Researchers found for the first time that a band of antiprotons have been ringing around Earth, adding to the theory that antimatter could be trapped in Earth’s magnetic field.

The study titled "The Discovery of Geomagnetically Trapped Cosmic-ray Antiprotons," published in Astrophysical Journal Letters, suggests that a thin band of antiprotons has been observed in the Van Allen belt surrounding Earth.

The Van Allen radiation belt is a torus of energetic charged particles around Earth, which is held in place by Earth's magnetic field. It is believed that most of the particles that form the belt come from solar wind, and other particles by cosmic rays.

Piergiorgio Picozza from the University of Rome Tor Vergata, Italy, detected the particles using PAMELA -- a cosmic-ray detector attached to a Russian satellite. PAMELA was launched in 2006 to study the nature of high-energy particles from the Sun and from beyond our solar system.

The big break came from an area known as the South Atlantic Anomaly, which is a region of space where the Van Allen Radiation Belts are the closest to our surface. When PAMELA passes through the South Altantic Anomaly, it finds thousands of times more antiprotons than are supposed to come from normal particle decays or, for that matter, anywhere else.

Between July 2006 and December 2008, PAMELA detected 28 antiprotons trapped in spiraling orbits around the magnetic field lines sprouting from the Earth's South Pole. It doesn't seem to be a big number but that is about a thousand times more than would be expected under normal circumstances.

"We are talking about of billions of particles," Francesco Cafagna from the University of Bari in Italy told "New Scientist" magazine.

The band is "the most abundant source of antiprotons near the Earth", Alessandro Bruno of the University of Bari, a co-author of the study, told the BBC.

The discovery could help mankind to explore the stars, with some researchers believing that the belt of antimatter could be used as a source of fuel -- an idea already being explored by NASA's Institute for Advanced Concepts.