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The Event Horizon telescope has obtained unprecedented high-resolution observations from Earth using a frequency of 345 GHz, providing more detailed and colorful images of black holes. This advance
The Event Horizon telescope has obtained unprecedented high-resolution observations from Earth using a frequency of 345 GHz, providing more detailed and colorful images of black holes. This advance in astrophysics uses very-long-baseline interferometry to link multiple radio antennas around the world, improving our understanding of the phenomena surrounding black holes and laying the groundwork for future high-precision visualizations, and possibly real-world images, of these cosmic entities.
The Event Horizon Telescope (EHT) collaboration has made test observations, detecting light at a frequency of around 345 GHz from the centers of distant galaxies, achieving the highest resolution ever achieved from the Earth’s surface.
When combined with existing images of the lower-frequency 230 GHz supermassive black holes at the heart of M87 and Sgr A, these new results will not only make images of the black holes 50% sharper, but will also produce multi-color images of the region just beyond the edge of these space monsters.
The new discoveries, led by scientists from the Center for Astrophysics at Harvard & Smithsonian (CfA), which includes the Smithsonian Astrophysical Observatory (SAO), were released today. Astronomy Journal.
“We saw the first images of black holes detecting radio waves at 230 GHz with the EHT, but the bright ring we saw, created by the bending of light by the black hole’s gravity, still appeared blurry because we were at the absolute limits of sharpness. We can now build up an image,” said co-author Alexander Raymond, a former postdoctoral researcher at CfA and now at NASA’s Jet Propulsion Laboratory (NASA-JPL). “At 345 GHz, our images will be sharper and more detailed, and this will likely reveal new features, both previously predicted and some not predicted.”
The EHT uses a technique called very-long-baseline interferometry (VLBI) to link several radio antennas around the world, creating a virtual telescope the size of the Earth. To get higher-resolution images, astronomers have two options: increase the distance between the radio antennas or observe at a higher frequency. Since the EHT is already the size of our planet, increasing the resolution of ground-based observations required expanding the frequency range, and that’s exactly what the EHT collaboration is doing now.
“To understand why this is a breakthrough, think of the extra burst of detail you get when you go from black-and-white photos to color,” said astrophysicist Shepherd “Shep” Doleman, co-founder of the CfA and SAO and director of the EHT. “This new ‘color view’ allows us to separate the effects of Einstein’s gravity from the hot gas and magnetic fields that feed black holes and propel powerful jets that travel galactic distances.”
A prism separates white light into rainbow colors because different wavelengths of light pass through the glass at different speeds. But gravity bends all light in a similar way, so Einstein predicts that the rings seen by the EHT should be the same size at both 230 GHz and 345 GHz, while black holes orbiting hot gas will appear different at those two frequencies.
This is the first time that VLBI has been used successfully at 345 GHz. Although the ability to observe the night sky at 345 GHz with individual telescopes has existed in the past, using VLBI at this frequency has long presented challenges that have taken time and technological advances to overcome. Water vapor in the atmosphere absorbs waves at 345 GHz much more than at 230 GHz, weakening the signals from black holes at higher frequencies. The key was to increase the sensitivity of the EHT, which the researchers did by increasing the bandwidth of the instruments and waiting for good weather conditions across the board.
The new experiment used two smaller EHT sub-arrays — the Atacama Large Millimeter/submillimeter Array (ALMA) and the Atacama Pathfinder Experiment (APEX) in Chile, the 30-meter IRAM telescope in Spain and the Northern Extended Millimeter Array (NOEMA) in France, the Submillimeter Array (SMA) on Maunakea in Hawaii, and the Greenland Telescope — to make measurements with a resolution down to 19 microcubic seconds.
“The most powerful observatories on Earth are at high altitudes, where atmospheric transparency and stability are optimal, but weather can be more dramatic,” said Nimesh Patel, an astrophysicist at CfA and SAO and project engineer at SMA. The new observations required driving across icy roads on Maunakea to open up the massif in stable weather conditions after a snowstorm, and staying there for several minutes. “We are now starting to overcome fundamental sensitivity issues, such as weather, with broadband systems that process and capture a wider range of radio frequency bands. As the new findings demonstrate, it is time to move to 345 GHz.”
This achievement is another step toward creating high-quality movies of event horizon environments around black holes, which will also be based on an upgrade of the existing global array. The planned Next Generation EHT (ngEHT) project will add new antennas to the EHT at optimized geographic locations and upgrade all of the existing stations to operate simultaneously on multiple frequencies between 100 GHz and 345 GHz. As a result of these and other upgrades, the global array is expected to increase the amount of sharp, clear data the EHT has for imaging by a factor of 10, allowing scientists to not only create more detailed and precise images, but also to shoot movies with very brutal roles. space monsters
“The successful observation of the EHT at 345 GHz is a significant scientific milestone,” said Lisa Kewley, director of the CfA and SAO. “By pushing the boundaries of resolution, we are achieving the unprecedented clarity in imaging black holes that we were originally promised, and setting new and higher standards for ground-based astrophysics capabilities.”
Source: Port Altele
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