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Astronomers have fingered a prime suspect behind one of the most important phenomena in the universe: Type Ia supernovae. These violent explosions release their light so precisely that researchers can use them to gauge how fast the universe is expanding. But scientists still don’t know what causes these blowouts. Enter V445, a white dwarf star–an older version of our sun–locked in orbit with another sun about 25,000 light-years away. Back in 2000, V445 sucked away enough matter from its partner to trigger an explosion called a nova. Analysis of the blast showed that it contained no hydrogen, an element also missing in Type Ia supernovae, astronomers report 20 November in The Astrophysical Journal. As such, astronomers plan to keep a close eye on “vampire stars” such as V445 from now on. (Image: ESO)