Have you ever wondered what happens when the fabric of the universe itself gets twisted like taffy? What if space and time—the invisible stage on which everything exists—could be dragged around by a spinning cosmic monster?
Welcome to FreeAstroScience.com, where we break down mind-bending discoveries into ideas you can hold onto. Today, we're taking you on a journey to a galaxy 400 million light-years away. There, a star met its violent end. And in its death, it handed us proof of something Einstein's colleagues predicted over a century ago.
Grab a cup of coffee. This one's going to change how you see the cosmos.
What Exactly Did Scientists Just Catch on Camera?
In early 2024, telescopes around the world locked onto something extraordinary. A star was being ripped apart by a supermassive black hole—an event astronomers call a tidal disruption event (TDE). But this wasn't just another cosmic meal.
The dying star's remains began to wobble. Not randomly. Rhythmically. Every 19.6 days, like clockwork, the X-ray and radio signals pulsed in sync .
This wasn't supposed to happen. Or rather—it was supposed to happen, according to theory. But we'd never actually seen it before.
The event, named AT2020afhd, gave us the first direct evidence that a spinning black hole can drag the very fabric of space-time around with it. We call this Lense-Thirring precession, or more poetically: frame dragging .
The Einstein Connection: What Is Frame Dragging?
Let's rewind to 1915. Albert Einstein published his general theory of relativity. He told us that massive objects don't just sit in space—they warp it. Think of a bowling ball on a trampoline. The ball creates a dip, and anything rolling nearby curves toward it.
But what if that bowling ball was spinning? Three years later, in 1918, physicists Josef Lense and Hans Thirring took Einstein's math further. They calculated that a rotating mass would drag space-time along with it—like honey swirling around a spinning spoon .
For over a century, we believed this was true. The math checked out. But proving it? That's another story entirely.
Here's the aha moment: we finally caught the universe doing what Einstein said it would.
How a Star's Death Revealed the Truth
The Anatomy of a Tidal Disruption Event
Imagine a star wandering too close to a supermassive black hole. The gravitational pull on the near side of the star is vastly stronger than on the far side. This difference—called tidal force—stretches the star into a long spaghetti-like strand .
(Yes, physicists really call this spaghettification. Science has a sense of humor.)
The stellar debris spirals inward, forming a flat, spinning disk of superheated material called an accretion disk. Some of this matter gets swallowed. Some gets blasted out in powerful twin jets traveling near the speed of light .
Both the disk and the jets glow brightly across the electromagnetic spectrum—X-rays, visible light, radio waves. And that's how we spotted AT2020afhd.
The Wobble That Changed Everything
When the team led by Yanan Wang at the Chinese Academy of Sciences analyzed the data, they noticed something strange. The X-ray brightness wasn't steady. It rose and fell dramatically—by more than a factor of 10—every 19.6 days .
Even more surprising: the radio emissions wobbled too. And they did it in sync with the X-rays .
| Parameter | Value |
|---|---|
| Quasi-periodic variation | 19.6 ± 1.5 days |
| X-ray amplitude change | >10× (peak to dip) |
| Black hole mass | ~5 million solar masses |
| Distance from Earth | ~400 million light-years |
| Black hole spin | 0.11–0.35 (low spin) |
This synchronization was the smoking gun. It meant the disk and the jet were precessing together—wobbling like a tilted spinning top. And the only thing that could cause this? The black hole dragging space-time itself .
Why This Discovery Matters So Much
A 107-Year-Old Prediction Comes True
We've had hints of frame dragging before. NASA's Gravity Probe B mission detected it around Earth in 2011. But Earth is a lightweight compared to a supermassive black hole. The effect was minuscule—about 37 milliarcseconds per year.
Around AT2020afhd's black hole, the effect is violent. Strong enough to make an entire accretion disk—and its jet—oscillate every three weeks .
As Cosimo Inserra from Cardiff University put it: "This is a real gift for physicists" . We're not just confirming old predictions. We're watching them play out in real time, with details we can study.
A New Window Into Black Hole Physics
Here's what excites scientists even more: we now have a tool.
By measuring how fast a disk precesses, we can estimate the black hole's spin. In this case, the spin parameter came out between 0.11 and 0.35—relatively slow for a black hole . That's valuable information.
We can also study how black holes "eat." The material in the disk doesn't flow smoothly. It spirals, heats up, and releases energy in complex patterns. Understanding these patterns helps us learn how galaxies grow and evolve.
The Technical Side: How Did They Prove It?
