In 2009, French astronomers observed what was thought to be a weak radio signal from an exoplanet five times bigger than the Earth. However, other attempts to trace the signal has failed, leaving this mysterious, alien radio signal unexplained.

Now, scientists from St. Andrews University in Scotland said the signal may have come from the planet's extreme weather, mainly from its huge lightning storms millions of times more powerful than what we have on Earth, as per The National.

This violent weather may be happening in the exoplanet HAT-P-11b, which is around 124 light years away or 729 trillion miles from Earth. Two years ago, scientists detected water molecules on its surface. Now, its extreme weather may be to blame for the electric signal that astronomers have detected years ago, only to disappear without a trace.

The researchers believe that the signal could have only been produced in conditions of 53 "Saturn-strength" lightning bolts, a phenomenon unimaginable on our planet. On that exoplanet, however, it is not completely impossible, as lead researcher Gabriella Hodosan claims.

"Studies conducted by our group have also shown that exoplanets orbiting really close to their host star have very dynamic atmospheres," she said.

Science News reported that lightning on Venus and Jupiter have also been observed, but not on other planets orbiting other stars. The exoplanet HAT-P-11b is too close to its host star to actually see visible light flashes, but an infrared telescope may be able to detect hydrogen cyanide from its electrical discharge.

The team said it is highly unlikely that the radio signal came from an alien trying to communicate with us.

Dubbed Fast Radio Bursts, these radio signals can be caused by different events, from star explosions to black hole formations, as per Huffington Post. They are very mysterious, often appearing instantly and disappearing just as quick, and never to be traced again.

These signals can be very helpful in understanding our universe more.

The study was published in the Monthly Notices of the Royal Astronomical Society.