Other Weird Cosmic Threads Discovered Outside Our Galaxy, and They're Huge

Other Weird Cosmic Threads Discovered Outside Our Galaxy, and They’re Huge

We are getting closer to solving the strange mystery presented by hundreds of enormous filaments hanging from the heart of the Milky Way.

For the first time, these long magnetized filaments glowing in radio waves have been observed emerging from other galaxies. Not only are they no longer unique to the Milky Way, but the range of environments in which they can be found allows scientists to narrow down the mechanisms that create them.

Astrophysicist Farhad Yusuf-Zadeh of Northwestern University in the United States first discovered the filaments of the Milky Way in the 1980s and has been questioning them ever since.

According to Yusuf-Zadeh, there are two possible explanations. The first is an interaction between galactic winds and large clouds; the second is turbulence in weak magnetic fields agitated by the movement of galaxies.

“We know a lot about filaments in our own galactic center, and now filaments from outer galaxies are starting to appear as a new population of extragalactic filaments,” Yusuf-Zadeh said.

“The underlying physical mechanisms of the two populations of filaments are similar despite very different environments. The objects are part of the same family, but filaments outside the Milky Way are older and more distant cousins ​​- and i mean very distant cousins ​​(in time and space)”.

About 1,000 of the filaments, measuring up to 150 light-years in length and suspended in eerily neat and orderly arrangements like harp strings, have been discovered in the Milky Way so far, most recently thanks to the MeerKAT radio telescope in Africa. from South.

Sensitive telescope observations of the Galactic Center – penetrating through the thick dust and gas that obscures much of what’s inside – have increased the number of previously known filaments tenfold. These radio observations also revealed that the filaments contain cosmic ray electrons spinning in magnetic fields at nearly the speed of light, and that the magnetic fields are amplified along the entire length of all the filaments.

Some of the recently discovered filaments from a galaxy 246 million light-years away. (Yusuf-Zadeh et al.)

Without more information, figuring out why they’re there, quietly hanging out in the galactic center, was going to be tricky. The discovery of more filaments, in four different galaxy clusters located between 163 million and 652 million light-years away, is a huge breakthrough.

“After studying the filaments in our own galactic center for all these years, I was extremely excited to see these extremely beautiful structures,” says Yusuf-Zadeh. “Because we found these filaments elsewhere in the Universe, it hints that something universal is going on.”

The newly discovered filaments outside the Milky Way differ from the threadlike structures of our galaxy in several rather important ways. They are associated with jets and lobes of radio galaxies – huge structures that erupt from the galactic center, extending vast distances on either side of the galactic plane. The filaments extending from these jets and lobes are also much larger than structures seen in the center of the Milky Way – between 100 and 1,000 times larger.

“Some of them are incredibly long, up to 200 kiloparsecs,” says Yusuf-Zadeh.

“It’s about four or five times larger than the size of our entire Milky Way. What’s remarkable is that their electrons stick together on such a long scale. If an electron traveled at the speed of light the along the filament, it would take 700,000 years. And they don’t travel at the speed of light.”

Filaments extending at roughly right angles from the jet of a radio galaxy. (Rudnick et al.)

They are also older and their magnetic fields are weaker. And, of course, they extend into intergalactic space, often at right angles to the jets. The filaments of the Milky Way seem to be centered on the galactic disk.

However, the similarities are strong. Galactic and extragalactic filaments have the same length-to-width ratio, and the cosmic ray transport mechanism is the same. If the same mechanism produces all the filaments, it must be something that works at different scales.

Winds could be one such mechanism. Active supermassive black holes and rampant star formation can generate galactic winds that blow through intergalactic space. These winds could push through the tenuous clouds of gas and dust that drift through interstellar and intergalactic space, pushing material together to create filamentary structures.

The simulations suggested another possibility: turbulence in the medium, generated by gravitational disturbances. This turbulence can create vortices in the intergalactic medium, around which weak magnetic fields are hooked, bent, and ultimately stretched into filaments with strong magnetic fields.

This is not yet a definitive answer. We don’t even know for sure if the same mechanism is responsible for both types of filaments, or if very different phenomena create structures that look eerily similar.

“All of these filaments outside of our galaxy are very old,” says Yusuf-Zadeh.

“They almost belong to another time in our universe and yet signal to the inhabitants of the Milky Way that there is a common origin for the formation of the filaments. I think that is remarkable.”

The research has been published in Letters from the Astrophysical Journal.

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