Weak radio signals in space could indicate the existence of aliens.
The sounds, which have been detected by the world's most powerful telescope, appear to be from hidden planets.
Astronomers picked up signals from 19 red dwarf stars 165 light years away, with four thought to have planets that could be home to alien life orbiting them.
Scientists believe that the signals are generated by a planet's magnetic fields interacting with the solar wind.
Expert Dr. Benjamin Pope said: "It is the first time radio signals from planets outside our solar system have been picked up.
"This could potentially lead to the discovery of planets throughout the galaxy."
The strange signals were heard by the Dutch-based Low-Frequency Array radio telescope.
Dr. Joseph Callingham, of Leiden University in the Netherlands, added: "This is a spectacle that has attracted our attention from light years away."