Although Vermeer himself was proposed as the model of this picture there is no certain evidence of who posed for The Astronomer .To paint oneself on profile with both hands extended it could be difficult to overcome. A more convincing candidate was probably The Delft scientist Anthon Van Leeuwanhoek at the age of 54. He was the inventor of the microscope He was born the same year as Vermeer and he lived a few blocks from him. Whether or not his features are similar is debatable.
However specialists have always believed that the same man with straight nose and full lips, posed for both The Astronomer and The Geographer. None of the models who posed for Vermeer’s interiors have been identified even though many scholars thought that most of them were members of his family, especially his wife and his own daughters.
Essential Vermeer. Available on the Web: http://www.essentialvermeer.com/catalogue/astronomer.html