Yes, AUTONOMOUS is a Scrabble word!

Letter values in Scrabble US: A 1, U 1, T 1, O 1, N 1, O 1, M 3, O 1, U 1, S 1.

Is it a valid word?

AUTONOMOUS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

(of political bodies) not controlled by outside forces
existing as an independent entity
(of persons) free from external control and constraint in e.g. action and judgment

Also: self-governing, self-directed, self-reliant.