A huge telescope has begun searching for light messages that could have been sent to Earth by aliens.
Scientists in the US are using the optical telescope to look for any light signals being beamed across the universe by other civilisations.
The telescope will scan the skies for a year, searching the Milky Way galaxy visible in the Northern Hemisphere.
Some experts think aliens, if they are out there, would be most likely to communicate using light-beams.
Scientists working on the Search for Extraterrestrial Intelligence (SETI) project are looking at the cosmos for technology built by alien beings.
The new telescope has a 1.8m mirror and is the first the SETI team have dedicated to the mission to find aliens.
"We have been listening for alien signals for decades," said Louis Friedman, executive director of the Planetary Society, which funded the telescope's development.
"It's time we started to watch for signals as well."