Astronomers announced that they have discovered new moons around Neptune and Uranus.

The International Astronomical Union's Minor Planet Center published its findings Friday, showing the first new moon discovered around Uranus in over 20 years and two new moons around Neptune.

“The three newly discovered moons are the faintest ever found around these two ice giant planets using ground-based telescopes,” Scott S. Sheppard, an astronomer at the Carnegie Institution for Science in Washington who helped discover the moons, said in a press release. “It took special image processing to reveal such faint objects.”

The newly discovered moon around Uranus is the 28th known moon around that planet, and the moons found around Neptune bring the known total to 16.

How were the moons around Neptune and Uranus found?

Sheppard observed the new moons using telescopes in Hawaii and Chile.

While the moons move at a glacial pace compared to Earth's moon — the smaller of the Neptune moons takes 27 years to complete a trip around its planet — limited opportunities to separate them from the star-scape required astronomers to take "dozens" of long exposure photographs over multiple nights, according to the Carnegie Science press release.

"Because the moons move in just a few minutes relative to the background stars and galaxies, single long exposures are not ideal for capturing deep images of moving objects,” Sheppard said. “By layering these multiple exposures together, stars and galaxies appear with trails behind them, and objects in motion similar to the host planet will be seen as point sources, bringing the moons out from behind the background noise in the images."

Scientists believe that smaller moon fragments around the planet may still be undiscovered, according to the press release.