This Baltic coastal village prides itself as the hometown of Nicolaus Copernicus, the astronomer and scientific revolutionary who showed that Earth revolved around the sun. There's a Copernicus museum and a Copernicus altar; even the tower where he did his stargazing almost 500 years ago has been carefully preserved.One thing is missing: Copernicus himself.The people of Frombork have long known that Copernicus died somewhere around here in 1543, but the failure of their ancestors to record exactly where he was buried has fueled one of the most enduring mysteries in Polish history, despite repeated attempts over the centuries to locate his grave.Recently, however, a team of archaeologists reported a breakthrough: the discovery of a skull deep below the flagstones of the 14th-century Frombork Cathedral. Aided by fresh historical research and a high-tech police crime lab, the archaeologists have tentatively concluded that the skull -- that of a man with a broken nose who was approximately 70 years old when he died -- is indeed that of the astronomer.The findings have aroused excitement in Poland, where Copernicus is regarded as a national hero. But they have also forced Poles to make some uncomfortable reckonings with history, such as the question of whether Copernicus was Polish at all.There's also the complicated role in Copernicus's legacy *played by the Roman Catholic Church, which suppressed his research as the work of a heretic for almost 300 years after his death, but is now sponsoring the effort to identify his remains.Historians had long suspected that Copernicus was buried in the Gothic cathedral on a hilltop overlooking Frombork, where he worked as a canon for decades while dabbling in astronomy on the side. But the task of determining exactly where was made all the more difficult because Swedish invaders repeatedly ransacked the crypts beneath the cathedral in the 17th century. Dozens of long-deceased Fromborkians were buried and re-buried on top of each other, turning the church foundation into a giant boneyard.Jerzy Gassowski, the archaeologist who led the search for Copernicus, said he almost turned down the assignment when he was asked by church officials in 2004 to help. "I said, 'No -- that would be like trying to find a needle in a haystack,' " said Gassowski, chairman of the Institute of Anthropology and Archaeology at the Pultusk School of the Humanities, near Warsaw. "I did not believe for one minute that we would discover him."