The researchers began watching the supernova just hours after it began. Two weeks later, it reached its peak brightness, but they kept watching it, off and on, for another three months, as the light faded away. In the June (current) issue of Astronomy and Astrophysics, the Nearby Supernova Factory is releasing their 32 nights of data on 2011fe. They even made a movie of it.
Nearly all supernovae are explosions caused by super-giant stars exploding. After a super-giant's core stops fusing, it begins to collapse on itself. As more and more mass falls inward, the atoms are forced to fuse together, resulting in a thermonuclear explosion. Think Nagasaki, but instead of something the size of a softball, it's a star 10 to 70 times bigger than our sun.
That's a Type II supernova.
But there are a few oddballs, known as Type Ia supernovae. Type Ias are also fusion explosions, but they're not caused by the sheer enormousness of the exploding star. In fact, Type Ia supernovae are kicked off by tiny white dwarfs.
When big stars die, they go supernova. When small stars die, their outer layers expand into a planetary nebula (which, remember, has nothing to do with planets) and the surviving core collapses into a white dwarf.
White dwarfs are also known as degenerate dwarfs. (No, not Tyrion Lannister.) These are very old, Earth-sized stellar remnants under so much pressure that it's literally impossible to squish them any further without collapsing the atoms into neutrons.
They're also thieves. If another star wanders close enough to a degenerate dwarf, the dwarf will start stealing mass from it. (If two white dwarfs find each other, they collide in what's called a "double-degenerate" system.) The stolen mass leads to fusion explosions on the white dwarf's surface, called novae.
Remember how astronomers give weird names to things? Novae and supernovae really have nothing in common except for fusion. A nova is a fusion explosion on the surface of a star. A supernova is the explosion of a star.