When nuclear fusion uses up a star's fuel, in the central high-pressure stellar core where fusion occurs, the star will collapse fairly violently.

CNN: Why gamma-ray burst shocked scientists

Another theory suggests that material surrounding a young star can undergo gravitational collapse under its own mass.

WSJ: Possible New Planet Spotted Under Formation

Theory suggests that a certain type of giant, short-lived star can experience catastrophic collapse when the nuclear reactions at its core can no longer support its mass.

BBC: Telescope spies cataclysmic blast

It was that pulsars are rotating neutron stars, the super-dense last stage of collapse of a star not quite heavy enough to form a black hole.

ECONOMIST: Obituary

That's why an event such as GRB130427A probably signals the collapse of a massive star into a black hole.

CNN: Why gamma-ray burst shocked scientists

Depending on its initial mass, it might collapse to a compact hot star known as a white dwarf (when the star's mass is less than 1.4 times the mass of our sun) or to a neutron star (for stars 1.4 to about three times the mass of our sun) or to a black hole (for stars more massive than three times the mass of our sun).

CNN: Why gamma-ray burst shocked scientists

The band reunited in the mid-1990s after the collapse of the Soviet Union, and its star began to rise.

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These molecules appear at the fringe of the cloud of gas whose gravitational collapse and subsequent heating signals the birth of a star.

ECONOMIST: Planetary formation