PRAGUE (AP).- Astronomer Tycho Brahe uncovered some of the mysteries of the universe in the 16th century — and now modern-day scientists are delving into the mystery of his sudden death.

On Monday, an international team of scientists opened his tomb in the Church of Our Lady Before Tyn near Prague's Old Town Square, where the famous Dane has been buried since 1601.

Brahe's extraordinarily accurate stellar and planetary observations, which helped lay the foundations of early modern astronomy, are well known and documented but the circumstances surrounding his death at age 54 are murky.

Born in 1546 at his family's ancestral castle, Brahe was in Prague in 1601 at the invitation of the Holy Roman Emperor Rudolph II after having a disagreement with the Danish king and leaving his scientific observatory on the island of Hven.

It had been long thought that Brahe died of a bladder infection — and a famous legend said it was a result of his hesitation to break court etiquette during a reception by leaving for a toilet. Kidney disease was another suspected culprit.

But tests conducted in 1996 in Sweden and later in Denmark on samples of his mustache and hair — obtained during a previous 1901 exhumation — indicated unusually high levels of mercury, leading to a theory of mercury poisoning, even possible murder.

Jens Vellev, a professor of medieval archaeology at Aarhus University, Denmark, is leading the team of scientists from Denmark, the Czech Republic and Sweden. They have until Friday to exhume the remains of Brahe and his wife, who was buried by his side three years later, and will take the necessary samples to the department of archaeology of the Czech National Museum. The results of their analysis will be announced next year.

Brahe's tombstone was lifted from the church's floor Monday by archeologists, then a micro-camera was inserted into the tomb to check its condition. His remains had been in a one-meter (one-yard) long tin box located about 1.6 meters (5 feet, 3 inches) below the church floor.

Vellev said he decided nine years ago to seek permission from church and Prague authorities to open the tomb again because there had been no proper archaeological report on the 1901 exhumation. He also hoped to gather better samples of mustache and hair, and of bones for the first time, that could be analyzed by contemporary technology.

"As a man of science, he's important for the whole world," Vellev said.

He said the tests will include a CT-scan, an X-ray technique known as PIXE analysis and a neutron activation analysis conducted at the Nuclear Research Institute AS in Rez near Prague. Vellev said he thinks the tests will help establish that Brahe's intake of mercury in the last weeks of his life was deadly, possibly from a painkiller that contained mercury.

"Perhaps, we will be able to come close to an answer, but I don't think we will get a final answer," he said, adding that scientists might have to exhume Brahe's remains again in 200 to 300 years to complete his research.

Scientists also are interested in Brahe's skull. The astronomer had part of his nose cut off during a 1566 duel with a fellow nobleman as a student in the German city of Rostock and the missing piece was replaced by a metal plate.

The plate was not found in 1901, but the tests now should be able to determine what it was made of, possibly a silver-copper alloy, Vellev said.

"We are all excited over what will happen in next few days," said the Danish ambassador to Prague, Ole E. Moesby.


Copyright 2010 The Associated Press.