Astronomers have been left scratching their heads at revelations all galaxies, no matter their size, rotate once every billion years.
On earth, the length of a day is measured against one rotation of the planet on its axis, while the time it takes to orbit the Sun gives us a year.
Lead researcher Gerhardt Meurer said the discovery was "kind of weird."
"I just thought that's kind of odd, small galaxies and big galaxies all orbiting at the same time," Professor Meurer, from the International Centre of Radio Astronomy Research, told AAP.
The WA researchers also found evidence of older stars existing at the edge of galaxies, where only newly formed stars and gas were expected to appear.
"Older theories from the 1960s and 1970s had whole galaxies forming very fast at the earliest part of the universe. That would give you the conditions for a lot of the results we've seen," Prof Meurer said.
"But the old theories, they have been replaced by theories that galaxies form over a longer time, gradually expanding outwards and with older stars closer to the centre of the disc."
He said the discovery would help astronomers understand where galaxies end and no longer waste time, and computer processing power, on data beyond their edges.
The research was published in the Monthly Notices of the Royal Astronomical Society.
