A black hole radio outburst in a distant spiral galaxy has lasted far longer than astronomers expected. The galaxy, known as SDSS J110546.07+145202.4, is located about 1.8 billion light-years away in the constellation Leo, and its radio emission has remained unusually bright for more than eight years. Most radio transients linked to galactic centers fade within days or weeks, but this one has not. In this article, we will explore what astronomers found, why this black hole is unusual, and how a nearby galaxy may help explain black holes from the early universe.
Section 1 — A Radio Signal That Refused to Fade
Most galaxies are not quiet. Their stars emit light, their gas moves, and their central black holes can sometimes flare when matter falls inward. But in radio astronomy, some events stand out because they change quickly.
These are called radio transients. They are short-lived sources of radio emission that appear, brighten, and then fade. When they occur near the centers of galaxies, they can be connected to extreme activity around supermassive black holes.
That is why SDSS J110546.07+145202.4 is so unusual.
Astronomers found that this spiral galaxy became dramatically brighter in radio wavelengths. Its radio emission increased by more than 20 times in a short period, and instead of fading away, it stayed bright for years. According to the research team, the galaxy has been shining exceptionally strongly in radio light for more than eight years, reaching about 10 quadrillion times the radio brightness of the Sun.
That duration is the key.
A normal radio transient associated with a galactic center might last days or weeks. This one has lasted long enough that astronomers are treating it as the prototype of a possible new class of galaxies: systems that undergo rapid but long-lasting changes in radio emission.
The source of the emission appears to be close to the galaxy’s central black hole. This is not simply a galaxy becoming slightly brighter across all wavelengths. The radio signal points to a specific process happening near the black hole, where gravity, hot gas, magnetic fields, and high-energy particles interact.
The galaxy was studied by an international team led by Stefanie Komossa from the Max Planck Institute for Radio Astronomy. The team combined new observations with archival data across a wide range of wavelengths, from low-energy radio waves to high-energy X-rays. Their results were published in The Astrophysical Journal.
The object is also described as a long-duration radio changing-look NLS1 galaxy. NLS1 stands for narrow-line Seyfert 1, a type of active galaxy often linked to relatively low-mass but rapidly growing central black holes.
That detail matters because this is not just a bright radio source. It is a black hole system that appears to be changing state.
And that raises the main question: what happened near this black hole that allowed the radio outburst to last for so long?
Section 2 — Why This Black Hole Radio Outburst Is Different
The black hole at the center of SDSS J110546.07+145202.4 is described as comparatively low in mass, but it is growing very quickly by pulling in matter. This process is called accretion. When gas falls toward a black hole, it heats up, compresses, and releases enormous amounts of energy. In some cases, part of that energy can power a jet — a narrow beam of particles traveling at nearly the speed of light.
The team suspects that more matter has been falling into the black hole for several years. That enhanced feeding may have triggered a jet, which then produced the long-lasting radio emission. But the reason the black hole began receiving more matter — and why the outburst has remained bright for so long — is still not fully known.
This is where the discovery becomes more important than a single bright signal.
A jet is not just a cosmic flashlight. It is a sign that the black hole’s environment has changed. Matter near the black hole must be arranged in a way that allows powerful magnetic and energetic processes to launch material outward.
That is difficult to study because the region near a black hole is small, distant, and extreme. Astronomers cannot watch the gas fall in directly the way they might track weather patterns on a planet. Instead, they use radio, optical, ultraviolet, and X-ray signals to reconstruct what is happening.
In this case, follow-up observations involved multiple facilities, including the 100-meter Effelsberg radio telescope, the Australia Telescope Compact Array, and space-based satellites. These observations helped confirm the unusual properties of the source.
The black hole radio outburst is also unusual because luminous radio emission from rapidly growing lightweight black holes is rare. Seeing such an object transition into a long-lasting radio-bright state had not been observed before, according to the study team.
That makes the galaxy important for two reasons.
First, it gives astronomers a nearby example of a black hole that may be switching into a jet-producing state.
Second, it may reveal how smaller, rapidly growing black holes behaved when the universe was young.
This does not mean SDSS J110546.07+145202.4 is located in the early universe. It is not. At about 1.8 billion light-years away, it is relatively nearby compared with the most distant galaxies JWST and radio telescopes study.
But its central black hole has properties astronomers associate with early cosmic history: lower mass and rapid growth.
That combination makes the galaxy a kind of local laboratory.
Section 3 — A Nearby Window Into the Early Universe
The early universe was filled with growing galaxies and feeding black holes. Astronomers know that some supermassive black holes became enormous surprisingly quickly, but the steps between small black hole seeds and massive active galactic nuclei are still not fully understood.
One missing piece is how low-mass black holes grow rapidly and begin launching powerful jets.
SDSS J110546.07+145202.4 could help with that.
Because the galaxy is much closer than ancient high-redshift galaxies, astronomers can study it in more detail. It gives them a chance to observe a black hole with early-universe-like behavior without needing to look across nearly the entire observable universe.
That is why this black hole radio outburst matters. It is not only bright. It is accessible.
The team describes the galaxy as a nearby system that may help researchers understand black hole growth and jet formation, especially because low mass and rapid growth are exactly the types of properties expected in central black holes in young galaxies.
The next step is resolution.
Future high-resolution observations with instruments such as the Very Long Baseline Array may allow astronomers to map the structure of the jet and track how the radio emission evolves in the coming years. If the outburst continues, scientists could watch the system change in real time on astronomical timescales.
That is rare.
Many cosmic events are discovered after their most important stage has already passed. A star explodes, a flare fades, or a transient disappears before enough data can be collected. But this source has stayed bright long enough for astronomers to keep studying it.
That gives researchers a chance to answer several questions.
Is the jet newly formed, or did an older jet suddenly become brighter? Is the black hole receiving a fresh supply of gas from the galaxy? Did an instability in the accretion disk trigger the outburst? Or is this a longer transformation in how the black hole feeds and releases energy?
At the moment, the answer is not settled.
That uncertainty is the point. The object is valuable because it is not behaving like the short radio transients astronomers already know. It has created a new observational problem.
And future surveys may reveal that it is not alone.
The upcoming Square Kilometre Array telescopes are expected to identify more radio transients in future sky surveys. If similar objects are found, astronomers could begin to build a population of long-lived radio-bright black holes and compare them across different masses, galaxies, and environments.
That would help answer a deeper question: how common is this phase in black hole growth?
If it is rare, SDSS J110546.07+145202.4 may be an exceptional object caught during an unusual event. If it is more common, then astronomers may have been missing an important stage in the life of growing black holes.
Either way, the discovery is useful.
It shows that some black holes can enter a radio-bright state and remain there for years. It suggests that long-duration radio outbursts may reveal how jets are born or sustained. And it gives astronomers a nearby system that resembles the kind of black hole growth expected in the early universe.
The black hole has not solved the mystery yet.
But by refusing to fade, it has given scientists something rare: time.
Conclusion
A black hole radio outburst in SDSS J110546.07+145202.4 has stayed bright for more than eight years.
Its low-mass, fast-growing black hole may resemble the black holes expected in young galaxies.
Now astronomers have a nearby laboratory for studying how black holes grow, launch jets, and shape the evolution of galaxies.
