Home > Astronomy, Gamma Ray Bursts, General Astronomy, Stars, Supernovae > Stars Have Found a New Way to Die

Stars Have Found a New Way to Die


Gamma-ray bursts (GRBs) are brief and intense flashes of gamma-ray radiation that can occur randomly from any direction of the sky. They are so powerful that a single such event can be as luminous as all the visible stars in the sky, but just for a few seconds. They were discovered first during the cold war, when the USA were busy verifying the Nuclear Test Ban Treaty, since for those primitive detectors, GRBs had properties akin to those of the atmospheric atomic explosions. Fortunately, our atmosphere is opaque to gamma rays, which has allowed preserving life on the Earth. But this remarkable property has as a counterpart that GRBs can only be detected by instruments on board of spacecrafts such as NASA’s Swift satellite.

Swift localizes GRBs and distributes their coordinates to astronomers all over the world, who can follow up these explosive events using ground-based telescopes. These observations have shown that GRBs are accompanied by fading emissions from ultraviolet to radio wavelengths, the so-called “afterglow”. This afterglow emission is usually produced by synchrotron radiation emitted by charged particles (mostly electrons and positrons) moving in magnetic fields at ultra-relativistic speeds: velocities above 99.9999% of the speed of light (note that differently from the fractious neutrinos from Gran Sasso, these particles are subluminal).

On Christmas Day 2010 a very peculiar GRB occurred, designated GRB101225A according to the date of its discovery, also nicknamed “the Christmas Burst”. It lasted more than half an hour and, in addition to its extraordinary duration (typically GRBs last a few seconds), it promptly attracted scientists’ attention for the fact that the spectrum displayed a thermal contribution (like a classical blackbody) unusually powerful. Indeed, the thermal component was so powerful that it dominates completely the X-ray-to-ultraviolet emission of this object, challenging the long-standing paradigm that GRB afterglows are produced by non-thermal emission processes (like synchrotron).

Full Story: http://astronews.us/2011-12-01-1313.html

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