Astronomers discover first '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 'lighting' from a black hole, with variations in brilliance more powerful than ever observed in an extragalactic object. The emission, the researchers suggest in their study, "is associated with pulsar-like particle acceleration by the electric field across a magnetospheric gap at the base of the radio jet."
A galaxy in fake colour: IC 310 image in gamma rays, with enlargement of the central region by the observations of the European VLBI Network EVN. The contour lines and the brilliance show that the jet emerges from the black hole in the heart of IC 310.

The results of 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 Earth. Astronomers believe its centre holds a supermassive black hole. Within this galaxy's centre, 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 Earth and the Sun; that is, 450 millions of kilometres. Light needs 25 minutes to cover that distance', explained Eduardo Ros, researcher from the Max Planck Institute for Radioastronomy and the Universitat de València, co-author of the project.

An object cannot completely change the brilliance of its surface in lees than the time light needs to pierce it. Hence, the region this gamma ray come 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, an unknown opens up to discover what happens in the gravitational tramp that object has had in space.

Pictures in Detail of the Jets

Black holes in the centre of galaxies have a mass of between a million and several billion times our sun's mass. Falling matter towards this objects is 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 radioastronomic 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 València stand out.

IC 310, within the galaxy host of Perseo, belongs to the active-galaxy type In 2009 both the Fermi spatial observatory and the MAGIC telescope detected gamma radiation in 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 energised 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 instrument's quality.

For its part, the director of the Astronomic Observatory of the Universitat de València, José Carlos Guirado, stresses this discovery's importance, 'result of an efficient synergy between instruments working at different longitudes of wave, 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 radioastronomic instrumentation. This is the only way to obtain results like the ones in this week's 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 particleswhen 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 tenured university lecturer, currently working at the Institute Max Planck for Radioastronomy 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 coordination of the cited German institute. Its research field is cantered around the study of galaxies' active nuclei and other compact objects through radioenferometric and astronomic methods of high energies.

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