A supermassive black hole roughly 660 million light-years from Earth has been caught firing off a blast of energy that dwarfs anything the Death Star could manage, and the outburst did not even start until years after the initial destruction. The event, cataloged as AT2018hyz, involves a star torn apart by a black hole’s gravity in what astronomers call a tidal disruption event, or TDE. What makes this case extraordinary is not just the raw power involved but the fact that the energy output keeps climbing more than five years after the star was first shredded.
A Star Ripped Apart in 2018, Still Brightening Today
The All-Sky Automated Survey for Supernovae, known as ASAS-SN, first spotted AT2018hyz (also designated ASASSN-18zj) in October and November 2018. Early observations captured the optical flare typical of a star being pulled apart, and the host galaxy sits at a redshift of z≈0.04573, placing it in a relatively nearby corner of the universe by cosmological standards. Initial multiwavelength photometry, X-ray spectra, and radio upper limits painted a picture consistent with a standard TDE: a brief, violent flash followed by a gradual fade.
That picture turned out to be incomplete. Late-time radio and millimeter observations spanning roughly 970 to 1,300 days after the disruption revealed something unexpected: the radio signal was not fading. Instead, it was rising sharply, following a steep power-law curve of approximately t to the fifth power, according to early modeling work based on these delayed data. That rate of brightening is flatly inconsistent with any outflow launched at the moment the star was torn apart. Something new had switched on hundreds of days later, indicating that the black hole, debris system was far more dynamic on multi-year timescales than standard theories had assumed.
A Delayed Blast With 100 Times the Death Star’s Power
The most recent radio observations, covering roughly 1,370 to 2,160 days after disruption, show that the brightening has continued across all observed frequencies. The luminosity has reached approximately 1040 erg per second, a figure drawn from multi-frequency radio measurements analyzed by a team that tracked AT2018hyz long after most TDEs would have faded from view. To translate that into terms a broader audience can grasp, researchers at the University of Oregon framed the output as exceeding what the fictional Death Star could produce by a factor of roughly 100, underscoring how extreme even “ordinary” black holes can be, when they feed.
The pop-culture comparison is eye-catching, but the underlying physics carries more weight. The delayed launch of the outflow, estimated at around 750 days after optical discovery, means the black hole did not simply blast material outward during the initial tidal shredding. Instead, a significant delay separated the destruction of the star from the generation of this powerful outflow, implying that the debris needed time to circularize, settle, and perhaps reconfigure before driving a large-scale jet or wind. That timeline gap is the central puzzle driving current research, because standard TDE models do not predict such a long dormancy before a major energy release, suggesting that accretion disks around supermassive black holes may evolve in more episodic and unstable ways than previously thought.
Competing Explanations for the Late Radio Flare
Two primary models are competing to explain what is happening. The first proposes a mildly relativistic outflow that was launched well after the disruption, possibly as accumulated stellar debris finally formed a structured accretion disk and funneled material into a jet. The steep t-to-the-fifth rise supports this interpretation because it implies a fresh injection of energy rather than a gradually decelerating blast from 2018, and it naturally accounts for the lack of early radio emission: the outflow simply did not exist yet. In this picture, the black hole’s feeding process resembles a delayed ignition, where the most efficient energy extraction switches on only after the system has had years to reorganize.
The second model, detailed in a separate off-axis jet analysis, argues for a relativistic jet that was launched closer to the time of disruption but was initially aimed away from Earth. As the jet expanded and decelerated, its emission cone widened enough for the signal to reach our telescopes, producing the appearance of a delayed flare without requiring a truly late launch. Neither model has been definitively ruled out, and each carries testable predictions about radio spectral evolution, polarization, and the eventual turnover of the light curve. One angle that neither framework has fully addressed is whether a precessing jet, one that wobbles as it interacts with surrounding material, could produce the observed brightening pattern along with distinctive polarization signatures that future instruments might detect, offering a third way to reconcile the data.
Why TDE AT2018hyz Rewrites the Playbook
Most tidal disruption events follow a relatively predictable arc. A star wanders too close to a supermassive black hole, gets stretched and torn by tidal forces, produces a bright optical and X-ray flare, and then fades over weeks to months as the debris is swallowed or blown away. AT2018hyz broke that script by staying radio-quiet for years and then surging to luminosities that rival some of the most energetic astrophysical phenomena known, blurring the line between “thermal” TDEs and jet-dominated explosions. The fact that the radio emission is still climbing more than five years out challenges the assumption that TDEs are transient events with short-lived aftermaths and suggests that their true energy budgets may be systematically underestimated when observations stop too soon.
This matters beyond a single unusual object. Upcoming survey telescopes, including the Rubin-era facilities that will scan the sky for changing objects, are expected to detect TDEs at far higher rates than current instruments. If delayed outflows or off-axis jets are common features of these events, the astronomical community will need monitoring strategies that extend years beyond initial discovery and coordinate radio, optical, and X-ray follow-up. Long-baseline projects will require not only telescope time but also robust logistical support, from data pipelines to administrative infrastructure akin to the services universities provide through resources like the One-Stop student portal, underscoring how sustained, organized effort is essential to capture the full life cycle of rare cosmic explosions.
What the Ongoing Brightening Means for Future Observations
The continued rise in radio luminosity across all frequencies raises a practical question: when will it peak? The multi-frequency data collected through roughly 2,160 days post-disruption show no sign of a turnover yet, indicating that the shock front or jet responsible for the emission is still efficiently energizing particles in the surrounding medium. If the outflow is still accelerating or if fresh material continues to be fed into the jet, the source could brighten for years to come, turning AT2018hyz into a long-lived beacon that maps the density and structure of gas around its host galaxy’s central black hole. Continued monitoring with radio arrays will be crucial to determine whether the light curve eventually flattens, steepens, or oscillates, each outcome favoring different physical interpretations.
For observers planning the next decade of time-domain astronomy, AT2018hyz functions as both a warning and an invitation. It warns that short campaigns risk missing delayed, high-energy phases that may dominate an event’s total output, and it invites more ambitious, multi-year programs that treat TDEs as evolving laboratories rather than one-off flashes. Building those programs will depend on training new researchers, supporting them through opportunities such as graduate admissions and funding, and ensuring they have access to observatories and collaboration networks, much as campus visits are used to connect prospective students with resources via organized outreach events. As AT2018hyz continues to brighten, it also strengthens the case for philanthropic investment in long-term monitoring efforts, echoing the role of donor-supported initiatives such as university giving programs that underwrite sustained scientific projects whose most exciting results may not emerge until years after the initial spark.
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*This article was researched with the help of AI, with human editors creating the final content.
