Astronomers have been observing a pulsar with a strange halo. The pulsar is called Geminga and is one the nearest ones to earth. The halo is due to the bright gamma rays in the pulsar. Astronomers believe that Geminga could be responsible for the abundance of only one type of cosmic particle near the Earth . This is the positron which is an antimatter of the electron. This mystery has puzzled scientists for decades. Astronomers used the High-Altitude Water Cherenkov Gamma-ray Observatory to observe Geminga and its halo and concluded that the reachability of high-energy positrons to  Earth entirely depends on the size of the halo.