Astronomers may have discovered the source of the cryptic 'Wow!' radio message from space, which some believe came from an alien world.
The signal, a 72-second radio burst 20 times brighter than its background emissions, was initially observed in 1977.
Halting at just over a minute because the Big Ear radio telescope could only watch it for that long.
The signal would have likely lasted longer, according to scientists.
Astronomer Jerry R. Ehman drew attention to the unusual transmission on a printout by circling it and writing 'Wow!' next to it.
Although it has never been heard afterwards, it has become a focal point in the quest for extraterrestrial life.