Black holes are notoriously ravenous objects, chowing down on anything that comes too close, including light itself. But not everything gets sucked in – many black holes have been found to spew jets of high-speed particles. Those usually form long, straight beams but now astronomers have discovered a weird black hole that's spinning like a wonky top, firing off "bullets" of plasma in all directions.
The object in question is part of a binary system called V404 Cygni, located about 8,000 light-years from Earth. There, a black hole and a star a little smaller than the Sun are locked in a close orbit around each other. The black hole is gradually stripping material away from its partner star, which occasionally creates bright bursts of light. That's how the object was originally discovered in 1989, and attracted attention again with an outburst in 2015.
But when telescopes all around the world were aimed at V404 Cygni, they noticed that the black hole was doing some strange things. Most of the time, if a black hole has jets they fire off from the poles of the object, perpendicular to the cloud of dust and gas that's feeding them material. But the jets on this black hole were flailing around wildly.
"During the outburst we observed details of the jet emissions when material is ejected at a very high speed from the vicinity of the black hole," says Simone Migliari, co-author of the study. "We can see the jets shooting out in different directions on a timescale of less than an hour, which means that the inner regions of the system are rotating quite fast."
For the new study, the researchers examined the center of the system to see what was going on. They used the Integral observatory to watch x-ray emissions from the object for four weeks straight, and the Very Long Baseline Array to study the jets in radio waves.
The team found an abrupt increase in x-ray emissions during the 2015 outburst, which suggests that more material from the surrounding disc was falling into the black hole at that time. That explains the flare-up – but why are the jets moving so erratically?
The researchers used that data to estimate the energy and geometry of the disc material falling onto the black hole, and concluded that the inner part of the disc is on a tilt.
"What's different in V404 Cygni is that we think the disc of material and the black hole are misaligned," says James Miller-Jones, lead author of the new paper. "This appears to be causing the inner part of the disc to wobble like a spinning top that is slowing down, and fire jets out in different directions as it changes orientation."
The scientists aren't sure exactly what could have caused this misalignment, but one suggestion is that the supernova that created the black hole in the first place might have "kicked" it over.
The research was published in the journal Nature. An animation of the V404 Cygni system can be seen in the video below.
Source: ESA