If you're curious about the nitty-gritty, here's a simplified breakdown.
Instruments and Observations
The team used an impressive array of tools:
- Neil Gehrels Swift Observatory (NASA) – Captured X-ray data
- NICER (on the ISS) – High-cadence X-ray monitoring
- Karl G. Jansky Very Large Array (VLA) – Radio observations
- Australia Telescope Compact Array (ATCA) – More radio data
- Very Long Baseline Array (VLBA) – Ultra-precise radio imaging
- e-MERLIN (UK) – Additional radio coverage
They monitored AT2020afhd from January 2024 through late November 2024—almost a full year of dedicated observations .
The Math Behind the Wobble
The precession period depends on several factors:
Where:
- Tprec = precession period
- MBH = black hole mass
- a* = spin parameter
- Rdisk = disk size
By plugging in the observed period of 19.6 days and the estimated black hole mass (~5 million solar masses), the team constrained the spin to a narrow range .
The viewing angle also mattered. The observer's line of sight relative to the black hole's spin axis was about 38°, while the disk tilted by roughly 14.5° . This geometry allowed the precession to produce visible brightness changes as the disk alternately showed more or less of its luminous surface.
What Makes AT2020afhd Different?
Plenty of TDEs have been observed before. So why is this one special?
Most TDEs show steady radio signals. AT2020afhd didn't. Its short-term radio variability couldn't be explained by standard energy release from accretion .
Previous observations had detected disk precession or jet precession—but never both at the same time. AT2020afhd showed them moving together, in lockstep . That's the coprecession in the paper's title. It's the first clear case we've ever found.
The Bigger Picture: Spinning Black Holes and the Cosmos
Black holes spin because the stars and gas that formed them were spinning. Angular momentum doesn't just disappear. It gets concentrated into these dark gravitational wells.
But we've never had a great way to measure black hole spin from a distance. X-ray spectroscopy can give hints. Gravitational wave observations from merging black holes provide data. But those methods have limitations.
Disk-jet coprecession from TDEs offers a new approach. If we can find more events like AT2020afhd, we can build a census of black hole spins across the universe.
Why does spin matter? Because it affects everything:
- How efficiently black holes power jets
- How accretion disks behave
- How merging black holes emit gravitational waves
- How galaxies co-evolve with their central black holes
What Comes Next?
The discovery opens exciting doors.
The team suggests using X-ray variability as a trigger for high-cadence radio follow-ups . When a TDE starts showing periodic X-ray dips, we should point radio telescopes at it immediately. This strategy could expand our sample of frame-dragging events.
New missions will help too. The Einstein Probe (launched in 2024) is designed to catch transient X-ray events. Future radio arrays will provide even sharper views.
We're entering an era where relativity isn't just equations in textbooks. It's something we can observe, measure, and test with real data from real events happening across cosmic distances.
Why You Should Care
You might be thinking: Okay, cool physics. But what does this mean for me?
Fair question. Here's our answer.
Every time we confirm a prediction from fundamental physics, we strengthen our understanding of reality. General relativity doesn't just describe black holes. It makes GPS satellites work. It explains how time passes differently at different altitudes. It shapes our entire technological civilization.
When we see frame dragging in action, we're watching the universe validate the deepest theories we have. That's not just intellectually satisfying—it's reassuring. It tells us that human reason, applied carefully, can truly grasp the workings of nature.
And there's something poetic about it. A star that died 400 million years ago, torn apart by an ancient gravitational monster, sent us a message across unimaginable distances. That message confirmed an idea two Austrian physicists worked out with pencil and paper in 1918.
We're connected to the cosmos more than we realize.
Wrapping Up: A Gift From a Dying Star
The detection of disk-jet coprecession in AT2020afhd stands as the most compelling evidence to date for Lense-Thirring precession around a supermassive black hole . It confirms a 107-year-old prediction from general relativity. It gives us new tools to study black hole spin, accretion physics, and jet formation.
Most of all, it reminds us that the universe rewards those who keep watching.
At FreeAstroScience.com, we believe knowledge should be accessible to everyone. Complex ideas deserve simple explanations—not because readers can't handle complexity, but because clarity is a form of respect.
Keep your mind active. Keep asking questions. As Francisco Goya once warned: the sleep of reason breeds monsters. But when reason stays awake? It discovers wonders.
Come back soon. The universe isn't done surprising us.
Sources
- Wang, Y., et al. (2025). "Detection of disk-jet coprecession in a tidal disruption event." Science Advances, 11, eady9068. Published December 10, 2025.
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