It's a 21st-century high-tech "whodunit" 400 years after death: did renowned Danish astronomer Tycho Brahe really succumb to kidney failure or was he poisoned, in a royal plot over a love affair?

Pinning their hopes on cutting-edge technologies, a Czech-Danish team on Monday exhumed the nobleman's body from the tomb where he was buried in 1601 inside Our Lady Before Tyn church in Prague's historic Old Town Square.

For four days, they will subject his remains to tests they hope will confirm or deny whether kidney failure will remain the "official" cause of death - or whether something more sinister might have been afoot.

"In fact, we are not coming here to investigate and say it was a murder or not, we're going to investigate... the whole life of Tycho Brahe," said Jens Vellev, a professor from Denmark's Aarhus University who heads the 50-member research team.

It was a test in the 1990s that dealt a blow to the 400-year-old story of Brahe's demise when it showed his beard contained a strong dose of mercury.

The discovery led Danish historian Peter Andersen to maintain that Tycho Brahe - who remains a popular figure in both countries - was poisoned by his distant cousin Eric Brahe in a plot ordered by Danish King Christian IV (1577-1648).

Andersen put forth his theory following the recent discovery of Eric Brahe's diary. He suggests that Christian IV hated Tycho Brahe, an easy-going maverick and bon vivant, because of a love affair he had had with his mother, Queen Sophie.

According to Andersen, Eric Brahe travelled to Prague in April 1601 and quickly won over his cousin's confidence. In October, he supposedly slipped mercury into Tycho's glass, and the astronomer died in agony.

"For the Danish, this is a matter close to their hearts," said Stepan Filipec, pastor at the monumental Gothic church whose two spires dominate the Old Town Square, popular with tourists.

Tycho Brahe, born Tyge Ottesen Brahe in Denmark in 1546, moved to Prague in 1599 after a conflict with Christian IV.

At the time, Prague was a flourishing imperial city attracting the best scientists and artists thanks to the generosity of the Hapsburg emperor Rudolph II. The eccentric monarch thought highly of Tycho Brahe, who used the nickname "The Man With The Golden Nose" for a prosthesis he wore after losing his nose in a duel.

The Dane had discovered a supernova in the Cassiopeia constellation in 1572, and pioneered the geo-heliocentric model in which the moon and Sun both revolve around the Earth while the other planets orbit the sun.

Brahe's erroneous theory contradicted that of the Polish-born father of modern astronomy, Nicholas Copernicus, who decades earlier developed the heliocentric theory that puts the Sun, rather than Earth, at the centre of the universe.

Even if poisoning is confirmed, Eric Brahe is not the only suspect. After the astronomer's demise, rumour had it that his noted German rival Johannes Kepler was very eager to lay hands on the results of Brahe's observations.

Historians, meanwhile, say all may have been Brahe's own fault if he accidentally exposed himself to a harmful substance while conducting experiments.

"History teaches us that mercury was used to treat various diseases," said Jaroslav Podliska, head of the department of archaeology at the National Heritage Institute in Prague.

"Personally, I think he took mercury because he had pain and he took too much and then he died," said Vellev.

Martin Solc from the Faculty of Mathematics and Physics at Charles University in Prague, on the team that tested Brahe's beard in the 1990s, said a salve used to embalm the corpse may have contained the liquid metal.

This week's testing will include a computed tomography scan, a radiographic analysis and other sophisticated examinations, and official results are to be announced some time next year.

If poisoning is confirmed, Czechs may have to rethink an oft-heard expression used here. As the story goes, Brahe died after his bladder burst during a banquet at court, because etiquette forbade him from leaving the table before the emperor.

Today, when Czechs need to leave the table to go to the toilet, the polite refrain is: "Excuse me, please. I don't want to end up like Tycho Brahe."