Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. After the explosion , an expanding supernova envelope is observed to brighten over a a period of days to a maximum light output which rivals that of an entire galaxy before fading from view over the following months. Triggered by the collapsing core of a massive star or the nuclear demise of a white dwarf supernovae occur in average spiral galaxies only about once every 25-100 years . But a recent observation of NGC 664, a spiral galaxy about 300 million light years distant, captured a rare and colorful performance - two supernovae from the same galaxy. The color difference is due to temperature - blue is hotter .
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