Dynamics and geometry of the inner sub-parsec-scale jet in 3C 279 observed with the Event Horizon Telescope
Event Horizon Telescope observations of the blazar 3C 279 reveal an intrinsically orthogonal, compact core with ultra-relativistic speeds and low brightness temperatures, indicating that the inner jet bends sharply toward the observer on sub-parsec scales, though current data remains insufficient to pinpoint the specific physical mechanism driving this geometry.
Original paper licensed under CC BY 4.0 (http://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
Imagine the universe as a giant, cosmic ocean, and scattered throughout it are lighthouses that don't just shine light, but shoot out powerful, super-fast beams of energy. These are called "jets," and they are launched by supermassive black holes—the ultimate cosmic vacuum cleaners sitting at the centers of galaxies. For decades, astronomers have been trying to figure out exactly how these black holes turn on their jets, how they keep them straight, and why they sometimes wiggle or bend. It's like trying to understand how a garden hose sprays water when the nozzle is attached to a spinning, invisible motor. The question matters because these jets carry huge amounts of energy across the universe, shaping how galaxies grow and evolve. To see the very beginning of these jets, right where they leave the black hole, we need a telescope so powerful it can see a coin on the Moon from Earth. That's what the Event Horizon Telescope (EHT) is: a global team of radio dishes working together to create a virtual telescope the size of our planet.
Now, let's zoom in on a famous cosmic lighthouse called 3C 279. In this new study, the EHT team took a super-sharp look at the very base of 3C 279's jet in 2021. What they found was a bit of a surprise. Instead of a straight beam shooting out like a laser, the inner part of the jet looks like a bent, hook-shaped noodle. It's almost perpendicular to the direction the jet travels further out, as if the jet suddenly decided to do a sharp turn right at the source. The team used three different computer "imaging" methods to reconstruct the picture, and all of them agreed on this weird, bent shape. It's not a glitch; it's real.
The scientists measured how fast the bright knots of energy inside this bent jet are moving. They found some parts are zooming along at speeds that look like they are 10 times faster than light (a trick of perspective called "apparent speed" because the jet is pointing almost directly at us). This tells us the jet is moving incredibly fast, with a "bulk Lorentz factor" (a fancy way of saying how fast it is relative to the speed of light) of at least 10.3. Because the jet is moving so fast and pointing so straight at Earth, the light gets super-bright, like a headlight shining right in your eyes.
But here is the big mystery: why is the jet bent? The paper suggests a few possibilities. Maybe the jet is crashing into gas around the black hole, like a hose hitting a wall. Maybe it's wobbling because of magnetic forces snapping and reconnecting near the black hole. Or, perhaps the black hole itself is part of a pair, and the dance between two black holes is making the jet precess, or wobble, like a spinning top. The authors are careful to say they haven't proven which one it is yet. They explicitly rule out the idea that this bent shape is just a mistake in their pictures or a temporary glitch. They also note that while some people think a binary black hole system might be the cause, there isn't enough evidence yet to say that for sure.
The team also looked at how the jet has changed over the years. By comparing their 2021 photos with older ones from 2011 and 2017, they saw that the jet's shape and direction have shifted. It's like watching a time-lapse video of a river changing its course. This suggests the jet is dynamic and alive, constantly rearranging itself on scales of just a few light-days. The paper concludes that while we have a great new picture of this bent, super-fast jet, we need to keep watching it over many more years to finally solve the puzzle of what is bending it. For now, we know the jet is a wild, fast, and twisting thing, and the EHT has given us our best view yet of its chaotic dance floor.
Drowning in papers in your field?
Get daily digests of the most novel papers matching your research keywords — with technical summaries, in your language.