Science and Exploration

Astronomers Discover First Flashes of Lightning from a Black Hole

By Keith Cowing
Press Release
November 11, 2014
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Astronomers Discover First Flashes of Lightning from a Black Hole
Lightning from a Black Hole

An international group of researchers with the participation of the Astronomic Observatory of the Universitat de València has discovered the first lightning bolts from a black hole by eruption with the strongest brightness variations in an extragalactic object ever observed.

In an astronomic sense, we are dealing with flashes with duration of only five minutes. The outcomes of the research on this incredibly strong gamma ray phenomenon in the IC 310 galaxy were published in Science.

The IC 310 radio galaxy in the Perseus constellation is 260 million light-years away from the Earth. Astronomers believe its center holds a supermassive black hole. Within this galaxy’s center, a strong gamma ray eruption was produced; it was detected by the telescope MAGIC at La Palma Island, with complementary images from the European VLBI Network (EVN).

Researchers noted with surprise variations in the radiation coming from the IC 310 galaxy on five-minute time scales. “The event horizon of the black hole — the surface space-time from which nothing can escape the black hole, not even light — is three times higher than the distance between the Earth and the Sun; that is, 450 millions of kilometers. Light needs 25 minutes to cover that distance,” explained Eduardo Ros, researcher from the Max Planck Institute for Radio Astronomy and the Universitat de Valencia, co-author of the project.

An object cannot completely change the brilliance of its surface in less than the time light needs to pierce it. Hence, the region this gamma ray comes from has to be lower, even more than the event horizon in the black hole, according to the researchers. This implies that astronomers have managed to observe the IC 310 galaxy even in more detail than the size of the central black hole. Additionally, there is to discover what happens in the gravitational trap that the object has created in space.

Black holes in the center of galaxies have a mass of between a million and several billion times our Sun’s mass. Falling matter towards these objects are able of producing enormous light flashes in all ranges of the electromagnetic spectrum. These active nuclei in the galaxy produce the so-called jets, in which matter is expelled at a speed close to light’s, which shoots towards outer space of the galaxy. Using radio-astronomic methods it is possible to obtain images of these jets with a unique detail in astrophysics, a research area in which the Department of Astronomy and Astrophysics and the Astronomic Observatory of the Universitat de Valencia excels.

IC 310, within the galaxy host of Perseus, belongs to the active-galaxy type. In 2009 both the Fermi spatial observatory and the MAGIC telescope detected gamma radiation from this object. And to the question of how is it possible that such fast brilliance variations take place, astronomers suggest that the black hole in IC 310’s nucleus is in a fast rotation and surrounded by a strong magnetic camp and “we believe that in the black hole’s polar regions there are huge electric fields, which are able to accelerate fundamental particles at relativist speeds, in a way that when they interact with others of lower energy, are able to produce highly energized gamma rays,” argues Ros. He also adds: “We can imagine this process as a fierce electrical thunderstorm.”

In fact, every few minutes an electrical discharge is produced and affects regions of our solar system. Hence, it is possible for the particles to shoot at speeds close to that of light, within the jet, where they will be accelerated, stopped, reaccelerated and finally centrifuged over the limits of the galaxy itself.

Ros mentions that if black holes are observed both at high energies (gamma rays) and at interferometry VLBI networks, “we are able to obtain unique information on the regions close to the black hole. MAGIC’s and EVN’s observations point towards the mechanisms that form jets in the immediate environment of the black holes; this discovery have been possible thanks to both instruments’ quality.”

The director of the Astronomic Observatory of the Universitat de Valencia, Jose Carlos Guirado, stresses this discovery’s importance, “result of an efficient synergy between instruments working at different wavelengths, gamma rays (MAGIC) and radio waves (Europe’s VLBI network).” Likewise, he highlights, “the presence of astronomers from the UV within this publication which reflects a great continuous effort of a good number of experts from the Astronomic Observatory in research around black holes both from a theoretical field and an observational one and, which are frequent users of this frontline radio-astronomic instrumentation. This is the only way to obtain results like the ones in Science.”

The European VLBI Network EVN is a collaboration of several European, Chinese, South African, Puerto Rican and other country’s radio telescopes, among which we could mention the one in Yebes, Guadalajara and the one in Effelsberg, near Bonn. The telescope MAGIC is located in the Roque de los Muchachos at La Palma and consists of two 17-diameter-meter telescope able to receive cosmic gamma rays at energies between 25 giga-electron-volts and 50 tera-electron-volts. These gamma rays produce avalanches of particles when entering the atmosphere and generate a bluish light called Cherenkov radiation, through which MAGIC can study objects both in our galaxies and in further ones, in this case IC 310.

Eduardo Ross is a UV’s university lecturer, currently working at the Institute Max Planck for Radio Astronomy in Bonn, Germany, in virtue of an agreement between the two institutions. He has been director of the Astronomic Observatory of the Universitat and scientific coordinator of the cited German institute. His research field is centered on the study of galaxies’ active nuclei and other compact objects through radio-interferometric and astronomic methods of high energies.

Lauren Kelly Wickman
+34 961 625 478

“Black hole lightning due to particle acceleration at subhorizon scales,” Aleksic et al., Science, 7 November 2014 [].



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