text: The sources of most GRBs are billions of light years away from Earth , implying that the explosions are both extremely energetic ( a typical burst releases as much energy in a few seconds as the Sun will in its entire 10 billion year lifetime ) and extremely rare ( a few per galaxy per million years ) .
simplified: The sources of most GRBs are billions of light years away from Earth . This suggests the explosions are extremely energetic : a typical burst releases as much energy in a few seconds as the Sun will in its entire 10 billion year lifetime .