Zoom in on gamma eruptions from the black hole of the galaxy M87
By combining the radio telescopes of the VLBA and three instruments working in the field gamma, astronomers have observed more precisely than ever the black hole center of the famous radio galaxies M87. Conclusion: it is in his immediate environment that will produce powerful eruptions gamma. When a black hole is surrounded by a disk of matter spiraling toward its event horizon (surface defining the region of the spacetime occupied by that planet and that not even light can escape) of large amounts of gravitational energy can be converted into bursts of radiation in the radio fields, X and gamma.
In the case of a central black hole in a galaxy, the energy released by
the accretion process becomes monstrous and, coupled with relativistic magnetohydrodynamic process complex due to the rotation of the black hole, it explains the power the active nuclei of galaxies that are quasars.
The radio galaxy M87 is one of the most studied by astronomers and astrophysicists. It is located 55 million light-years around and boasts a powerful jet of material emitted by its central black hole whose mass is estimated at six billion solar masses. It has to be 120 hours of observations conducted using radio telescopes of the Very Long Baseline Array (VLBA) and three other instruments scrutinizing the secrets of the cosmos in gamma rays.
By combining radio telescopes scattered across the globe, it is possible to obtain images at very high resolution as if we had a satellite thousands of miles in diameter. The researchers' goal was to try to locate where exactly in M87 eruptions occurred in gamma, known to be associated with bursts of radio waves for longer periods.
It was of course natural to imagine that these emissions, intense but short of photons of trillions of times more energy than the sun in the visible range should occur in the accretion disk of the Kerr black hole of supermassive M87, or at least throw his high-energy particles.
An artist's representation of the disk of dust and gas spiraling toward a giant black hole in rotation. Two jets of matter particles and photons at different wavelengths are then issued. The black dot in the center of the accretion disk represents the black hole itself. Credit: Bill Saxton, NRAO / AUI / NSF
But the universe defies theories sometimes the most rational and at first the most logical. An audit was needed ... From January to May 2008, the three most sensitive instruments in the field of gamma photons of very high energy, VERITAS, HESS and Magic observed M87 for a total of 120 hours, together with the VLBA.
Two bursts were detected gamma in M87 and, as in the case of the first observations of this kind in 1998, followed by those of 2006, a variability of gamma photon flux for a few days was measured. This implies that the size of the source may itself be a maximum as the magnitude of the distance traveled by light during this period. This was well consistent with the hypothesis that it was in close liaison with the central black hole of this elliptical galaxy that gamma eruptions occur.
Click to enlarge. The VLBA zoom covers the tip of the jet of M87 X already studied by Chandra. Shown at bottom right. The accretion disk and the base of the jet material are clearly visible in radio. Credit: Bill Saxton, NRAO / AUI / NSF
As shown in the images obtained with the extraordinary power of resolution VLBA radio is actually near the black hole that the generation of gamma photons and radio bursts occur. The accuracy is such that Astrophysicists now know that eruptions occur only 50 times the size of the horizon of the supermassive black hole in M87. This is about two times larger than our solar system.
Researchers now believe that gamma-ray flares and radio began with the ejection of a cloud of particles traveling at nearly the speed of light in the jet on M87. As and when the blast of particles is diluted in the jet, the gamma emissions cease fairly quickly but the radio and them, increasing in intensity for at least two months.
An article in Science describes all of the discoveries made by astronomers. Presumably, in the years these instruments will bring new discoveries about phenomena that occur near a black hole. They should complement those resulting from studies, finer, our own central black hole.
The radio galaxy M87 is one of the most studied by astronomers and astrophysicists. It is located 55 million light-years around and boasts a powerful jet of material emitted by its central black hole whose mass is estimated at six billion solar masses. It has to be 120 hours of observations conducted using radio telescopes of the Very Long Baseline Array (VLBA) and three other instruments scrutinizing the secrets of the cosmos in gamma rays.
By combining radio telescopes scattered across the globe, it is possible to obtain images at very high resolution as if we had a satellite thousands of miles in diameter. The researchers' goal was to try to locate where exactly in M87 eruptions occurred in gamma, known to be associated with bursts of radio waves for longer periods.
It was of course natural to imagine that these emissions, intense but short of photons of trillions of times more energy than the sun in the visible range should occur in the accretion disk of the Kerr black hole of supermassive M87, or at least throw his high-energy particles.
An artist's representation of the disk of dust and gas spiraling toward a giant black hole in rotation. Two jets of matter particles and photons at different wavelengths are then issued. The black dot in the center of the accretion disk represents the black hole itself. Credit: Bill Saxton, NRAO / AUI / NSF
But the universe defies theories sometimes the most rational and at first the most logical. An audit was needed ... From January to May 2008, the three most sensitive instruments in the field of gamma photons of very high energy, VERITAS, HESS and Magic observed M87 for a total of 120 hours, together with the VLBA.
Two bursts were detected gamma in M87 and, as in the case of the first observations of this kind in 1998, followed by those of 2006, a variability of gamma photon flux for a few days was measured. This implies that the size of the source may itself be a maximum as the magnitude of the distance traveled by light during this period. This was well consistent with the hypothesis that it was in close liaison with the central black hole of this elliptical galaxy that gamma eruptions occur.
Click to enlarge. The VLBA zoom covers the tip of the jet of M87 X already studied by Chandra. Shown at bottom right. The accretion disk and the base of the jet material are clearly visible in radio. Credit: Bill Saxton, NRAO / AUI / NSF As shown in the images obtained with the extraordinary power of resolution VLBA radio is actually near the black hole that the generation of gamma photons and radio bursts occur. The accuracy is such that Astrophysicists now know that eruptions occur only 50 times the size of the horizon of the supermassive black hole in M87. This is about two times larger than our solar system.
Researchers now believe that gamma-ray flares and radio began with the ejection of a cloud of particles traveling at nearly the speed of light in the jet on M87. As and when the blast of particles is diluted in the jet, the gamma emissions cease fairly quickly but the radio and them, increasing in intensity for at least two months.
An article in Science describes all of the discoveries made by astronomers. Presumably, in the years these instruments will bring new discoveries about phenomena that occur near a black hole. They should complement those resulting from studies, finer, our own central black hole.
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on Feb 10th, 2010 and filed under Astronomy.
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