Decades ago the astronomy world was taken aback by the discovery of strange vertical filaments of light spiking out from our galaxy's central black hole. Now, the astronomer responsible for that finding has spotted more filaments, only these are oriented horizontally and have some other significant – and puzzling – differences.
Farhad Yusef-Zadeh from Northwestern University located the initial filaments in the early 1980s around Sagittarius A*, the supermassive black hole at the center of the Milky Way. Those filaments soar to heights reaching 150 light years and were found all around the black hole.
The newly discovered filaments were found after reducing the noise in images from South Africa's MeerKAT telescope. Not only are they oriented on the same plane as Sagittarius A* rather than perpendicular to it, they are also much shorter, totaling just about five to 10 light-years long. There are also a lot less of them. Additionally, the new filaments seem to be composed of thermal energy, while the vertical filaments are made up of particles moving at the speed of light.
“I was actually stunned when I saw these," Yusef-Zadeh said. "We had to do a lot of work to establish that we weren’t fooling ourselves. It is satisfying when one finds order in the middle of a chaotic field of the nucleus of our galaxy.”
Another key difference is that the horizontal filaments reach towards Sagittarius A* only on one side of the black hole, unlike the vertical filaments. This finding, says Yusef-Zadeh, helps astronomers begin to orient the accretion disk of our black hole as well as its jet-driven outflows. While that's a useful takeaway from the discovery, the true cause of the filaments currently remains unknown.
“We think they must have originated with some kind of outflow from an activity that happened a few million years ago,” Yusef-Zadeh said. “It seems to be the result of an interaction of that outflowing material with objects near it. Our work is never complete. We always need to make new observations and continually challenge our ideas and tighten up our analysis.”
Yusef-Zadeh has been studying the center of our galaxy for decades and, in addition to the filaments, has also spotted a mammoth radio-emitting bubble and an unlikely stellar nursery very close to Sagittarius A*. He says that the MeerKAT telescope, which came online in 2018, has provided radio astronomy with more detailed images than ever before. Such detail helps astronomers like him find previously overlooked structures near our galaxy's black hole.
“The new MeerKAT observations have been a game changer,” he said. “The advancement of technology and dedicated observing time have given us new information. It’s really a technical achievement from radio astronomers.”
The new study has been published in The Astrophysical Journal Letters.
Source: Northwestern University