The Technology Behind Our Images and Videos
To create high definition black hole images and movies, the next generation Event Horizon Telescope (ngEHT) will enhance every aspect of the current global array of radio telescopes that captured the first image of a supermassive black hole. Through a systematic approach and utilizing cutting edge technical advancements, the ngEHT will add brand new sites and dramatically improve the array’s capabilities. From new receivers that collect the faint radio waves from black holes, to the high-speed electronics that record these waves as digital signals, to the imaging algorithms that will create images faster than ever before, the ngEHT will be able to reveal details that are 100 times fainter than before.
Expanding the Telescope Array
The black hole M87* is in the center of a giant elliptical galaxy in the constellation Virgo, 55 million light years away. From Earth, the black hole looks about as large as an orange placed on the moon. It took an array of eight radio telescopes, spread across four continents, synchronized by atomic clocks, all observing at once to capture a photograph of M87. The original eight telescopes are: the Submillimeter Telescope, the Atacama Pathfinder EXperiment, the IRAM 30-m telescope, the James Clerk Maxwell Telescope, the Large Millimeter Telescope, the Submillimeter Array, the Atacama Large Millimeter/Sub-millimeter Array, and the South Pole Telescope.
Image credit: APEX, IRAM, G. Narayanan, J. McMahon, JCMT/JAC, S. Hostler, D. Harvey, ESO/C. Malin, and N. Conroy
This technique of uniting a diverse array of radio telescopes into a single large telescope is called very long baseline interferometry (VLBI). Using VLBI, the Event Horizon Telescope created a virtual telescope as large as the Earth. To capture a movie of a black hole, the next generation Event Horizon Telescope must join together even more telescopes.
Video Credit: Daniel Palumbo
Image Credit: Nick Conroy
The ngEHT will roughly double the number of antennas in its telescope array. Since the release of the first black hole picture, three sites have agreed to join the ngEHT: NOEMA in the French Alps, GLT in the Greenland ice sheets, and KP in the Quinlan Mountains of Arizona. These sites, like the eight original sites in the 2017 EHT array, house world-class radio telescopes. They lie far from civilization to limit radio noise and perch in dry places high above sea level to minimize the effects of water vapor in the Earth’s atmosphere.
Several additional sites, spread across North America, South America, and Africa, are also being considered as locations for additional 6–12 meter telescope dishes. The existing EHT array has a myriad of large and highly-sensitive sites, so adding several 6–10 meter dishes may be sufficient for obtaining high-quality data.
One day, the ngEHT may even be joined by space telescopes. Soaring above the Earth’s atmosphere, these telescopes are not limited by weather conditions. They can observe any time of the day and year, while greatly increasing the size of the ngEHT’s virtual telescope. A space telescope in low or medium Earth orbit or geostationary orbit would be a tremendous step forward for the vision of the ngEHT.
Image Credit: Freek Roelofs and Nick Conroy
Seeing in New Color
Light born in the accretion disk, the fiery cloud of gas surrounding a black hole, faces an arduous journey on its way to Earth. Most light waves don’t survive. Long radio waves get scattered in all directions by the hot gas that birthed them. Further, as light’s wavelength gets longer, the angular resolution of the resulting image decreases: any image made from long radio waves would be too blurry to see. Visible light gets absorbed by clouds of gas and dust in the interstellar medium, the large expanse of space between the stars. Ultraviolet light, X-rays, and gamma rays are blocked by our atmosphere. Only short radio waves around 1 millimeter long survive the odyssey and are useful for black hole imaging.
Video Credit: Smithsonian Astrophysical Observatory and Crazybridge Studios
The Event Horizon Telescope observed black holes using the 1.3-millimeter wavelength. In effect, the EHT took a black hole picture using only one color in the radio spectrum. The ngEHT will take pictures and videos with a second color: 0.87-millimeter-long radio waves. This two-color picture will require massive upgrades to every telescope in the array. The reward—clearer images, better-rendered movies, a greater understanding of a black hole’s magnetic field—will be worth it.
