An enduring astronomical mystery has deepened yet again. Peculiar one-dimensional strands that extend up from the galactic core are not alone, according to a new paper out today. Astronomers have discovered shorter, dashlike horizontal strands as well. Like the others, they are difficult to explain.

Northwestern University astronomer Farhad Yusef-Zadeh discovered the vertical strands, or filaments, in the 1980s and greatly expanded their known ranks in 2022, to about 1,000. When he found the horizontal ones fanned out to one side of the galactic core, it took him by surprise.

“I’m used to them being vertical,” he says in a press release. “I never considered there might be others along the [galactic] plane.”

What Are the Galactic Filaments Made Of?

The vertical strands extend up to a massive distance – some 150 light-years, about 240,000 times the distance from the sun to Pluto.

These filaments appear to be composed of huge amounts of cosmic ray electrons moving at close to the speed of light. And, most perplexingly, they often appear “stacked equally spaced, side by side like strings on a harp,” according to a 2022 press release.

How Many Strands Exist?

The horizontal strands number far fewer, just a few hundred, and they’re only 5 to 10 light-years in length. They radiate out to one side of the galactic plane like spokes on a wheel and appear to emit thermal radiation.

“I was actually stunned when I saw these,” says Yusef-Zadeh in a press release. “We had to do a lot of work to establish that we weren’t fooling ourselves.”

He and other researchers made the discovery by piecing together data from the MeerKAT radio telescope in South Africa. The trick lay in filtering out all the other galactic noise to hone in on the strands, which came through as a colorful tapestry.

“It’s like modern art,” Yusef-Zadeh says in a press release.

Read More: Astronomers Find Four Strange New Objects in the Center of the Milky Way

Where Did These Galaxy Filaments Come From?

He has hypothesized that the lines originally sprang from the supermassive black hole at the center of our galaxy, Sagittarius A*. The vertical strands hang around it like tinsel, and black holes sometimes eject gases in dramatic outflows.

“Black holes are like powerful vacuum cleaners that eject some of the dirt that gets near them instead of sucking in everything,” says Marco Ajello, an astrophysicist at Clemson University, in a press release. The ionized gas collides with other matter in the galaxy, creating cosmic rays not unlike those in the vertical strands.

“We think [the strings] must have originated with some kind of outflow from an activity that happened a few million years ago,” Yusef-Zadeh says.

There are other, less serious possibilities, such as the explanation that the strands are somehow exhausted from huge alien spacecraft. But he’s not taking that theory seriously.

“Certainly [those speculations] are sci-fi,” Yusef-Zadeh told Discover in a 2022 interview.

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