Jets fired by feeding supermassive black holes at the hearts of active galaxies can be blinked and bent by a “wobble” caused by another orbiting supermassive black hole, a new study reports.
This discovery could help astronomers search for the binary supermassive black hole, which, despite its gigantic nature, remains a needle in a cosmic haystack.
Active galactic nuclei (AGNs) powered by feeding supermassive black holes are often so bright that they can outshine every star in their surrounding galaxy combined. When jets of AGNs are directed directly toward Earth, these events in the cores of galaxies are called blazars.
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These AGNs often glow, and light up briefly. Years of observations of blazars jets show that they are not as straight as one might expect, but rather zigzags and curves. These two phenomena are associated with large amounts of material from the accretion disk of gas and dust surrounding the black hole, which suddenly makes its way into the core and is ejected by jets or fed into the black hole.
The new findings suggest that this could be a very simple explanation, rather than hypothesizing that the curved jets and the brightness of the AGNs could be caused by something causing the jet to “wobble” or advance. The new study suggests that this wobble could be the result of a second black hole lurking in the hearts of bright galaxies. Alternatively, the vortex jet could be caused by a warp in the accretion disk around a single supermassive black hole.
“We provide evidence and discuss the possibility that it is in fact a forward motion of the jet source, either caused by a binary supermassive black hole at the point of the jet’s foot, or, more likely, by an accretion disk twisted around a single black hole.” “The pinhole is responsible for the observed contrast,” study leader Silke Pritzen, a researcher at the Max Planck Institute for Radio Astronomy in Bonn, Germany, said in a statement.
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The team proposes that the jets from the blazars would be forced to wander by the gravitational influence of the second supermassive black hole as it orbits the main black hole feeding the AGN.
“The physics of accretion disks and jets is rather complex, but their macro kinematics (a branch of mechanics concerned with the movement of objects without regard to the forces behind that motion) can be compared to simple gyroscopes,” says study co-author Michal Zagaczyk, who said in the same statement from Masaryk University in the Czech Republic. “If you exert an external torque on an accretion disk, for example, through a secondary black hole orbiting it, it will move and rotate, and with it the aircraft will also move.”
Zagacek added that something similar happens with the Earth’s rotation axis, which is affected by the moon and sun.
It is normal for swirling jets from AGNs to cause periodic changes in their brightness, something that has already been observed over many years in a number of such black hole-fuelled events.
In 2018, the team applied their model of brightness anisotropy and jet curvature to OJ 287, an active galactic galaxy located 5 billion light-years from Earth that is a candidate host to binary supermassive black holes.
Now, scientists have applied the model to 12 of the brightest AGNs. They found that the curvature of the jets and the brightness of the AGN could indeed be attributed to the presence of a second black hole causing the jets to oscillate.
The team cannot completely rule out factors in the aircraft’s physics, such as shock waves or instabilities in the jets, or even magnetic fields, as the driving force behind the curved jets. However, they say that the jets in question would not be quite tortuous or bright were it not for their wobble.
In addition, the researchers were able to detect additional signs of initiation, albeit smaller in amplitude, in the radio light coming from the jets, which they believe is second-order evidence for their model.
The team’s work could eventually give astronomers a better way to search the universe for supermassive black hole binaries at the hearts of galaxies.
“We still lack sufficient precision to directly investigate the existence of binary supermassive black holes,” Pritzen concluded. “But jet motion seems to provide the best signature for these objects, whose existence is predicted not only by the black hole/AGN community, but also by the gravitational wave/pulsar community, who have recently published evidence of a cosmic gravitational background due to gravitational waves.” emitted by the merger of massive black holes throughout cosmic history.”
The study was published in July in the Astrophysical Journal.