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Intro music.

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As Swift begins its investigation of gamma-ray bursts,

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NASA scientists are anxious to see if their origins lie in the explanations of three possible theories.

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Ranging from simple to complex, all three theories have something in common:

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the destruction of stars to form infamous black holes.

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The first theory suggests a burst is triggered when a star's core collapses.

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Millions of years before the collapse, the hydrogen fuel inside the core begins to wither.

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Once the internal fuel supply is exhausted, the core implodes and creates a black hole.

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Within seconds of its formation, tandem particle jets erupt from the black hole's center.

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The twin jets rupture the star and produce a supernova explosion.

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This stellar detonation in turn ignites the gamma-ray burst.

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Like the previous "collapsar" theory, the supernova model also involves the implosion of a star's core.

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As the star burns the last of its hydrogen, it swells into a red super-giant.

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At the same time, the inner iron core implodes, compressing its atoms and raising the internal temperature by billions of degrees.

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This rapid increase in temperature and pressure unleashes a devastating shock wave.

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When the shock wave reaches the star's outer layers,

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they are superheated and thrust out into space, resulting in a brilliant release of supernova light.

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The final concept is known as the binary merger theory.

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Perhaps the simplest of all the theories, it begins with a pair of neutron stars,

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or a neutron star and a black hole orbiting each other.

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The gravity between the two objects causes them to draw nearer and whirl at increasing speed.

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The force of their gravitational attraction is so strong that it begins to distort their shape.

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Before long, the two objects merge, producing a black hole and an eruption of gamma rays.

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