A violent fate awaits a white dwarf star that wanders too close to a moderately massive black hole. According to a new study from the University of California at Santa Cruz, the black hole's gravitational pull on the white dwarf would cause tidal forces sufficient to disrupt the stellar remnant and reignite nuclear burning in it, causing a supernova explosion.

Observations of such supernovae could confirm the existence of intermediate-mass black holes, which are 500 to 1,000 times the mass of the Sun and currently the subject of much debate among astronomers. This new mechanism for ignition of a white dwarf results in the formation of a luminous accretion disk that emits x-rays that should be detectable by the Chandra X-ray Observatory.

Researchers estimated that this type of event would occur about 100 times less frequently than a standard type Ia supernovae, but should be detectable by future surveys designed to observe large numbers of supernovae. The Large Synoptic Survey Telescope (LSST), planned for completion in 2013, is expected to discover hundreds of thousands of type Ia supernovae per year. It is also expected that these exotic supernovae will start showing up in the data from the LSST.

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