(Inside Science) -- When the Nobel Prize in physiology and medicine was announced today, the official sketch of winner Jeffrey Hall showed the researcher wearing a distinctive hat. A quick image search turned up dozens more photos of him sporting similar head gear. Here at Inside Science, we wondered -- What’s the story behind this striking sartorial choice?

According to Julian Cardillo, a news and communications specialist at Brandeis University in Massachusetts, where Professor Hall performed much of his pioneering research, the Nobel Prize-winning scientist is also a huge Civil War buff, and his hats reflect that passion.

Michael Rosbash, Hall’s fellow Nobel Laureate, said the hats show his colleague’s devotion to the Union effort. “He has tons of them. … There are dress hats, there are officer hats, there are hats for enlisted men, there are hats for parades -- all kinds. But they're all centered on the Civil War and the Union Army,” he said.

According to a profile published in the Proceedings of the National Academy of Sciences, Hall caught the Civil War bug after a family trip to Gettysburg Battlefield in Pennsylvania in 1983, and he delved into the history with a level of dedication similar to what he showed in his scientific work. His enthusiasm was infectious. In 1994, he escorted a group of 250 molecular biologists on a sweeping tour of the battlefield. He even taught a course at Brandeis about the Battle of Gettysburg, and published a textbook on the subject in 2003.

“I have learned a lot about the Civil War through him,” Rosbash said. “He is a true devotee.”

Editor’s Note: Nala Rogers contributed significant reporting to this story. 

For all of Inside Science's coverage of the 2017 Nobel Prizes, go to https://www.insidescience.org/nobel-coverage/2017.

For our coverage of other Nobel Prizes from recent years, please click here.