Astrophysicists have observed what appears to be direct evidence of strong magnetic fields around a black hole, supporting a popular theory about the production of plasma-and-radiation jets observed to emanate from these mysterious objects. The evidence comes from seven years of data showing high-energy polarized light radiated from a region near the event horizon of Cygnus X-1, the first black hole ever observed.
Polarized light is light that vibrates in a specific pattern, and it can be a signature of radiation from charged particles that are sped up in a magnetic field. The magnetic field is a product of super-hot plasma — material torn from a nearby star — that’s smeared into a disk around the black hole. The twisting of the magnetic field lines as the black hole rotates is believed to be the mechanism for producing jets.
Cygnus X-1 was discovered as a mysterious X-ray source in the 1960s, but it was many years later when astrophysicists reached consensus that it was a black hole1. The discovery and speculation as to its nature inspired the prog-rock band, Rush, to write a song about Cygnus X-1 in the late 1970s, complete with some of the best rock-song lyrics of all time:
 Consensus unofficially dated to 1990 when physicist Stephen Hawking famously conceded a bet with fellow physicist Kip Thorne that observational evidence supported the theory that Cygnus X-1 was indeed a black hole.