A field of thirty-six radio antennas has been silently scanning the sky at a remote location called Inyarrimanha Ilgari Bundara in Western Australia’s red desert. They aren’t specifically searching for anything, but they are keeping an eye out for things that weren’t there before. By astronomy’s standards, that kind of patient, wide-field searching is unglamorous work. No single goal, no splashy target. Week after week, just methodical sky coverage while we wait for something unexpected to happen in the universe. It did in the latter part of last year. Additionally, the data revealed something so peculiar that the researchers who discovered it are still figuring out all the ramifications.
Prior to an explanation, the signal was identified as ASKAP J005512-255834, which is situated approximately 1.7 billion light-years away from Earth in a small, irregular galaxy. The Australian SKA Pathfinder radio telescope discovered a source that had just materialized, brightening quickly and releasing energy at a rate equal to the combined radio output of billions of suns before starting a gradual fade that has persisted for more than a thousand days.
Key Facts: The Unexplained Cosmic Explosions
| Event 1 — “Orphan Echo” | Radio signal ASKAP J005512-255834 — detected by Australian SKA Pathfinder (ASKAP); identified as the echo of a gamma-ray burst that was never directly observed |
| Echo’s energy output | ~10³² joules per second — equivalent to the combined radio output of billions of suns; visible in radio waves for over 1,000 days |
| Host galaxy location | Small, irregular, star-forming galaxy approximately 1.7 billion light-years from Earth |
| Detection instrument | ASKAP — 36-antenna radio telescope at Inyarrimanha Ilgari Bundara, Western Australia; operated by CSIRO |
| Lead researchers | Ashna Gulati (PhD Candidate) & Prof. Tara Murphy — both Radio Astronomy, University of Sydney |
| Event 2 — GRB 250702B | Gamma-ray burst first detected July 1–2, 2025 by Einstein Probe & NASA’s Fermi telescope; lasted nearly a full day — unprecedented in 50 years of GRB observation |
| Why it’s unusual | Repeated in periodic bursts — never seen before; standard GRBs last milliseconds to minutes and do not recur |
| Possible explanations | Death of a ~40-solar-mass star (unusual type); or tidal disruption event involving an intermediate-mass black hole — a class never directly confirmed |
| Study co-lead | Antonio Martin-Carrillo — astrophysicist, University College Dublin; published in The Astrophysical Journal Letters (Aug. 29, 2025) |
| Reference | The Conversation — Original Research Report |
At other wavelengths, it barely left a trace. no equivalent in visible light. There is no X-ray signal. It was just this persistent, fading radio glow that behaved like the long echo of something that had already ended by the time anyone noticed it. The researchers who discovered and described the signal, Ashna Gulati and Tara Murphy of the University of Sydney, think they may have discovered what astronomers have been speculating about for decades but have been unable to find: a “orphan afterglow,” the fading radio echo of a gamma-ray burst whose initial blast was directed away from Earth and thus never directly detected.
After the Big Bang, gamma-ray bursts are the universe’s strongest explosions. They happen when black holes are created when massive stars collapse, releasing concentrated jets of high-energy radiation that, in a matter of seconds, release more energy than the Sun will over the course of its multi-billion-year existence. Orientation is the catch.
They’re narrow jets. We are unable to see the initial flash if it is not directed toward Earth. However, as the blast wave slows, spreads, and illuminates the surrounding gas and dust, astronomers have long predicted that the afterglow of such an explosion should eventually become detectable even when the jet wasn’t pointing our way. The echo is that fading glow. And if the researchers’ interpretation is correct, ASKAP J005512-255834 is the most obvious example of one ever discovered; it is only the second candidate ever discovered and what Gulati and Murphy refer to as the most convincing orphan afterglow candidate to date.
The event might be explained by something even more bizarre: an intermediate-mass black hole, a type of object that has been hypothesized for decades but never proven to exist, could be tearing apart a star. In any case, the galaxy that is home to this transient is a small, irregularly structured system that is actively forming stars, which is precisely the kind of setting where extreme stellar deaths typically occur.
Already, the story of the orphan afterglow is amazing. However, it came with something perhaps more confusing. The Einstein Probe, a Chinese and European X-ray space telescope, and NASA’s Fermi Gamma-ray Space Telescope independently discovered a gamma-ray burst in July of last year that just wouldn’t behave like one. The event, officially known as GRB 250702B, erupted repeatedly over the course of almost a full day in what appeared to be a periodic pattern. Not a single flash of catastrophe. frequent outbursts. ones that are periodic.
It was unlike anything seen in fifty years of gamma-ray burst observations. According to Antonio Martin-Carrillo, an astrophysicist at University College Dublin who co-led the study, the event confused scientists not only because of its length but also because periodicity had never been observed in a gamma-ray burst before. The source that initiates the burst does not survive it, according to the conventional model for these occurrences, which is a one-time disaster. Periodic, recurrent behavior doesn’t fit that description at all.
The scientists investigating these occurrences feel that they might be examining the boundaries of what existing astrophysical models can account for. Explanations for GRB 250702B include either something involving an intermediate-mass black hole or the death of a star about forty times the mass of the Sun, though this is a very unusual type.
It is suggestive in and of itself that anomalies at the extreme end of the energy scale continue to be explained by the intermediate-mass black hole. It’s difficult to ignore the fact that the universe appears to be producing two events that are difficult for current theory to satisfactorily explain, both of which may be related to the same class of poorly understood object.
It’s still unclear if these findings will eventually necessitate a reworking of the underlying physics or if they will eventually fit into preexisting frameworks that have been expanded and modified to take into account the new information. Science often does both, sometimes at the same time.
It is evident that modern instruments, such as space-based X-ray observatories, patient radio surveys, and quick optical follow-up with devices like the Very Large Telescope in Chile’s Atacama desert, are capturing information that earlier generations of astronomers were unable to. The most extreme moments of the universe have been concealed in plain sight. At last, the listening apparatus is capable of detecting the echoes.
