Space has not finished revealing all its secrets, its vastness and complexity are so difficult to access. In particular, black holes are difficult for us to penetrate, but this very first observation could well pierce some of their mysteries.
A mysterious galaxy with unique X-ray emissions
The story begins at the end of 2017, in a galaxy far, far away… Located 236 million light-years from our planet, the galaxy 1ES 1927+654 is then plagued by a strange phenomenon: it shines with a visible light brightness 100 times higher than normal. Initially, astronomers explained that the super-massive black hole at the center of the galaxy would have disintegrated a star passed too close to it (like this incredible example). Now that the event, which spanned almost a year, can be studied in its entirety, researchers are leaning towards another explanation, to say the least astounding.
Accepted for publication last month in the journal The Astrophysical Journal, a scientific article traces the stages of the phenomenon. In March 2018, All-Sky Automated Survey for Supernovae (ASAS-SN, or “Assassin”) scientists observe a drastic drop in X-rays emitted from the galaxy 1ES 1927+654while Ultraviolet rays are 12 times more powerful than expected and that other emissions remain at normal levels. In June 2018, no more X-rays are observed. It was a few months later, in October, that X-ray emissions resumed “normally”, i.e. as much as at the end of 2017. It is this pattern of emissions that challenges researchers, because this is the first time that we have observed this type of result for an active galaxyas Dr. Sibasish Laha, researcher at NASA’s Goddart Space Flight Center and co-author of the study, recalls:
Rapid changes in visible light and Ultraviolet have already been observed in a dozen galaxies similar to this one, but this event marks the first time that we have witnessed an X-ray extinction while other wavelengths waves still emit.
A magnetic reversal could explain the return of X-rays
To explain this unique pattern of observations, researchers describe the organization and functioning of an active galaxy. At the center of almost every galaxy, if not all, a massive black hole attracts around itself an enormous number and density of objects, feeding the galaxy. This cluster, which is in the form of an accretion disk, is called Corona. It is a condensation of extremely hot particles from which emanate very high energy X-rays, maintained by the magnetic field of the black hole around which it orbits. If the galaxy completely stopped emitting X-rays for a time and then returned to previous levels, it would be because the black hole’s magnetic field was reversed.. Prof. Mitchell Begelman, a professor in the Department of Astrophysics and Planetary Sciences at Boulder University in Colorado and co-author of the study, agrees:
A magnetic reversal, where the north pole becomes the south pole and vice versa, seems to be the best explanation for these observations. The field initially weakens around the edge of the accretion disk, leading to increased heat and visible light and UV radiation emissions.
While a great deal of knowledge about magnetic fields and black holes has been accumulated, this first observation will allow further progress in our understanding of the universe. Our planet itself has probably already experienced inversions of this type, but another scientific article projects us into this phenomenon in our time.
