5 Years After the First Black Hole Image, Physicists Unveil A New Experiment To Map Space-Time
The first video of a churning black hole would be revolutionary.
Five years ago, on April 10, 2019, the Event Horizon Telescope — a matrix of radio observatories situated around the world that turn the Earth into one giant radio telescope — captured something incredible: The first-ever image of the hollow depths of a black hole. The clear, almost simplistic image provides the strongest evidence that black holes actually exist and that they match what theoretical physicists predicted. Now, astronomers are attempting something even more surreal: The first-ever movie of a black hole — and it might look like a flipbook.
More than 400 scientists are now collaborating on the next generation of the Event Horizon Telescope (EHT). They are taking snapshots of the supermassive black hole at the center of galaxy Messier 87 (M87) — which is the black hole they took that original image of five years ago — to see how it changes over time. EHT has set a goal of making the video by 2026. The movie will probably be a synopsis of scenes taken over two months.
The appearance of black hole M87* changes from one image to the next, taken a year apart. EHT published the April 11, 2017 observation two years later in 2019. EHT published the 2018 observation (right) in January 2024. In one Earth year, the brighest peak of the ring shifted by about 30 degrees, according to EHT.
If EHT succeeds at its current negotiations for funding and booking global telescope access during the optimal observation months of March and April, the researchers working on the project could turn the images taken every third day into a moving picture. “We have half a year left to convince everyone that we can do this,” Remo Tilanus, research professor at the University of Arizona and EHT operations manager, tells Inverse.
Vlogging a black hole
EHT works by turning the Earth into a giant radio telescope. EHT facilities around the world act like parts of a lens. When our planet turns on its axis, the telescopes shift their position relative to the black hole, acting as different parts of that lens.
Scientists have once again set their eyes on M87*. The black hole was a Goldilocks candidate for an image, Paulina Lira, an astrophysics professor at the University of Chile who was not involved with the work, tells Inverse. She studies the most powerful supermassive black holes, which she says would have likely been too bright to allow the central shadow to appear.
M87* is also more robust than smaller, tamer supermassive black holes, so it will be ideal for a video. Material orbits the black hole on the order of days or weeks. That’s a slow enough time to capture a still image of it but also fast enough for scientists to see changes over 60 days.
That’s a much longer timescale than the other major EHT target, the Milky Way’s supermassive black hole called Sagittarius A*. Our neighborhood monster is much smaller, with much less stuff going around it that takes just minutes to orbit.
A video of a black hole will require significant upgrades both to the EHT’s technology and the number of arrays involved. Instead of the handful of days required to take a still image, a video of a black hole will take about 60 days, which is far more challenging, says Tilanus. In addition to booking the right arrangements at the observatories, a video requires EHT to observe in more wavelengths, which requires improvements to the telescopes. Taking the video will also get easier as more observatories join EHT. The larger the array, and the more radio wavelengths that can be collected, the higher the quality of the black hole images.
“We have completed an initial design of the [next generation] EHT upgrades and are now sourcing the funds required to build the array. We hope to obtain movies from the upgraded array in the next several years,” Lindy Blackburn, an astronomer and EHT data scientist at the Center for Astrophysics | Harvard and Smithsonian, tells Inverse via email.
The updates will allow EHT to reconstruct models of the black hole’s dynamics from existing data, and the new telescopes over the next several years will be key to making “high fidelity movies that show the inflow and outflow dynamics near the boundary of a black hole,” Blackburn says.
A video is worth a thousand images
The University of Chile’s Lira says the original black hole image far surpassed her expectations. Its impact on scientists, and popularity amongst the public, she says, came from its simplicity: a clear, non-pixelated, shadow of a black hole against a bright ring. Memes, like her personal favorite of the donut-shaped black hole held by Homer Simpson, highlight the universal appeal of the visual.
The video would catapult black hole work. In the video, astronomers say they might see bright spots, in the ring of super-hot plasma, changing as they orbit the black hole M87*. Astrophysicists could better understand M87*’s jet, which stretches out 5,000 light-years long, yet originates from a black hole smaller than the size of the Solar System.
Tilanus says a video would show how a black hole ingests and ejects matter, how that in turn might be creating the magnetic field lines that funnel matter into a jet, and how that phenomenon affects star formation in the galaxy or halts them altogether. On a more macro-level, the video could reveal what the first black holes were like, and how the supermassive ones that lurk in most if not all the universe’s galaxies come to be.
The video could give clues about a major cosmic evolution debate. It's a “chicken or the egg” question: Did black holes emerge first from the gas and dust of the early universe, and did galaxies grow around them? Or, did galaxies form first and then create these black hole behemoths at their hearts?
In addition, a video could also help theoretical physicists learn by what degree time slows down if an object were to fall into a black hole.
Chi-kwan Chan, an associate research professor at the University of Arizona and EHT data scientist, tells Inverse that there are already predictions for a black hole’s time dilation, given Albert Einstein’s theory of general relativity. “But, unless you can do an experiment, it’s not really confirmed. It’s not really science. One of the biggest contributions for the EHT [work] that’s coming up is really to confirm these theoretical predictions,” Chan says.
A diagram of a rapidly spinning supermassive black hole and its accretion disk.
Einstein’s theory of general relativity says that time is a dimension in the universe: Time can change; it is not absolute. That’s in contrast to the Newtonian view of physics, where time and space are in the background. Einstein predicted that extreme mass could modify time.
Space-time can be thought of as an elastic surface, which will stretch if a weight is on it. Likewise, a massive object like a black hole will stretch space-time, and thus slow down time.
How fast material moves in a black hole depends on the curvature of space-time, says Chan. The more curved, the more distorted it will be. Only a video could give insight into this phenomenon.
A video would allow theoretical physicists to map the time dilation. An image of a black hole, however spectacular, lacks time-dependent information.
Time dilation data in a movie would be a major win for theoretical physicists because black holes are complicated systems, and most of the current work on black holes is done on supercomputers and simulations.
If humanity achieves this incredible feat, physicists will take a major step toward understanding the chaotic environment of a black hole. “The first time I heard about the project and its goals, it sounded fantastically challenging bordering on unachievable,” says Blackburn. “That is also a very fun place to be.”