Simulation Credit: CK Chan
Dual-band receivers capable of capturing light at both 1.3 millimeters and 0.87 millimeters must be developed, deployed, and installed at telescopes across the ngEHT array. These receivers will dramatically increase the amount of data captured. With more data captured, there must be more data transferred and recorded. By developing new back end technology with an increased bandwidth (data transfer rate), the ngEHT will double the EHT’s recording rate of 64 gigabits per second. The EHT’s recording rate may one day be quadrupled, allowing a recording rate of a whopping 256 gigabits per second.
Image Credit: First M87 Event Horizon Telescope Results. II. Array and Instrumentation
Streamlining Data Transport and Processing
Image Credit: Lindy Blackburn
Black hole images require immense quantities of data. The famous 2019 image required 5 petabytes of data. That’s equivalent to 40,000 lifetime’s worth of selfies. Scientists must consolidate this data in one place for processing. It turns out the fastest way to transport petabytes of data, captured at 8 sites across the globe, is to carry it in hard drives by hand. At its peak, this manual method of transporting data by plane was actually the fastest data transmission in astronomy history.
Still, this method comes with risks: data can be damaged in shipment, experimental errors can go unseen until the processing stage, and delivery from the South Pole Telescope can take up to six months. The next generation Event Horizon Telescope is developing an even faster method of data transfer. Space laser communication shows the potential to move many terabits per second. With this technology, the ngEHT team may again break the record for fastest data transmission in astronomy history.
Image Credit: Joseph Farah
Improving Imaging and Analysis Techniques
The Technology Behind Our Images and Videos
To create high definition black hole images and movies, the next generation Event Horizon Telescope (ngEHT) will enhance every aspect of the current global array of radio telescopes that captured the first image of a supermassive black hole. Through a systematic approach and utilizing cutting edge technical advancements, the ngEHT will add brand new sites and dramatically improve the array’s capabilities. From new receivers that collect the faint radio waves from black holes, to the high-speed electronics that record these waves as digital signals, to the imaging algorithms that will create images faster than ever before, the ngEHT will be able to reveal details that are 100 times fainter than before.
Expanding the Telescope Array
The black hole M87* is in the center of a giant elliptical galaxy in the constellation Virgo, 55 million light years away. From Earth, the black hole looks about as large as an orange placed on the moon. It took an array of eight radio telescopes, spread across four continents, synchronized by atomic clocks, all observing at once to capture a photograph of M87. The original eight telescopes are: the Submillimeter Telescope, the Atacama Pathfinder EXperiment, the IRAM 30-m telescope, the James Clerk Maxwell Telescope, the Large Millimeter Telescope, the Submillimeter Array, the Atacama Large Millimeter/Sub-millimeter Array, and the South Pole Telescope.
Image credit: APEX, IRAM, G. Narayanan, J. McMahon, JCMT/JAC, S. Hostler, D. Harvey, ESO/C. Malin, and N. Conroy
This technique of uniting a diverse array of radio telescopes into a single large telescope is called very long baseline interferometry (VLBI). Using VLBI, the Event Horizon Telescope created a virtual telescope as large as the Earth. To capture a movie of a black hole, the next generation Event Horizon Telescope must join together even more telescopes.
Video Credit: Daniel Palumbo
Image Credit: Ming-Tang Chen, IRAM & DiVertiCimes, Arash Roshanineshat, and Nick Conroy
The ngEHT will roughly double the number of antennas in its telescope array. Since the release of the first black hole picture, three sites have agreed to join the ngEHT: NOEMA in the French Alps, GLT in the Greenland ice sheets, and KP in the Quinlan Mountains of Arizona. These sites, like the eight original sites in the 2017 EHT array, house world-class radio telescopes. They lie far from civilization to limit radio noise and perch in dry places high above sea level to minimize the effects of water vapor in the Earth’s atmosphere.
Several additional sites, spread across North America, South America, and Africa, are also being considered as locations for additional 6–12 meter telescope dishes. The existing EHT array has a myriad of large and highly-sensitive sites, so adding several 6–10 meter dishes may be sufficient for obtaining high-quality data.
