The puzzle of where the mysterious antimatter at the heart of our galaxy comes from has finally been solved, according to a top Italian space expert.
Giovanni Fabrizio Bignami, head of the Italian Space Agency, collaborated with the international group of scientists which has just published a paper outlining the answer.
He said the cloud of antimatter at the centre of the Milky Way, which scientists have known about for 30 years, appears to derive from 'binary' star systems distributed in the same area.
Binary star systems are ones in which a normal star is gradually being sucked towards a black hole or a neutron star. Neutron stars are stars that have collapsed under their own gravity and become incredibly dense.
''We have taken a big step forwards in understanding the antimatter at the centre of our galaxy,'' he said, noting that the findings were the result of four years of data supplied by the European Space Agency's satellite Integral.
''We used to think that the source of the anti-matter was a single point, like a black hole,'' Bignami said.
The Integral satellite showed that positrons - one of the key components of antimatter - are spread out over a wide area around the centre and that there are more on one side than the other.
''This seemed very strange and it gave us a big clue, putting us on the trail of the possible source of antimatter''.
The group then noticed that the distribution of binary systems in the galaxy matched the distribution of positrons almost perfectly.
The researchers immediately made the connection and concluded that at least half of the antimatter comes from these binaries.
The findings of the international team, led by Georg Weidenspointer of the Max Planck Institute, were published this week in Nature.
The principle they deduced may well be valid elsewhere in the universe but for now there are no instruments powerful enough to let scientists observe other galaxies in enough detail to tell.
Antimatter is made up of three sorts of subatomic particles: positrons, antiprotons and antineutrons. Their equivalents in normal matter are the negatively charged electrons, positively charged protons and neutral neutrons.
When two like particles of matter and antimatter meet they 'annihilate', disappearing in an explosion.
The existence of antimatter was deduced by British physicist Paul Dirac in the 1920s. Later scientists managed to create it in laboratories. Then astronomers found a mysterious cloud of it at the centre of the Milky Way.
Because Dirac's theory is that matter and antimatter are produced in equal amounts from energy, a question that intrigues many is whether other places exist in the universe which are almost entirely antimatter.
