Astronomers have reconstructed 27 years of observations of a supermassive black hole jet in blazar 3C 345 using an AI model named Kine. The continuous video analysis reveals apparent speeds 10 to 13 times faster than light, challenging longstanding assumptions about how bright components move through plasma.
Researchers have transformed 116 separate observations of a distant black hole jet into the highest-definition continuous animation ever produced. The footage details the energetic behavior of 3C 345, a blazar located in the constellation Hercules, using archival data collected between 1995 and 2022. A blazar is a type of feeding supermassive black hole positioned at the center of a distant galaxy, shooting out relativistic jets charged with concentrated X-rays and gamma rays. As described in an Aug. 26 study in the journal Nature, scientists gathered the images of 3C 345 using decades of observations of a blazar at redshift 0.593 whose central supermassive black hole drives a relativistic jet inclined only about 3 to 6.8 degrees from our line of sight.
How Kine Reconstructed 27 Years of Observations
The underlying data came from the Very Long Baseline Array, a network of 10 radio antennas spread across the United States. Operating together as a virtual telescope thousands of kilometers wide, the array captured the 116 epochs through monitoring programs including BEAM-ME and MOJAVE at 15 gigahertz. Because the array uses only 10 antennas, its spatial sampling remains incomplete, requiring careful image reconstruction. Several study co-authors had previous experience boosting the resolution of distant black hole images while working at the Event Horizon Telescope Collaboration, the team behind the first image of a black hole.
To overcome those limitations, the research team employed an AI neural network named Kine. Traditional processing evaluates each observation independently, which can cause image-to-image flickering. Kine instead treats brightness and polarization as continuous functions of space and time, allowing a multilayer neural network to predict those quantities while a forward model matches the array’s actual radio measurements. The work appears in the peer-reviewed Nature paper Video reconstruction of variable VLBI observations with neural fields, led by Marianna Foschi, alongside co-authors B. Zhao, A. Fuentes, K. L. Bouman, J. L. Gómez, and A. Levis. The team has released code, observations, and supporting products.
Resolution Gains and Apparent Superluminal Speeds
Validation tests demonstrated that the continuous reconstruction achieved an average effective resolution of roughly 113 microarcseconds, about 4.2 times sharper than the nominal 475-microarcsecond beam. The total dynamic range reached about 500,000, which is approximately 140 times the conventional CLEAN result for this particular dataset. These factors are not universal promises for every radio observation, as the authors state that the gains depend on the amount, quality, and cadence of the data.
“The higher quality of our video reconstruction enabled a detailed measurement of the plasma velocity in the jet,” study first author Marianna Foschi, a postdoctoral researcher at Caltech, told Live Science in an email.
Marianna Foschi, postdoctoral researcher at Caltech, via Live Science
Analysis of the animation revealed that the jet’s bright components appeared to travel at 10 to 13 times the speed of light, while the surrounding bulk flow moved at roughly 9 to 12 times light speed in the same region. These are projected apparent velocities rather than local speeds through space, and they do not violate relativity. The near alignment makes the jet bright and creates the geometry behind its apparent faster-than-light motion.
Challenging the Standard Shock Model
The findings complicate established astrophysical frameworks. The general consensus attributes bright components to shock perturbations moving through the plasma, and as such they should have a higher velocity compared to the surrounding fluid.
“This is unexpected because the general consensus is that these bright components are shock perturbations moving through the plasma, and as such they should have a higher velocity compared to the surrounding fluid,” Foschi said. “Our work does not invalidate the shock model in general, but it puts it into question, at least in the case of this specific source.”
Marianna Foschi, Caltech, via Live Science
Foschi noted that the team is eager to apply Kine to other astronomical observations. We believe this method will drastically change the way jet dynamics is studied from observations,
she said, adding that the method enables a precise measurement of the projected velocity at any point in the jet.
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