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How bright can a supernova become compared with its home galaxy?
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Supernova
Composite image of Kepler's Nova, or Kepler's Supernova, taken by the Chandra X-ray Observatory.
A supernova is a cataclysmic stellar explosion that results in a dramatic increase in luminosity, often becoming millions of times brighter than the star's normal state. During the peak of this eruption, the exploding star releases such a tremendous burst of energy that it can outshine its entire home galaxy.1
To put this energy release into perspective, at the brightest phase of the explosion, the expanding cloud of debris radiates as much energy in a single day as the Sun has produced over the past three million years.2