Professor Tom Marsh, 60, had been visiting La Silla Observatory on a research trip. He was last spoken to on Friday night (September 16).
Officers from Warwickshire Police are in contact with the Foreign Commonwealth and Development Office (FCDO) and Interpol, as well as Chilean authorities.
Specialist officers are also supporting Professor Marsh’s family.
His family – who live in the Rugby area – said: “We are deeply concerned for Tom and miss him, and would ask anyone who may any have information on his whereabouts to please help.”
Warwickshire Police said: "He is described as white, approximately 6’3” in height, with balding grey hair and a beard. He is likely to be wearing a blue rain jacket, walking boots and a grey woollen hat.
"If anyone has any information, please call Warwickshire Police on 101 quoting incident number 153 of 18 September 2022."