Researchers from the University of Warwick state that the astrolabe found in 2014 in the Indian Ocean is the oldest known marine navigation tool.
The astrolabe is an ancient tool used by navigators and astronomers to identify planets and stars, to determine the local latitudes, and to make geographical triangulations.
The relique was excavated by Blue Water Recoveries. Initially, the team was not able to spot any navigational markings on it, so the object was sent to a laboratory in Warwick.
The scanning analyses revealed invisible details using a high-resolution 3D model. The bronze astrolabe measures 17.5 centimeters in diameter and features the Portuguese coat of arms and the personal emblem of D. Manuel I, the King of Portugal from 1495-1521.
"It's a great privilege to find something so rare and historically important; something that will be studied by the archaeological community and fills in a gap," underlines David L. Mearns, the man who led the excavation.
The Portuguese astrolabe was recovered from the wreck of the Esmeralda, a ship that was once captained by the uncle of Portuguese ocean explorer Vasco da Gama, the first to sail directly from Europe to India.
The Esmeralda was making the second voyage to India when it sank in the Indian Ocean in 1503 after a storm. Today, the astrolabe is displayed in the National Museum of the Sultanate of Oman.
Historians and scientists believe that the first astrolabe was developed by Hellenistic civilization, somewhere between 220 BC and 150 BC. However, this instrument continued to be an important tool until the 18th century.