Yes, and researchers at the University of Buffalo say they have found indirect proof of their existence. They studied 355 quasars – very bright galaxies with super massive black holes at their centre (said without batting an eye). Quasars emit massive jets of energy and 183 of such jets were seen to line up to form a pair of enormous rings in the sky, suggesting two massive circular structures actually exist – or did exist. The only known, or theorised feature that could explain such collapsed structures are cosmic strings – which provides compelling indirect evidence for their existence. It is said.