Sunshine (2007)

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The Sun is being destroyed from inside out by a type of highly stable form of matter that renders nuclear fusion impossible, by turning common matter on its own kind. The only hope is to send a team of astronauts to detonate a massive, highly energetic bomb, able to destroy this strange matter and restore Sun's natural state. Written by Anonymous

http://www.imdb.com/title/tt0448134/plotsummary