BLACK holes range from modest objects formed when individual stars end their lives to behemoths billions of times more massive that rule the centres of galaxies. A new study using data from the National Aeronautics and Space Administrations (NASA) Swift satellite and the Fermi Gamma-ray Space Telescope shows that high-speed jets launched from active black holes possess fundamental similarities regardless of mass, age or environment. The result provides a tantalising hint that common physical processes are at work. The study has been published in the journal Science.
What were seeing is that once any black hole produces a jet, the same fixed fraction of energy generates the gamma-ray light we observed with Fermi and Swift, said lead researcher Rodrigo Nemmen of NASAs Goddard Space Flight Centre.
Gas falling towards a black hole spirals inward and piles up into an accretion disk, where it becomes compressed and heated. Near the inner edge of the disk, on the threshold of the black holes event horizon, the point of no return, some of the material becomes accelerated and races outward as a pair of jets flowing in opposite directions along the black hole spin axis. These jets contain particles moving at nearly the speed of light, which produce gamma raysthe most extreme form of lightwhen they interact.
At the other end of the scale are gamma-ray bursts (GRBs), the most powerful explosions in the universe. Astronomers believe that the most common type of GRB heralds the death of a massive star and the birth of a stellar-mass black hole. When the stars energy-producing core runs through its store of fuel, it collapses and forms a black hole. As the stars overlying layers cascade inward, an accretion disk forms and the black hole launches a jet. When the jet breaches the stars surface, it produces a pulse of gamma rays typically lasting a few seconds, which, if directed towards the earth, satellites like Swift and Fermi can detect.
To study the properties of these jets across a wide range of masses, the scientists looked at the galactic equivalent of GRB jets, which come from the brightest class of active galaxies: blazars and quasars. To match the amount of energy given off by a typical blazar in one second, the sun must shine for 317,000 years. To equal the energy a run-of-the-mill GRB puts out in one second, the sun would need to shine for another three billion years.
The astronomers examined 54 GRBs and 234 blazars and quasars. The gamma-ray brightness obtained with Fermi, Swift and other observatories told the scientists how much light the jets radiate. Radio and X-ray observations allowed them to determine the power of the particle acceleration in each jet. By analysing how these two properties related to each other, the researchers discovered that the GRB and blazar samples both exhibited the same relationship. The finding simplifies astronomers understanding of black holes by showing that their activity is governed by the same set of rules, whatever they happen to be, independent of mass, age, or the jets brightness and power.
The authors of the work hope to extend the research to other black-hole-powered events that launch jets, such as the tidal disruption of stars by supermassive black holes.
COMMents
COMMents
SHARE