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V407 Cygni

The symbiotic nova V407 Cyg made news headlines in mid-2010 when the Fermi Gamma-Ray Satellite unexpectedly detected gamma rays from its most recent outburst.  The nova was discovered in March of 2010, and has been followed by astronomers world-wide since then.  Surprisingly, the Fermi satellite also found gamma rays, causing a stir in the astronomical community.  Novae originate from white dwarfs that accrete matter from a nearby companion.  This matter collects over time, and when it gets hot and dense enough on the white dwarf's surface, it can undergo thermonuclear fusion.  Such an event can certainly create a lot of light and heat, and even generates X-rays in the process.  But the creation of super-energetic gamma-ray radiation is much harder to do.  A team of scientists led by C.C. Cheung of the United States' Naval Research Laboratory explain the gamma rays as being caused by the interaction of the expanding nova shell with circumstellar material from the secondary star, generating gamma rays through particle collisions and decays.  Their theory isn't proven, but their discovery certainly introduces an interesting new wrinkle into the study of novae.

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