The distant tiny moons were spotted using powerful land-based telescopes in Hawaii and Chile, and announced Friday by the International Astronomical Union’s Minor Planet Center.
The latest tally puts Neptune at 16 known moons and Uranus at 28.
One of Neptune’s new moons has the longest known orbital journey yet. It takes around 27 years for the small outer moon to complete one lap around Neptune, the vast icy planet farthest from the sun, said Scott Sheppard, an astronomer at the Carnegie Institution for Science in Washington who helped make the discovery.
The new moon orbiting Uranus, with an estimated diameter of just 5 miles (8 kilometers), is likely the smallest of the planet’s moons.
“We suspect that there may be many more smaller moons” yet to be discovered, he said.