expected to add new antennas and upgrade existing ones.

The findings have been published in the Astronomical Journal .