Astronomers detect mysterious radio waves that took 8 billion years to reach earth

Astronomers have detected a mysterious burst of radio waves that took 8 billion years to reach earth.
The journal Science says that the burst only lasted a fraction of a second but released as much energy as the sun emits over a 30-year period.
The first cosmic flash of this kind was detected on earth nearly 20 years ago. Since then, hundreds of others have been discovered.