The universe’s black holes are potent reactors. They provide quasars and other active galactic nuclei with energy (AGNs). This results from the interaction between matter and the powerful gravitational and magnetic forces that it generates.
Although a black hole theoretically has no magnetic field, the dense plasma that surrounds it as an accretion disc does. The charged particles that make up plasma spiral around a black hole produce an electrical current and magnetic field.
Since the plasma flow does not change direction on its own, the magnetic field is probably quite stable. Imagine the researchers’ shock when they found proof that a black hole’s magnetic field had undergone a magnetic reversal.
A magnetic field may be conceptualized as a magnet with a north and south pole. A magnetic reversal occurs when the direction of the imaginary pole and the magnetic field both reverse. This occurrence is prevalent among stars.
The Sun reverses its magnetic field every 11 years, which produces the 11-year cycle of sunspots recorded by scientists since the 1600s. Even the Earth experiences magnetic reversals every few hundred thousand years. However, magnetic reversals were not considered to be probable for supermassive black holes.
In 2018, an automated sky scan detected an abrupt alteration in a galaxy 239 million light-years distant. The galaxy known as 1ES 1927+654 has become 100 times brighter in visible light.
Swift Observatory caught its x-ray and ultraviolet light emission shortly after its detection. An examination of the region’s archival data revealed that the galaxy began to brighten near the end of 2017.
At the time, it was thought that a star passing by the galaxy’s supermassive black hole was what caused this abrupt brightening. A tidal disruption event from such a close collision would shatter the star and obstruct the gas flow to the black hole’s accretion disc. Recent study, nevertheless, casts doubt on this theory.
The researchers looked at data from the cosmic flare across the entire light spectrum, from radio to x-ray. One of the things they observed was a sharp decline in x-ray intensity. This indicated a sudden change in the magnetic field surrounding the black hole, which is normally caused by charged particles spinning under strong magnetic fields.
Simultaneously, the visible and ultraviolet light intensities rose, indicating that portions of the black hole’s accretion disc were heating up. Neither of these outcomes is consistent with a tidal disruption event.
Instead, the findings are best explained by a magnetic reversal. As the researchers demonstrated, when a black hole accretion disc experiences a magnetic reversal, the fields diminish first near the accretion disk’s outer edges.
Consequently, the disc may heat up more effectively. Charged particles create fewer x-rays as a result of the reduced magnetic field. Once the magnetic field’s reversal is complete, the disc returns to its initial condition.
This is the very first detection of the magnetic reversal of a galactic black hole. Now that we know they are possible, we do not know how often these reversals are. It will need further studies to calculate the number of times a galaxy’s black hole may flip positions.
Reference(s): Peer-Reviewed Research Paper
