Black hole might have executed a magnetic ‘flip’
A black hole may have reversed its magnetic field right before our eyes. A galaxy known as 1ES 1927+654 briefly ceased X-ray emissions for a few months, then resumed and increased. So far the potential black hole observations represent a unique situation visible from 236 million light years away. If scientists can confirm that the outburst was due to a supermassive black hole at the heart of the galaxy changing its magnetic field, the event may help astrophysicists understand how such a switch affects the black hole’s environment.
The Milky Way and most other large galaxies like it have a supermassive black hole embedded at their heart; the black hole pulls matter in towards its centre. The matter first collects in an accretion disc surrounding the black hole, then heats up and emits light as the matter is pushed inward. As that matter pushes inward, it forms a cloud of extremely hot particles that scientists call a corona. A new study suggests that changes in the corona are what caused the X-rays streaming from the heart of 1ES 1927+654 to temporarily disappear.
If a magnetic reversal took place, causing the north pole to become the south pole, and vice versa, visible and ultraviolet light should increase towards the centre of the galaxy due to more heating as the corona begins to diminish and the accretion disc grows more compact in the centre. But as the flip evolves, the field weakens so much that the corona cannot be supported at all any more, causing the X-ray emissions to cease. That idea matches observations of this galaxy, as X-ray emissions re-emerged in October 2018, roughly four months after they disappeared, suggesting a magnetic reversal took place.