A tiny moon has been discovered orbiting around the gas giant Neptune.
It has been called Hippocamp and the minuscule world measures only 21 miles (34 kilometres) in diameter.
It was spotted by scientists carefully studying old images from Hubble showing the six other moons inside the orbit of Neptune’s largest satellite, Triton.
The moon is so small that Voyager 2 missed it when it flew by the planet in 1989.
This discovery takes the total number of moons orbiting Neptune to 14.
Hippocamp got its name from the sea creature of Greek mythology and becomes the smallest of Neptune’s satellites.
It orbits close to Proteus, the largest and outermost of the inner moons with a diameter of 261 miles (420km).
Scientists from the SETI (Search for Extra-Terrestrial Intelligence) Institute in Mountain View, California, say in the paper, published in Nature, that it was likely formed from fragments of Proteus after a collision with a comet.
Researchers say the discovery of Hippocamp supports claims the inner moons were formed by numerous impacts over time.
Dr Mark Showalter, of the SETI (Search for Extra-Terrestrial Intelligence) Institute in Mountain View, California, said: ‘Hippocamp is smaller than the other six.