What Causes Gamma-Ray Explosions? Their ultra-bright brightness preserves traces

July 1967, American satellites launched in search of Soviet nuclear weapons at the height of the Cold War I found something completely unexpected. Vela 3 and 4 satellites observed short glows of high-energy photons or gamma rays coming from space. Later in the year 1973 paper who collected more than a dozen such mysterious events, astronomers would have doubled the gamma-ray bursts. “Since then, we’ve tried to understand what those explosions are,” he said Andrew Taylor, German Electron Synchrotron (DESY) physicist in Hamburg.

After the initial discovery, astronomers discussed where these gamma-ray bursts came from — to find out what drives critical light. Some thought that bright sources like this should be close by, in our solar system. Others argued that they are in our galaxy, while others are in the cosmos beyond. Theories were plentiful; no data.

In 1997, an Italian and Dutch satellite called BeppoSAX confirm that the gamma-ray bursts were extragalactic, in some cases millions of light-years away.

This discovery was astonishing. To find out how bright these objects were — even when looking at these distances — astronomers realized that the events that caused them must have been almost unimaginably powerful. “We thought there was no way to get that amount of energy in an explosion from any object in the universe,” said astrophysicist Sylvia Zhu of DESY.

A matter-ray explosion will emit the same amount of energy as a supernova, created when a star falls and explodes, but in seconds or minutes than weeks. Their greatest luminosity could be 100,000 trillion times that of our sun, and a billion times that of the brightest supernovae.

He was lucky that they were so far away. “If a gamma ray exploded in our galaxy with a jet pointed at us, the best thing you could expect is a rapid disappearance,” Zhu said. “You would expect radiation to break through ozone and kill everything immediately. If the worst-case scenario is further away, some of the nitrogen and oxygen in the atmosphere can be converted to nitrous dioxide. The atmosphere would turn brown. Death would be slow. ”

Gamma ray bursts have two flavors, long and short. The first, which can last about a few minutes, is thought to arise from the stars 20 times the mass of our sun falling into black holes and exploding as a supernova. The latter, which last for more than a second, are formed by two joined neutron stars (or perhaps one neutron star joining a black hole). It was confirmed in 2017 Gravitational wave observatories detected neutron star fusion and captured the explosion of gamma rays associated with NASA’s Fermi Gamma ray space telescope.

In each case, the explosion of gamma rays does not come from the explosion itself. The explosion comes from a jet that moves below the speed of light in opposite directions. (The exact mechanism that feeds the jet remains a “very basic question,” Zhu said.)

“This combination of high-energy speed and jet focus makes them very bright,” he said. Nial Tanvir, Astronomer at the University of Leicester in England. “That means we can see them from afar.” On average, it is believed to exist a gamma ray observer exploded in the visible universe every day.

Until recently, the only way to study gamma-ray bursts was to observe them from space, as the Earth’s ozone layer blocks gamma rays from reaching the surface. But when gamma rays enter our atmosphere, they collide with other particles. These particles are propelled faster than the speed of light into the air, which leads Cherenkov to emit a blue glow known as radiation. Scientists can look for these blue bursts of light.