The Hubble space telescope has discovered a new moon orbiting Neptune, Nasa has confirmed, the BBC reports.
Designated S/2004 N 1, this is the 14th known moon to circle the giant planet.
It also appears to be the smallest moon in the Neptunian system, measuring just 20 km across, completing one revolution around Neptune every 23 hours.
US astronomer Mark Showalter spotted the tiny dot while studying segments of rings around Neptune.
Nasa said the moon was roughly 100 million times dimmer than the faintest star visible to the naked eye.