Key Highlights :
We’ve known for decades that the centre of our galaxy is home to a mysterious phenomenon: a rainbowesque melange of one-dimensional structures hidden in plain sight. Now, a team of scientists has discovered a new population of these filaments, stretching out parallel to the galactic plane surrounding the supermassive black hole at the galaxy’s centre.
The filaments measure 5 to 150 light-years in length, and were first discovered in the 1980s by Farhad Yusef-Zadeh, an astrophysicist at Northwestern University. Since then, the known filaments have increased in number; just last year, a team led by Yusef-Zadeh announced the discovery of a thousand more strands, increasing the number of total known filaments tenfold.
The team’s latest discovery changes the known direction of the filaments; previously, known strands were generally perpendicular to the galactic plane, stretched across it like hash marks. The newly discovered filaments are parallel to it and much shorter than the previously known structures.
The horizontal filaments are only on one side of Sagittarius A*, the supermassive black hole at the centre of our galaxy. Sag A* (for short) lies about 26,000 light-years away and is about 4 million times the mass of the Sun.
The tendrils are one-dimensional – basically, extraordinarily long strands of electrons interacting with a magnetic field. The newly discovered strands are about 6 million years old, by the team’s estimation. The particles composing the longer filaments are travelling at nearly the speed of light, and the horizontal ones appear to accelerate thermal material in a molecular cloud. As such, the stubbier horizontal strands seem to emit thermal radiation.
The team believes that the filaments must have originated with some kind of outflow from an activity that happened a few million years ago. By studying them, scientists could learn more about the black hole’s spin and accretion disk orientation.
Black holes have suffered for their name. They are sometimes presumed to be vacant, inert regions – or at least black box regions where our astrophysical understandings break down. But for all their mysteries – from how they form to how they grow – black holes are incredibly dynamic drivers of cosmic shakedowns and interactions. The filaments in and around the Milky Way centre are just one of the curiosities that needs more investigation, but clearly are connected to the black hole holding everything together.