[AnalogReigns]

After his death, his remains rested in an unmarked grave beneath the floor of the cathedral in Frombork, on Poland's Baltic coast, the exact location unknown.

If the exact location of his original grave was unknown, then how do they know now they are burying his remains?

[vladimir998]

You wrote:

“If the exact location of his original grave was unknown, then how do they know now they are burying his remains?”

1) They probably knew an approximate location within the cathedral.

2) His grave may have been marked on the inside or some identifying thing buried with him.

[DogByte6RER]

From the complete news report at the Yahoo! News link:

“In a later stage of the investigation, DNA taken from teeth and bones matched that from hairs found in one of his books, leading the scientists to conclude with great probability that they had finally found Copernicus.”

[Moonman62]

Good question. The following is from the article:

At the urging of a local bishop, scientists began searching in 2004 for the astronomer's remains and eventually turned up a skull and bones of a 70-year-old man — the age Copernicus was when he died. A computer reconstruction made by forensic police based on the skull showed a broken nose and other features that resemble a self-portrait of Copernicus.

In a later stage of the investigation, DNA taken from teeth and bones matched that from hairs found in one of his books, leading the scientists to conclude with great probability that they had finally found Copernicus.