He is the director of the Cambridge Astronomical Survey Unit and one of the discoverers of the Cetus Dwarf galaxy and the Sagittarius Dwarf Elliptical Galaxy.

[1][2][3][4][5] Irwin is known worldwide for the leading role he plays in processing of digital optical and infra-red survey data.

Currently, his efforts in processing of digital optical and infrared survey data of Vista Data Flow are being used for processing United Kingdom Infrared Telescope data.

[6] In 2012, Royal Astronomical Society awarded Michael Irwin the 2012 Herschel Medal, which recognises investigations of outstanding merit in observational astrophysics.

[3] According to the Minor Planet Center's official discoverer list, Irwin co-discovered 8 minor planets during 1990–1996.