Now they are found to be produced by thunder storms on Earth, with 1000's of gamma rays detected. The number will increase as we start to investigate the production of the Earth gamma rays.
Surely that will mean a rethink on the science theories that did not predict this?
Scientists have shed light on a mysterious phenomenon that occurs in thunderstorms.
They have discovered that gamma-ray bursts - the most powerful explosions of energy in the Universe - are far more common on Earth than was thought.
Data from Nasa's Fermi satellite shows that all storms produce the blasts and an estimated 1,100 occur each day.
The findings were presented at the American Geophysical Union's Fall Meeting.
Until recently, it was thought that gamma-ray bursts were only found in deep space.
“These are big, monster bursts of gamma rays, and one would think these must be monster storms producing them - but that's not the case”
Prof Joseph Dwyer University of New Hampshire
The pulses of high-energy light are hurled out when giant stars explode or black holes or neutron stars merge.
But in the 1990s, scientists found that these events also occur in the Earth's atmosphere during storms, although it was thought they were rare.
Now, new research has revealed that almost every type of storm - no matter what its strength - produces these invisible explosions.
Gamma-ray bursts 'common in storms'