‘Planets are going to be destroyed’

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A jet of charged particles traveling at almost the speed of light, created from the remains of a star brutally torn apart by a supermassive black hole, turned out to be one of the brightest and most energetic events ever observed in the universe.

The jet, triggered by what astronomers call a tidal disruption event (TDE), is so powerful that it’s difficult to find a real phenomenon to compare it to. Thus, astronomers led by Yvette Cendes of the University of Oregon chose to compare it to the estimated energy production of a fictional device: Star Wars Death Star, which can blow up entire planets.

The TDE and associated jet release between 1,000 and 100,000 billion times more energy than fans claim the Death Star produces. And, as with the Death Star, any planets in the path of this jet are going to have a tough time.

“The planets will be destroyed during the first light years,Cendes, who is a radio astronomer, told Space.com. “I just don’t know how far from the jet that would be the case.”

More precisely, the total energy of this event, officially cataloged as AT2018hyz, depends on how this energy is emitted. Relativistic jets from TDEs are very rare, accounting for about 1% of all known cases. The remaining 99% is spherical flow that moves much more slowly. In the latter case, we would consider an energy production of 2 x 10^50 ergs (an erg is a unit of energy; the sun produces 10^33 ergs at its peak) while the jet scenario, which Cendes favors given the immense luminosity of AT2018hyz, would reach 5 x 10^55 ergs.

And energy production continues to increase. Models suggest it will peak in 2027 before gradually falling again.

“I’m hesitant to give a final energy estimate. There are too many things that it will depend on that will become clear once we actually see the peak,” Cendes said. “But we predict it will be about twice as bright at the summit as it is now.”

So how did this immense burst of energy come about? AT2018hyz was initially detected in 2018, and at the time it looked like a fairly ordinary TDE, of which just over 100 have been observed.

“There was nothing in that initial discovery that made us think something like this was going to happen years later,” Cendes said.

A TDE occurs when a star wanders a little too close to a supermassive black hole. In the case of AT2018hyz, the black hole resides in an otherwise fairly quiet location. galaxy 665 million light years away.

Tidal forces, whereby one side of the star feels a greater gravitational pull from the black hole than the opposite side, begin to stretch and tear the star in a vice-like grip, effectively shredding it.

For a few years after its initial discovery, not much happened to AT2018hyz. Astronomers aren’t sure why, but there is often a waiting period with TDEs. With this in mind, one hypothesis is that it takes a little time for the shredded stellar material to wrap around the black hole and form an accretion disk.

Some stellar matter falls into the black hole, but much of it is deflected away from the black hole by magnetic fields.

AT2018hyz was seen coming back to life in 2022, when it suddenly became bright in radio waves likely produced by the jet’s synchrotron radiation. This jet is so powerful that Cendes even nicknamed it “Jetty McJetface” — in reference to the famous Boaty McBoatface incident – ​​and it is currently 50 times brighter than when it was first detected. Seeing a black hole continue to emit so much energy so many years after consuming a star is considered unprecedented.

Another advantage of the jet explanation is that it would solve the mystery of why energy production continues to increase.

When such jets are first produced, they are highly collimated with a narrow opening angle, and if the jet was not pointed directly at us, but was at an angle to us, then we would not have seen its full blast. However, over time the jets tend to widen.

“And now it comes into our field of view as the jet decelerates,” says Cendes. “As for how you get these relativistic jets from a TDE, no one knows for sure, but it’s an active area of ​​research. It probably has something to do with magnetic fields, but clearly there have to be other things happening as well, otherwise we’d see them more frequently in TDEs.”

Now, Cendes wants to look for more of these exceptionally energetic events. With the Square Kilometer Array (SKA) coming online over the next decade, astronomers will finally have a tool capable of studying the radio sky with great precision and sensitivity, potentially finding many more radio jets not only from TDEs, but also from galaxies that are more regularly active.

The findings of the Cendes team were published on February 5 in The Astrophysics Journal.