February 5th, 2022
Researchers using one of the world’s largest arrays of radio telescope have found thousands of mysterious strand-like structures while looking into the center of the Milky Way.
These structures, which are also called radio filaments, pop out of the galactic center in long, thin tendrils that expand up to 150 light-years long or nearly 40 times the distance between Earth and the closest next-door star system, Proxima Centauri.
According to two upcoming studies endorsed to the Astrophysical Journal and the Astrophysical Journal Letters, some of the filaments come in pairs or clusters while others appear like the strings of a harp in equally-spaced sets. All of them flare with energy which is likely produced by billions of electrons bouncing through a magnetic field at near-lightspeed.
Although scientists have noted that such filaments exist around the galactic center for many decades, this new set of high-definition observations from the MeerKAT radio telescope in South Africa shows that there are 10 times more of the elongated structures than earlier thought. Studying the strange structures in bulk could assist researchers to completely unravel what these filaments are and how they were created.
“Just examining a few filaments makes it difficult to draw any real conclusion about what they are and where they came from,” said study lead author Farhad Yusef-Zadeh, who is also a professor of physics and astronomy at Northwestern University in Evanston, Illinois.
Center of the Milky Way is crowded with baffling objects
“Now, we finally see the big picture – a panoramic view filled with an abundance of filaments. This is a watershed in furthering our understanding of these structures.”
The center of the Milky Way is crowded with baffling objects that are too covered by gas and dust to properly study with visible light wavelengths. But by focusing on the energetic radio waves radiating from the galactic center, astronomers can catch a glimpse of some of the forceful structures and interactions happening there. (Related news: Milky Way galaxy likely teeming with Earth-like planets, study suggests.)
Using the MeerKAT radio telescope, which is an array of 64 antennas in the Northern Cape province of South Africa, the researchers of the new studies examined the galactic center’s radio activity for 200 hours, stretched over three years. From these investigations, the researchers put together a mosaic of 20 separate observations, each focusing on a distinct section of the radio sky.
MeerKAT, formerly known as the Karoo Array Telescope, is a radio telescope introduced in 2018 and its 64 antennas cover a diameter of eight kilometers.
It is also the most sensitive telescope of its kind and is a forerunner to the Square Kilometer Array radio telescope, which will be constructed in South Africa and Australia within the next decade.
The resulting panorama captures numerous known sources of radio waves such as bright supernova remnants and the gassy regions of space where new stars are sparkling to life, including the mysterious fingerprints of nearly 1,000 radio filaments.
Filaments produced by cosmic rays
According to Yusef-Zadeh, who was the first to find the highly organized, magnetic filaments in the early 1980s, the finger-like filaments are produced by cosmic rays – a form of high-energy radiation that originate from outside the solar system. Previous studies have shown that something hiding at the center of the Milky Way works as a giant particle accelerator, continually firing cosmic rays outward into space even though the source of these rays is still a mystery.
One evidence might be the gigantic pair of radio bubbles blowing out from the galactic center, one rising above the galactic plane and the other descending below it. Found in a prior MeerKAT survey, each bubble of radio energy exceeds roughly 25,000 light-years high and was likely made by an ancient explosion from the central black hole of the galaxy.
Many of the newly detected radio filaments, according to the researchers of the new studies, descend within the cavities of these massive bubbles and it is possible that the strand-like filaments were made by the same ancient burst of black hole activity that bloated the radio bubbles millions of years ago.
“We still don’t know why they come in clusters or understand how [the filaments] separate, and we don’t know how these regular spacings happen,” Yusef-Zadeh said. “Every time we answer one question, multiple other questions arise.”
The researchers added that future radio surveys of the region will concentrate on whether the filaments are moving or changing position over time.