It was never mentioned how Tycho died:

He was a heavy drinker, and by the time of his death, had developed a bladder problem.

In the culture of his time, it was considered an insult to leave the table before a meal was over.

He may also not have realised he had this condition, medicine being what it was in the 16th century.

Tycho was invited to a meal at the court of some noble. He neglected to relieve himself before going, and drank too much at dinner besides. The strain within caused his bladder to rupture. It took him eleven days to die.

Also, one of my physics professors told me that Tycho is always referred to by his first name, defying the usual tradition. He never explained why, however.

I'd appreciate a /msg or a writeup that did, though.