The Aftermath of Supernova 1987a

A little over 24 years ago, light from the closest supernova in four centuries reached Earth. It was the first such supernova seen in 1987, so it was officially dubbed Supernova 1987A, or SN87A for short.

It was full of surprises: the star that blew up (Sanduleak -69 202) was the first blue supergiant ever seen to explode — most such supernovae progenitors are red supergiants. The intense ultraviolet flash from the explosion lit up a gigantic pre-existing hourglass-shaped shell of gas surrounding the star; over five light years long, nothing quite like it had ever been seen before. The hourglass had a thick ring around its middle, which to this day is still something of a mystery.

The expanding debris from the explosion itself has been growing for more than two decades as well. Screaming out at thousands of kilometers per second, it's been getting less dense as it grows larger, and has been fading as well.

However, that appears to be changing now. The debris is getting brighter once again… which actually has been expected. The gas in the hourglass nebula surrounding the supernova was actually expelled by the star more than 20,000 years ago, and has been sitting there ever since. Inside the dense ring is a thin, hot gas, too faint to be seen directly, but inferred by various means. The debris from the explosion has been plowing into this gas for more than 20 years, but now the expanding material is starting to interact with the ring. Well, to be fair, it's been doing that for a few years, but the real interaction is now starting in earnest.…

See Bad Astronomy for links to further info.

Also see Universe Today and ScienceDaily.com