The University of Michigan Library described the document as one of its “great treasures”, believing it to be a draft of a letter sent by Galileo to the Doge of Venice in 1609.

However, a historian at Georgia State University contacted the library to raise his suspicion that it was forged by notorious 20th century counterfeiter Tobia Nicotra.

After its own investigation, the university has agreed that the item is most likely a fake, The New York Times reports.

Donna L. Hayward, interim dean of the library, said: “It was pretty gut-wrenching when we first learned our Galileo was not actually a Galileo.”