PRAGUE (Reuters Life!) - Was it accidental poison or murder most foul? Could it have been a sudden illness or the dark result of envy among two of history’s greatest astronomers?

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

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 the 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 analysis 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 who he had fallen out with or that his now more famous assistant Johannes Kepler murdered him to get his hands on Brahe’s astronomic observations.

An illness causing kidney failure is another possibility for a colorful character, who wore a prosthetic nose said to have been made of precious metal to hide the loss of the bridge of his real nose in a duel.

One popular legend says Brahe, also said to have enjoyed a party or two, died after a dinner where his bladder burst because etiquette prevented him from leaving the table attended by the king. Doctors have said that theory doesn’t hold water.

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 told Reuters Television. “But we can perhaps decide if he took so much mercury he could die of it.”