Supernova

When stars die of old age, they blow up. Seven thousand nine hundred thirty seven years ago, a star in Cassiopeia exploded into a great big ball of light.

Seventy-five hundred years later (Four hundred and thirty seven years ago today), Tycho Brahe looked up at Cassiopeia and got the news.

Tycho Brahe was very rich and very strange. He lost part of his nose in a duel when he was 20, so he made himself a new one out of silver and stuck it on with paste. His court jester was a dwarf named Jepp, who sat under the table at dinners. And he had a pet elk - at least, he did until the elk drank too much beer at one of Tycho's parties and fell down the stairs and died. Tycho's own death was iffy - popular legend holds that he got a bladder infection from holding it too long at a party, but he may have been poisoned by Jesuits, or his cousin, or his assistant, or he might have poisoned himself by drinking one too many alchemical potions. And if you're a fan of historical facial hair, the Prague National Museum has his moustache in its collection.

Anyway, it was the olden days before they'd even invented telescopes, so something new showing up in the sky was a big deal. The Aristotelian version of the universe insisted on celestial immutability. Or the fixity of the heavens. Basically, the stars didn't move, and they certainly didn't change. Aristotle was an ancient greek, and now it was the Renaissance, and besides, Aristotle was the same fellow who said that bugs and worms sometimes spontaneously generated out of dew and mud, so the world was ready for a step forward. The next year Tycho published a book about the new star, called De Nova Stella, (the new star). And that's why a star is new when it dies of old age.