Czech and Danish scientists recently opened the Prague tomb of Danish astronomer Tycho Brahe in an attempt to discover what killed the alchemist in 1601. Brahe's observations of celestial bodies laid the foundations for modern astronomy and the fame of his assistant, Johannes Kepler.

Speculation has long centered around three theories. Brahe—who worked at the Prague court of Holy Roman Emperor Rudolph II and is a popular figure in Czech and Danish history—was murdered, became ill or simply ingested too much of a toxic substance, such as mercury, in the course of his experiments.

The Czech Academy of Sciences said nuclear scientists will test bone and hair samples taken from Brahe's remains in Our Lady Before Tyn Church in Prague's medieval Old Town Square. They will be looking for mercury and other substances that could shed light on the cause of his death. Some presence of mercury was shown by earlier analyses of his facial hair.

Scientists said longer-term exposure to poison would indicate Brahe may have died from self-administered "medicine" or too much exposure from his experiments. However, high concentrations of a toxic substance near the hair root could indicate a big one-time dose of poison.

"Generally the finding of high concentrations of a toxic element, such as arsenic, in sequential hair samples of a potential murder victim is considered an indicator of a murder and can be used as evidence," said Jan Kucera from the Nuclear Physics Institute in Rez near Prague. One murder theory says that Brahe was killed on the orders of Danish King Christian IV, with whom he had fallen out, or that his more famous assistant, Johannes Kepler, murdered him to get his hands on Brahe's astronomic observations.

Further tests will be done at universities in Lund, Sweden and Odense, Denmark, the Czech Academy of Sciences said. "It is impossible to say if he was murdered or not," research leader Jens Vellev of Aarhus University said. "But we can perhaps decide if he took so much mercury he could die of it."

Tycho Brahe (14 December 1546–24 October 1601), born Tyge Ottesen Brahe, was a Danish nobleman. Brahe was born at Knutstorp Castle, then part of Denmark, now part of modern-day Sweden, part of the province of Skåne [Scania].