One day, the ngEHT may even be joined by space telescopes. Soaring above the Earth’s atmosphere, these telescopes are not limited by weather conditions. They can observe any time of the day and year, while greatly increasing the size of the ngEHT’s virtual telescope. A space telescope in low or medium Earth orbit or geostationary orbit would be a tremendous step forward for the vision of the ngEHT.
Other potential sites can be found here. Image Credit: Alex Raymond
Seeing in New Color
Light born in the accretion disk, the fiery cloud of gas surrounding a black hole, faces an arduous journey on its way to Earth. Most light waves don’t survive. Long radio waves get scattered in all directions by the hot gas that birthed them. Further, as light’s wavelength gets longer, the angular resolution of the resulting image decreases: any image made from long radio waves would be too blurry to see. Visible light gets absorbed by clouds of gas and dust in the interstellar medium, the large expanse of space between the stars. Ultraviolet light, X-rays, and gamma rays are blocked by our atmosphere. Only short radio waves around 1 millimeter long survive the odyssey and are useful for black hole imaging.
Video Credit: Smithsonian Astrophysical Observatory and Crazybridge Studios
The Event Horizon Telescope observed black holes using the 1.3-millimeter wavelength. In effect, the EHT took a black hole picture using only one color in the radio spectrum. The ngEHT will take pictures and videos with a second color: 0.87-millimeter-long radio waves. This two-color picture will require massive upgrades to every telescope in the array. The reward—clearer images, better-rendered movies, a greater understanding of a black hole’s magnetic field—will be worth it.
Simulation Credit: CK Chan
Dual-band receivers capable of capturing light at both 1.3 millimeters and 0.87 millimeters must be developed, deployed, and installed at telescopes across the ngEHT array. These receivers will dramatically increase the amount of data captured. With more data captured, there must be more data transferred and recorded. By developing new back end technology with an increased bandwidth (data transfer rate), the ngEHT will double the EHT’s recording rate of 64 gigabits per second. The EHT’s recording rate may one day be quadrupled, allowing a recording rate of a whopping 256 gigabits per second.
Image Credit: First M87 Event Horizon Telescope Results. II. Array and Instrumentation
Streamlining Data Transport and Processing
Image Credit: Lindy Blackburn
Black hole images require immense quantities of data. The famous 2019 image required 5 petabytes of data. That’s equivalent to 40,000 lifetimes' worth of selfies. Scientists must consolidate this data in one place for processing. It turns out the fastest way to transport petabytes of data, captured at 8 sites across the globe, is to carry it in hard drives by hand. At its peak, this manual method of transporting data by plane was actually the fastest data transmission in astronomy history.
Still, this method comes with risks: data can be damaged in shipment, experimental errors can go unseen until the processing stage, and delivery from the South Pole Telescope can take up to six months. The next generation Event Horizon Telescope is developing an even faster method of data transfer. Space laser communication shows the potential to move many terabits per second. With this technology, the ngEHT team may again break the record for fastest data transmission in astronomy history.
Image Credit: Joseph Farah
Improving Imaging and Analysis Techniques
The Event Horizon Telescope used revolutionary imaging techniques to produce black hole images. If the next generation Event Horizon Telescope is to succeed, it must do the same. The ngEHT must establish new techniques to generate movies using a virtual earth-sized telescope, created using many telescopes spread across the globe. It must develop custom methods to calibrate data and correct for fringe patterns, which can tarnish an image. Our imaging techniques must accommodate the addition of new wavelengths to the data, they must overcome the scattering of light waves on their way from a black hole to Earth, and they must account for the impact of the Earth’s atmosphere. Like the EHT before it, the ngEHT will be at the forefront of astronomical imaging.
Image Credit: ESO and M. Kornmesser
Apart from the imaging techniques, the ngEHT will also improve on the analysis techniques used to extract the relevant science from the data and images. The increased baseline coverage will give access to information that we cannot recover with the current EHT, such as the presence of faint jet or disk features and the variability of the image over time. These troves of new information warrant the development of new analysis techniques. By optimizing these techniques, we aim to maximally increase our precision in measuring quantities like the black hole mass and spin, while expanding our understanding of the plasma and magnetic field behavior.