A Supermassive Black Hole Shredded a Star — and Is Still Burping Out Its Bright Remains
A supermassive black hole that tore apart a star years ago is now blasting out energy that rivals a gamma-ray burst, potentially making it one of the most powerful single events ever detected in the universe. Instead of fading after its initial flare, the system has continued to brighten, defying expectations about how these cosmic catastrophes unfold.
In a new study published in The Astrophysical Journal, researchers report that the object, known as AT2018hyz, has grown roughly 50 times brighter in radio wavelengths since it was first detected. The emission is still rising and could peak around 2027.
“This is really unusual,” said research lead Yvette Cendes in a press release. “I’d be hard-pressed to think of anything rising like this over such a long period of time.”
Read More: Supermassive Black Hole Flare Launched Wind and Debris Into Space at 37,000 Miles Per Second
Tidal Disruption Events Near Supermassive Black Holes
Events like this begin with what astronomers call a tidal disruption event. If a star passes within reach of a supermassive black hole, gravitational forces stretch it unevenly, pulling harder on the near side than the far side until the star is torn apart. The nickname “spaghettification” captures the visual: the star is drawn out into elongated streams of gas.
Some of that stellar debris forms a swirling disk around the black hole, heating up as it falls inward and emitting light across multiple wavelengths. In most known cases, the emission peaks relatively quickly and fades within months.
That is why AT2018hyz did not initially stand out. When optical surveys identified it in 2018, it behaved like a typical disruption. There was no early indication that it would later produce an unusually strong and persistent radio signal. Only years later did radio observations reveal that something much less ordinary was happening.
A Black Hole Jet Growing Brighter in Radio Waves
The steady rise in radio brightness suggests the black hole launched a jet, a narrow stream of high-energy particles shooting outward from its vicinity. Jets form when powerful magnetic forces redirect some of the falling gas away from the black hole instead of letting it all disappear inside.
What distinguishes this case is not simply the presence of a jet, but its timing. Instead of appearing immediately after the star’s destruction, the radio emission strengthened gradually and has continued to intensify over several years. Current models indicate it may keep rising before reaching a maximum around 2027.
One explanation is geometric. If the jet was not originally pointed toward Earth, its signal may have been faint or undetectable at first. As it expands or changes orientation, more of its radiation could now be entering our line of sight.
Data gathered from radio facilities in New Mexico and South Africa show that the outflow’s energy rivals that of gamma-ray bursts, among the most luminous explosions known. By comparison, even the fictional Death Star from Star Wars would register as insignificant next to this real cosmic event.
Rethinking Long-Term Black Hole Emissions
The prolonged brightening forces a reconsideration of how tidal disruption events evolve. They have often been categorized as brief transients that fade quickly after their initial flare. AT2018hyz suggests the most energetic phase may unfold on a much longer timescale.
That possibility carries practical implications. Telescope time is limited, and once a disruption appears to fade, long-term monitoring is uncommon. If similar late-stage jets exist elsewhere, they may have gone unnoticed simply because observations stopped too soon.
For now, AT2018hyz is still being monitored as its radio output rises. Whether it is an outlier or part of a broader pattern, it suggests that the aftermath of stellar destruction can unfold over years and only becomes clear with sustained observation.
Read More: Black Hole Reawakens Like a Cosmic Volcano After 100 Million Years of Sleep
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