⚡ Black holes, overloaded with work, must choose between two tasks

Black holes are often described in popular literature as cosmic entities that devour everything in their path, yet they have their limitations.

Scientists have recently observed that active black holes switch between two distinct emission regimes. The projection of a very high-speed plasma jet coincides with a weakening of solar wind and X-ray emissions, and vice versa. This oscillation evokes the motion of a cosmic seesaw, indicating that these objects cannot carry out all their actions simultaneously.


The system 4U 1630-472 was the subject of this study. In this system, a black hole of about ten solar masses captures matter from a companion star. Thanks to NASA's NICER instrument, installed on the International Space Station (ISS), and the MeerKAT radio telescope, the team was able to monitor this phenomenon for three years. This work confirmed that the accretion disk, formed by the stripped matter, remains stable, while the emissions show fluctuations.

Although the stolen matter forms a swirling disk around the black hole, part of it is expelled, either as wind or as a jet. Researchers observed that these two types of emission never occur simultaneously, a sign of competition for the same resource. For the scientists, this highlights an internal mechanism where jets and winds compete for the available energy, thereby altering the system's dynamics.

Despite this alternation, the total amount of energy and mass ejected remains at a constant level. This constancy suggests a self-regulating mechanism by which the black hole maintains a balance in its emissions, likely under the influence of the arrangement of magnetic fields within the disk. According to the study's authors, it is not the volume of absorbed matter that determines the switch, but rather the configuration of these fields.

This regulation has repercussions on the galactic environment. Given that the expelled gas and dust serve as the raw materials for the genesis of new stars, the alternation between jets and winds is likely to affect star formation and, by extension, shape the evolution of galaxies. Black holes thus act as regulators, redistributing part of the matter into their surroundings.

Magnetic fields in black holes

Within the accretion disk surrounding a black hole, magnetic fields emerge from the turbulent motions of heated plasma. Their intensity can become considerable and they directly influence how matter is ejected. These fields act as guides, directing energy either towards the jets or towards the winds detected by astronomers.

A particular configuration of the magnetic fields can favor the emission of high-speed plasma jets. Conversely, another arrangement favors the expulsion of matter in the form of cosmic winds and X-rays. This duality explains why a black hole does not generate both types of emissions at the same time, with the magnetic fields competing to capture the available energy.

Observations of the system 4U 1630-472 show that the alternation between jets and winds is linked to the reorganization of magnetic fields in the disk. This phenomenon does not depend on the amount of matter absorbed, but rather on the internal evolution of the system. Studying these processes helps map how magnetic fields govern black hole activity.