Gamma ray burst

Gamma-ray bursts (GRBs) are the most luminous physical phenomena in the universe known to the field of astronomy. They consist of flashes of gamma rays that last from seconds to hours, the longer ones being followed by several days of X-ray afterglow. These flashes occur at apparently random positions in the sky several times each day.

Related Topics:
Astronomy - Gamma ray - X-ray

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The hypothetical objects that produce gamma-ray bursts are called gamma-ray bursters. There are two types of these bursters, long-duration bursters and short duration bursters. As of summer 2003 the most promising model for the long-duration bursters is that the energy burst is associated with a hypernova event. The death of supermassive stars is brought about by the formation of a black hole at the core, and when this happens a gamma-ray burst occurs. The angular momentum of the star causes the collapsing object to form a spinning torus around the black hole (rather like water spiralling round a plug-hole). There is no infalling matter along the rotation axis, so the gravitational rest mass energy is released in two jets along the rotation axes. If Earth happens to lie along the rotation axis, it receives a huge burst of gamma-rays.

Related Topics:
2003 - Hypernova - Star - Black hole - Gravitational rest mass energy

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The most promising model for the short duration bursts is that developed by Martin Rees in the 1990s. In this model two neutron stars coalese or a neutron star is torn apart by a black hole. This causes an enormous release of gravitational rest mass energy. The lack of material around such a system means that the energy release stops as soon as the merger is complete (hence the short duration of the burst).

Related Topics:
Martin Rees - 1990 - Gravitational rest mass energy

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