About 3 billion years ago, an unfortunate star became caught in a twisting tug-of-war between two gigantic black holes, and now we’re seeing the faint screams of X-rays emanating from this violent event. If confirmed, it could be the most distant episode of two black holes attacking a star ever seen.
An international team of astronomers reported their decades-long observation of the faintest known variable X-ray flare in a paper accepted for publication in the journal The Innovation in November.
Make stellar spaghetti
A bright rise of X-rays followed by a long period of dimming is exactly what astronomers expect from violent encounters called tidal disturbance events (TDE), which occur when a star gets too close to a supermassive one. black hole. Before the star is swallowed by the monster’s event horizon (the point of no return), the black hole’s enormous gravity tears the star apart, a process cutely named “spaghettification,” as if the star were being dragged into a thin strand of pasta.
The stellar material then settles into a thin, rapidly rotating disk just outside the black hole. The energy released by this process heats the gas so much that it emits X-ray radiation that is visible even from the other side of the universe. The material then heads into the gaping maw of the black hole itself and the disk dims.
XID 925 was already notable, as it was one of the most distant and faintest TDEs ever recorded. But in 1999 everything went crazy.
Between January and March of that year, XID 925 brightened rapidly and unexpectedly by a factor of 27. Then, the X-ray brightness collapsed as quickly as it appeared, and
A consecutive attack of black holes
Now, the astronomers behind the new study believe there is another culprit behind this strange glow. This is not a simple case of a TDE around a single supermassive black hole. This is a case of TDE around two supermassive black holes.
They argue that the unfortunate star became trapped in the gravitational embrace of a gigantic central black hole and a smaller (but still large in its own right) companion black hole. The largest black hole tore the star apart and transformed it into an accretion disk. But then the second black hole approached the disk, or even passed through it, and this disturbance caused a furious explosion of energy, the scientists explained.
Like a hapless car crashing at the scene of an accident, the event further complicated the situation, in this case by causing the release of even more X-rays. Once the smaller black hole moved on, the system returned to normal.
While astronomers cautioned that this story does not perfectly explain all the data, they argued that it is the most compelling scenario given what we know. If true, it would be the most distant binary black hole tidal disturbance event known, giving us a crucial and exciting window into the complex relationships between stars and black holes at the hearts of young galaxies.
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