Astronomers have identified what may be the first clear example of a radio galaxy whose central black hole produced four distinct episodes of powerful jet activity. The object, J023721.13−010528.5, is a giant S-shaped radio galaxy hosted by a massive elliptical galaxy at a redshift of about 0.372. Its outer radio structures span roughly 1.2 megaparsecs, or nearly 3.9 million light-years.
The result comes from observations made with the upgraded Giant Metrewave Radio Telescope in India and combined with radio data from MeerKAT and the Very Large Array. Pavan Vijay Khadekar, Dharam Vir Lal and Ramana Athreya report four pairs of radio components arranged on opposite sides of the galaxy’s core. Each pair appears to represent a different episode in which the central supermassive black hole launched relativistic jets into surrounding space.
Radio galaxies are powered by active galactic nuclei. Matter falling toward a supermassive black hole forms an accretion structure and can generate narrow jets of plasma moving at relativistic speeds. In powerful Fanaroff–Riley type II radio galaxies, those jets can terminate in luminous hotspots where the outflow interacts with the surrounding medium.
What makes J023721.13−010528.5 unusual is not simply that it has large jets. Astronomers already know examples in which a black hole appears to restart after a dormant period. These are called double-double radio galaxies because two distinct pairs of radio lobes preserve evidence of two separate activity cycles. A smaller number of triple-double systems have also been identified. The new object appears to preserve four.
The team labels the structures N1–N4 and S1–S4 on opposite sides of the core. Multi-frequency observations show that the radio emission becomes progressively older with increasing distance from the center. The estimated spectral ages range from roughly 4.5 million years for the younger structures to about 20.5 million years for the oldest. This age progression is one of the strongest arguments that the features are remnants of separate jet episodes rather than random bright knots inside a single continuously active outflow.
The researchers also examined the symmetry of the structures. According to their statistical analysis, the interpretation involving three inner pairs of recurrent hotspots is around three million times more likely than a model in which those features are merely random knots in an uninterrupted jet. On that basis, they propose J023721.13−010528.5 as the prototype of a new class: a “quadruple-double radio galaxy.”
The geometry tells another part of the story. Successive hotspot pairs are not perfectly aligned. Their axes rotate progressively, producing the source’s large S-shaped appearance. The authors suggest that this may reflect gradual precession or wobbling of the central black hole’s jet axis over millions of years. The galaxy therefore records not only repeated activity, but also a changing direction of activity.
The study is currently available as a preprint and is listed as accepted for publication in The Astrophysical Journal. That distinction matters. The observational pattern is strong enough for the authors to argue for four separate episodes, but the object remains a single example. Further systems will be needed before astronomers can determine how common this behavior is or which physical mechanisms control the periods of activity and silence.
The discovery adds to a broader change in the way black holes are understood. A supermassive black hole is not simply an object that is either “active” or “inactive.” Its visible behavior can unfold in cycles. Gas supply can change, accretion can weaken or intensify, and jets can disappear and later return. On human timescales the galaxy looks almost perfectly static. On million-year timescales it has a history.
That difference in scale is the most interesting philosophical consequence of the finding. Human perception naturally divides reality into objects: a star, a galaxy, a black hole. Astronomy repeatedly shows that these apparent objects are better understood as processes. Their identities include events that happened long before the present light reached us and structures that preserve different phases of an evolving system.
In J023721.13−010528.5, the outer radio structures can be read almost like geological strata. Each pair is a surviving trace of an earlier state of the same central engine. The galaxy therefore makes visible something that is normally difficult to imagine: one astronomical object containing several different eras of its own activity at the same time.
This also changes what “silence” means in the cosmos. A dormant black hole is not necessarily finished. A vanished jet may be a pause rather than an ending. The universe contains systems whose present state cannot be understood without reconstructing cycles of activity separated by millions of years.
Templum Dianae has recently covered another frontier where the visible universe points toward hidden structures: the search for direct evidence of dark matter. The two stories concern very different branches of astrophysics, but both illustrate the same limitation of ordinary perception. Much of the universe is reconstructed indirectly, through traces, interactions and patterns left behind by processes that cannot be observed directly in real time.
The deeper question raised by the new radio galaxy is therefore not only how often black holes restart. It is how much of reality appears permanent simply because our lives are too short to see its transformations.
References
https://arxiv.org/abs/2609.08506
https://phys.org/news/2026-09-astronomers-radio-galaxy-evidence-jet.html
https://astrocurrent.com/giant-radio-galaxy-four-jet-episodes/