Astronomers have found a supermassive black hole in the distant Universe that is blowing out a truly immense pair of jets, beams of matter and energy on a colossal scale: tip to tip, the jets measure a staggering 23 million light-years across. At least. 

OK, to get this in your brain we need to back up a bit and explain a few things [link to journal paper]. 

Black holes are pretty well known for pulling in material, not blasting it out, but in fact the vast majority of black holes we’ve detected are because of this phenomenon. The detailed physics of it isn’t totally understood, but the overview goes like this…

Supermassive black holes are found in the centers of galaxies, and can have masses of millions or billions of Suns. Huge. Each forms along with the host galaxy, affecting each other along the way. Matter in the galaxy, like clouds of dust and gas, can fall in toward the black hole. But that material has angular momentum, meaning as it orbits around the galaxy it wants to continue orbiting. As it falls in it speeds up, like an ice skater drawing in their arms in a spin. As the material gets near the black hole it settles into a disk, called an accretion disk, that in some cases can be hundreds of light years across.

Near the center the material is whirling around at nearly the speed of light, but farther out it moves more slowly. That means the particles in the disk rub against each other, creating friction on a mind-numbing scale. The heat generated can raise the temperature to millions of degrees, and the only thing keeping the disk together is its own gravity plus the constraining gravity of the black hole.

Hot material glows, and these disks can radiate away vast amounts of energy, easily outshining all the stars in the host galaxy. They also blast out X-rays, which is how many of these objects are found.

There are also ridiculously strong magnetic fields involved. The fields gets twisted up near the center of the disk, like batter being whipped by an overachieving electric mixer, strengthening so unbelievably they can actually dominate the material more than gravity does. They can then form two vortices, like magnetic tornadoes, each perpendicular to the disk right over the center. Material is drawn up into these vortices and blasted away at nearly the speed of light, creating twin beams astronomers call jets.

They can stay narrow for a long time because their internal magnetic fields keep them focused. Some in nearby galaxies to us are known to be millions of light-years long, but they’re usually rare. Most peter out before they get that long.

But.

A team of astronomers was using a radio telescope called LOFAR (LOw Frequency ARray) to look for cosmic structures in the early Universe, many of which emit radio waves. Specifically, they were hoping to map out the Cosmic Web, a series of long filaments of hydrogen that existed in the early days after the Big Bang, and which eventually formed clusters of galaxies that we see around us today.

Looking at the images, though, they saw a lot of giant black hole jets screaming away out of galaxies, far more than they expected. The jets emit radio waves as high-energy electrons spin along the magnetic field lines, creating what’s called synchrotron radiation, making them identifiable in radio telescope observations.

That’s when they stumbled on a pair of jets coming from a galaxy so far away the light from it took 7.5 billion years to reach us — we see it as it was 6.3 billion years after the birth of the Universe itself. The jets were each over 11 million light-years long, totaling 23 million easily, and may even be longer (we can’t see the third dimension in these observations, so if the jets are not pointed exactly 90° from us perspective shortens them). 

The astronomers nicknamed the structure Porphyrion, strongest of the mythological giants who battled the ancient Greek gods. Apt.

The jets are a mystery. How did they get so long? Usually instabilities in the gas stream robs the jets of their coherence before they get that big, so for some reason these jets are particularly stable. It’s possible the galaxy is steadily feeding the giant black hole in its core, and did so for a billion years before the light we see from it left. That means the black hole was stable as well, which is a little unusual…

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