by Jets that erupt from feeding supermassive black holes at the hearts of active galaxies can light up and spin because of the “wobble” caused by the second spinning black hole, a new study reports.
The revelation could help astronomers hunt for supermassive binary black holes, which, despite their titanic nature, remain a needle in the cosmic haystack.
Active galactic nuclei (AGNs) powered to feed supermassive black holes are often so bright that they can outshine all the stars in the surrounding galaxy combined. When jets from AGN are aimed directly at Earth, these events in the heart of the galaxy are called “blazars.”
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These AGN are often flared, flashing briefly. Years of observations of blazar jets show that they are not as straight as one might expect, instead they often snake and bend. These two events have been associated with large amounts of material from the accretion disk and the dust surrounding the black hole quickly making its way to the center and either ejected by the jet or absorbed into the black hole.
The new results suggest that this may be too simplistic an explanation, instead positing that the curved jets and brightness of AGNs may be caused by something that causes the jet to “move” or pass. This motion may be the function of a second black hole sitting at the heart of a blazar galaxy, a new study suggests. Alternatively, the rotating jet may be caused by a warp in the accretion disk around the supermassive black hole.
“We present the evidence and discuss the possibility that, in fact, the jet source tracking, either caused by a supermassive black hole in the jet area or – under the accretion disk surrounding another black hole, is responsible for the observed variation,” study leader Silke Britzen, researcher at the Max Planck Institute of Radio Astronomy in Bonn, Germany, in a report.
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The jets from the blazars, the team suggests, will be forced into orbit by the gravitational influence of the second supermassive black hole as it orbits the AGN’s main black hole.
“The physics of accretion disks and jets is very complex, but their kinematics (the branch of mechanics that deals with the movement of objects without considering the forces behind that action) can be compared to simple gyroscopes,” study author Michal Zajaček, from the University of Masaryk in the Czech Republic, said. in this report. “If you apply an external torque to the accretion disk, for example, with a second rotating black hole, it will start and nutate, and with it the jet will form.”
The same thing happens with the earth’s rotation axis, which is affected by the moon and the sun, Zajaček added.
The rotation of jets from AGNs will naturally lead to periodic changes in their brightness, something that has been observed over the years in a number of these dark energy events.
In 2018, the team applied their model of light variation and jet bending to OJ 287, an AGN located 5 billion light-years from Earth that is a candidate for hosting supermassive black holes.
Now, scientists have applied the model to 12 bright AGNs. They found that the jet curvature and the brightness of the AGN can actually follow the second black hole causing the jet to vibrate.
The team cannot fully control factors in jet physics, such as shock waves or jet instabilities, or magnetism, such as the driving force behind curved jets. However, they argue, the jets in question would not be as curved or as bright if it were not for their motion.
In addition, the researchers were able to detect additional signs of precession, although smaller in amplitude, in the radio light from the jets, which they consider to be the second proof of their model.
The team’s work could finally give astronomers a better way to search for the universe in the supermassive black hole at the hearts of galaxies.
“We still have enough resolution to probe the existence of supermassive black holes,” concluded Britzen. “But the jet precession seems to provide the best signature of these objects, its presence is expected not only by the black hole / AGN community but also by the gravitational wave / pulsar community, which recently published evidence that there is an origin of cosmic gravitation due to the gravitational waves emitted it is the merger of the largest black holes in the history of the universe.”
The study was published in July in the Astrophysical Journal.
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