An international team of astronomers has identified a universal rule governing the production of powerful jets by black holes, finding that these objects launch jets at the same critical stage of their feeding cycle regardless of their size.
The Role of Accretion and Tidal Disruption
Black holes are dense concentrations of matter where gravity is so strong that nothing, including light, can escape once it passes the event horizon, Nasa reports. While they do not suck in matter like vacuum cleaners, they are often surrounded by accretion disks of gas and dust that emit light across various wavelengths.
To study these processes, researchers focused on tidal disruption events, which occur when a black hole tears apart a star. Because these feeding episodes can evolve over just a few years, they provide a faster way for scientists to observe processes that would otherwise take thousands or millions of years to unfold around supermassive black holes.
Two Phases of Jet Formation
Researchers tested their hypothesis by examining 20 tidal disruption events using radio waves, X-rays, ultraviolet light, and optical light. After narrowing the sample to 10 high-quality events, the team identified two distinct periods when jets can form:
- An early phase that occurs while the black hole is consuming material at an extremely high rate.
- A later phase occurring hundreds to thousands of days after the star is torn apart.
The second phase occurs when the feeding rate drops to approximately two percent of the Eddington limit, which is the point where the inward pull of gravity is balanced by the outward pressure of radiation.
The ability to anticipate these eruptions may assist future observatories, such as the Square Kilometre Array radio telescope project, which is expected to start collecting scientific data in 2028. This could lead to more efficient use of heavily requested telescopes by reducing observations during periods of expected inactivity.