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Science 1 December 2006:
Vol. 314. no. 5804, p. 1349
DOI: 10.1126/science.314.5804.1349a
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This Week in Science

Figure 1 Among the very few known extragalactic emitters of very high energy tera-electron volt (TeV) gamma rays are blazars, which are galaxies with relativistic particle jets that point toward Earth. It has been suggested that the TeV gamma rays originate in those jets. By monitoring the nearby radio galaxy M87, whose twin jets are oriented in the plane of the sky rather than pointed at us, Aharonian et al. (p. 1424, published online 26 October; see the Perspective by Fabian) show that gamma rays in active galaxies are actually produced near the central black hole. M87 is bright in gamma rays up to 10 TeV, and its brightness varies daily. Such fast variations imply the source of the gamma rays lies near the Schwarzschild radius of the supermassive black hole that lies at the heart of the M87 galaxy. Although this behavior may fit some leptonic models for gamma-ray production, an alternative mechanism of proton curvature radiation near to the black hole is proposed.

CREDIT: AHARONIAN ET AL.




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Science. ISSN 0036-8075 (print), 1095-9203 (online)