Black hole gamma-ray lightning
The Magic telescopes at La Palma (Canary Islands) have recorded the fastest gamma-ray flares seen to date, produced in the vicinity of a super-massive black hole. Scientists —some of them are members of the Institute of Cosmos Sciences— explain this phenomenon by a mechanism similar to that producing lightning in a storm. This result, with an important Spanish contribution, is published today in Science.
The Magic telescopes at La Palma (Canary Islands) have recorded the fastest gamma-ray flares seen to date, produced in the vicinity of a super-massive black hole. Scientists —some of them are members of the Institute of Cosmos Sciences— explain this phenomenon by a mechanism similar to that producing lightning in a storm. This result, with an important Spanish contribution, is published today in Science.
In the night from 12 to 13 November 2012, the MAGIC gamma-ray telescopes, in the Observatorio del Roque de los Muchachos, were observing the Perseus cluster of galaxies (at a distance of about 260 million light-years) when they detected this extraordinary phenomenon coming from one of the galaxies in the cluster, known as IC310. As many other galaxies, IC310 hosts in its center a super-massive black hole of several million times the mass of the Sun, which sporadically produces intense gamma-ray flares. On this occasion, however, the scientists were astonished by the brevity of the flares, lasting only for a few minutes.
The theory of relativity states that no object can emit for a time shorter than it takes light to cross it. We know that the black hole in IC310 has a size of about 20 light-minutes, approximately three times the distance between the Earth and the Sun. This means that the black hole cannot produce a flare shorter than 20 minutes. However, the flares observed in IC310 lasted for less than 5 minutes.
The scientists of the MAGIC collaboration propose a new mechanism, according to which this “gamma-ray storm” is produced in the vacuum regions created close to the black hole magnetic poles. The phenomenon is similar to what happens in an electric storm. The potential difference is so large that it ends up discharging into a lightning. In this case, the discharge reaches the highest energies observed in nature, and produces gamma rays. The black hole appears to be immersed in a storm of colossal proportions.
Besides the University of Barcelona (UB), the Spanish institutions that participate in the MAGIC consortium are the Institute for High Energy Physics (IFAE, Barcelona), the Universitat Autònoma of Barcelona (UAB), the Institute of Space Sciences (CSIC, Barcelona), the Instituto de Astrofísica de Canarias (IAC, La Laguna), the Complutense University of Madrid (UCM) and the Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT, Madrid).
Article reference:
"Black hole lightning due to particle acceleration at subhorizon scales". Science Xpress, November 2014. DOI: 10.1126/science.1256183