There are ten times as many of these structures than scientists previously thought, and their origin remains a mystery.
Researchers using one of the world’s biggest radio telescope arrays to see into the core of the Milky Way have uncovered hundreds of intriguing strand-like objects never seen before.
Radio filaments are long, thin tendrils that extend out of the galactic center, some stretching up to 150 light-years long, or roughly 40 times the distance between Earth and the closest neighboring star system, Proxima Centauri.
Some filaments come in pairs, whereas others, like harp strings, come in equal-spaced groups. According to two upcoming studies approved to The Astrophysical Journal and The Astrophysical Journal Letters, all of them are brimming with energy, which is presumably created by billions of electrons bouncing across a magnetic field at near-light speed.
While scientists have known for decades that filaments exist near the galactic core, recent high-resolution measurements from the MeerKAT radio observatory in South Africa suggest that there are ten times more of the spindly structures than previously imagined. Researchers may be able to ultimately find out what these filaments are and how they were generated by studying them in mass.
“It’s impossible to draw any solid conclusions about what they are and where they originated from just by looking at a few filaments,” said research lead author Farhad Yusef-Zadeh, a professor of physics and astronomy at Northwestern University in Evanston, Illinois. “Now we can see the broad image, which is a panoramic vista packed with a plethora of filaments… This marks a turning point in our knowledge of these structures.”
Bullets of intergalactic energy
The Milky Way’s core is teeming with strange objects that are too shrouded by gas and dust to be studied effectively with visible light wavelengths. Astronomers may see some of the tremendous structures and interactions happening at the galactic core by concentrating on the intense radio waves emanating from there.
The authors of the new study examined the galactic center’s radio activity for 200 hours over three years using the MeerKAT radio telescope, a 64-antenna array in South Africa’s Northern Cape area. The researchers cobbled together a mosaic of 20 unique observations from these data, each concentrating on a different part of the radio sky.
The resultant vista includes the strange fingerprints of roughly 1,000 radio filaments, as well as several recognized sources of radio waves, such as brilliant supernova remnants and the gassy regions of space where young stars are flashing to life.
What precisely are these finger-like structures? The best working idea, according to Yusef-Zadeh, is that the filaments are created by cosmic rays — high-energy particles traveling at almost the speed of light — passing through a magnetic field. Prior research has shown that something hiding at the Milky Way’s core works as a massive particle accelerator, continually shooting cosmic rays outward into space – yet the source of these rays is unknown.
The massive pair of radio bubbles bursting out from the galactic core, one rising slightly above the galactic plane and the other plunging below it, might provide a hint. Each radio energy bubble, discovered in a previous MeerKAT scan, is 25,000 light-years tall (about a fourth of the Milky Way’s diameter) and was most likely created by an old explosion from the galaxy’s core black hole.
Many of the newly discovered radio filaments, according to the authors of the new investigations, are found inside the cavities of these massive bubbles. The strand-like filaments might have been produced by the same ancient burst of black hole activity that inflated the radio bubbles millions of years ago. Even with this explanation, though, certain major concerns remain unresolved.
“We still don’t know why they occur in clusters, how [the filaments] detach, or how these regular spacings arise,” Yusef-Zadeh said. “Every time we answer one question, a slew of new ones pop up.”
The researchers claimed that future radio studies of the area would concentrate on whether the filaments move or change location over time.