THE Australian behind the field of galactic archaeology has been awarded the American Astronomical Society's top prize for a lifetime of achievement.

Ken Freeman changed the course of astronomy when he explained dark matter to the world in a paper in 1970 that revealed what we can see of galaxies - the stars, gas and dust - is only a small fraction of their mass.

The rest is invisible dark matter, said his paper.

Professor Freeman from the Australian National University has now been awarded the prestigious Henry Norris Russell Lectureship for a lifetime of seminal contributions to astronomy.

"Many of my old friends, mentors and colleagues are on the list of past recipients of this prize, and it is a great pleasure to be listed with them," he said in a statement on Thursday.

Prof Freeman won the Prime Minister's Prize for Science last year for his work.

He is a founder of the field of galactic archaeology, or research determining the age and movement of stars in our galaxy by their chemical composition.

It was born out of discussions he began in the 1980s with a post-doctoral fellow, Joss Bland-Hawthorn, who is now a professor at University of Sydney.

Most stars in galaxies are formed in groups of between 10,000 and a million stars.

After losing mass they eventually wander off and, after three or four galactic rotations of about 200 million years each, they are spread far and wide throughout the galaxy.

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Aussie professor gets US astronomy gong