A mystery of galactic proportions has finally been solved by a crack team of international physicists, led by those at the Australian National University.

Since the early 1970s, astronomers have tried to pinpoint the source of vast deposits of antimatter within the Milky Way galaxy. 

The Milky Way is home to as many as 400 billion stars and 100 billion planets, including our sun and Earth.

New research by ANU shows antimatter particles in the middle of the galaxy may have been created in a supernova explosion caused by the collision of two white dwarf stars millions of years ago.

Researcher Dr Roland Crocker explained that antimatter in the Milky Way gave off a characteristic gamma-ray signal that scientists had been tracking over 40 years.

"The gamma-rays tell us that there is a lot of antimatter being annihilated within the galaxy," Dr Crocker said.

"What hasn't been clear is what sort of process has produced the antimatter."

Ordinary particles such as protons and electrons each have antimatter equivalents with opposite charges.

When a positively charged proton comes into contact with a negatively charged antiproton, both particles are destroyed and a burst of energy of is emitted.

These bursts of energy, in the form of gamma-rays, reveal the presence of antimatter at the centre of the galaxy.

Dr Crocker said a number of theories had been put forward over the years to explain the presence of antimatter in the Milky Way.

"One idea has been that the antimatter comes from processes associated with the presence of dark matter," he said.

"Another idea has been that, right of the centre of the galaxy there is a big black hole, and the antimatter was associated with that.

"What we can now explain is the antimatter comes from collisions between stars in one of the oldest parts of the galaxy."

This discovery, in turn, shed new light on the early processes that shaped the creation of the Milky Way, Dr Crocker added.

The findings were recently published in the prestigious international journal, Nature Astronomy.