Slow-Motion Supernova

Supernovae are generally considered as fast and furious events. For the Type II, core collapse supernovae, the core implodes almost instantaneously although it takes some time for the shockwave to escape the star. As it does, the star brightens in what's known as the "rise time" of the supernova. For most Type II supernovae, this takes about a week.

So what are astronomers to make of supernova 2008iy that had an unprecedented rise time of at least 400 days?

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