In 1984, astronomer Farhad Yusef-Zadeh was observing the night sky when he spotted something rather unusual that stopped him in his tracks. He had been working on his PhD at Columbia University, attempting to figure out the nature of compact sources. But along with colleague Don Chance and University of California at Los Angeles professor Mark Morris, he helped identify three large arcs some 150 light years long.
At first they couldn’t believe what they were seeing. Though the existence of filaments had been proposed by Swedish plasma physicist Hannes Alfvén and later proven, nobody other than him thought these one-dimensional strands would stretch to such lengths. Even Yusef-Zadeh, now of Northwestern University in Illinois, wasn’t trying to prove the existence of filaments.
“We were trying to figure out the nature of compact sources in this region,” he says.
But here was a small team staring at potential proof –a discovery made using the Very Large Array (VLA), the world’s most widely used radio telescope, located 80 kilometres (50 miles) west of Socorro, New Mexico. “It was an accident,”
Yusef-Zadeh recalls. “It turned out the compact sources – expected to be HII regions associated with star formation – were peaks of extended filamentary structures. But since this type of structure hadn’t been seen before, we were suspicious that they were real.”
