Imagine a cosmic vacuum cleaner so powerful it makes the Death Star look like a toy! Four years ago, astronomers witnessed something truly astonishing: a supermassive black hole, a cosmic behemoth, actively devouring an entire star. This dramatic event, known as a tidal disruption event (TDE), occurred when a star strayed too close to the black hole's immense gravitational pull, sealing its fate. What's even more mind-boggling is that the energy unleashed by this cosmic meal is still on the rise, years later.
This particular stellar drama is designated AT2018hyz. The name might sound technical, but it simply breaks down as follows: 'AT' stands for Astronomical Transient, '2018' marks the year it was first noticed, and 'hyz' is a unique identifier for that year. While the initial optical detection happened in 2018, it wasn't until 2022 that astronomers picked up the significant radio emissions emanating from this event. These new findings are detailed in a recent publication in The Astrophysical Journal, spearheaded by lead author Yvette Cendes, an Assistant Professor at the University of Oregon.
Cendes and her team have been meticulously observing AT2018hyz, and their latest research, covering observations from roughly 1370 to 2160 days after the initial disruption, reveals a startling trend: the energy output continues to climb across all radio frequencies. This is quite unlike typical TDEs, which usually fade after their initial burst of activity.
But here's where it gets controversial... When AT2018hyz was first observed in optical light back in 2018, it appeared as just another TDE. It was only later, when Cendes re-examined it, that the immense radio energy became apparent. A previous paper on this peculiar event noted that such a sustained and steep rise in emissions couldn't be explained by an outflow launched at the time of the star's destruction, strongly suggesting a delayed launch of this energetic phenomenon. The latest findings confirm this, showing that the energy emitted by the black hole has become a staggering 50 times brighter since its initial radio detection.
So, what's causing this prolonged energy surge? Scientists have proposed two main theories. The first is a 'delayed spherical outflow.' This suggests that the material ejected by the black hole wasn't sent out immediately but rather about 620 days after the star was torn apart. The researchers' analysis of the outflow's physical expansion supports a launch that occurred approximately 1.7 years after the initial optical sighting.
The second, and perhaps more dramatic, explanation is an astrophysical jet. This jet would be traveling at nearly the speed of light (relativistic speeds) and would be viewed from an angle significantly off its direct path. From our distant vantage point, the intense beaming of energy from such a jet would initially be suppressed, but as it slows down and spreads out, its radio emissions would rapidly increase – precisely what is being observed.
And this is the part most people miss... The research indicates that this stream of radio waves is expected to continue its ascent, potentially peaking in 2027. Lead author Yvette Cendes herself expressed her astonishment, stating, 'I'd be hard-pressed to think of anything rising like this over such a long period of time.'
When the scientists crunched the numbers to quantify the black hole's energy output, they were met with another surprise: it's comparable to the energy released by a gamma-ray burst (GRB), which are among the most powerful explosions in the universe. To put this into perspective, the researchers playfully compared its power to the Death Star from Star Wars. Their calculations suggest this supermassive black hole is emitting at least one trillion times more energy than the fictional superweapon, and possibly as much as 100 trillion times more!
However, these are calculations made from an immense distance, and only continued observation can confirm their accuracy. This groundbreaking discovery also opens up a crucial question: are other black holes and TDEs out there exhibiting similar delayed and rising radiation patterns? The honest answer is, we don't know, as such phenomena haven't been extensively searched for. As Cendes wisely put it, 'If you have an explosion, why would you expect there to be something years after the explosion happened when you didn't see something before?'
While AT2018hyz isn't the only TDE with delayed radio emissions, its luminosity is exceptionally high compared to others. The researchers are planning to continue monitoring AT2018hyz across various frequencies to better understand the evolution of the outflow and its surrounding environment.
What do you think? Does the idea of a black hole outshining the Death Star by trillions of times spark your imagination, or does it seem too fantastical? Share your thoughts below!
