Ray first checked the data and noticed that when the trigger event was graphed, it showed two peaks instead of one. One peak is what you would expect to see from a nuclear bomb explosion. They then checked data from a satellite that watched the Sun for solar flares. No solar eruptions had been recorded for July 2. No astronomers had reported observing a supernova on that day either. Ray and Roy checked the data from the Vela 3 satellites for that date and those satellites also recorded an event. Something had happened but everything seemed to point to an unknown source of gamma radiation.
First GRB: Gamma-ray bursts (GRBs) are sudden outbursts of gamma rays from random points on the sky, lasting a few seconds or so. The first GRBs were detected by the Vela satellites, which were associated with the U.S. effort to monitor the Nuclear Test Ban Treaty. The data from these surprising events did not resemble the signature of a nuclear bomb explosion. This graph shows the sudden increase in gamma rays recorded for the first GRB detected by the monitoring satellites in 1967.
Credit: R. Klebesadel, I. Strong & R. Olson (LANL), Vela Project
Ray and Roy decided to file the information away until they looked at more data. By 1972 there were additional data from Vela 5 and 6, a new colleague named Ian Strong, and computers to sift through all the data. The team found 16 gamma-ray bursts (GRBs) that could not be traced to a bomb blast, a solar flare, or a supernova. The GRBs were located randomly all over the sky and appeared to be coming from beyond the solar system. Something in space was giving off powerful explosions of gamma rays.
Ray, Roy, and Ian published a paper about their discovery on June 1, 1973, in The Astrophysical Journal Letters. A few days later Ray presented their findings at a meeting of the American Astronomical Society. Only one journalist approached Ray afterwards – from The National Enquirer. He wanted to know if it was possible that the GRBs came from a nuclear war between extraterrestrial civilizations. Ray answered that the signal didn't look like a nuclear bomb explosion but he couldn't rule out the possibility. You can imagine the headlines in the Enquirer the next day, but for the astronomers, the race to find the sources of these cosmic gamma rays was on. I found it intriguing that a detector built to uncover man's biggest explosions found nature's biggest explosions instead.