A team led by Carnegie’s Scott S. Sheppard has found 20 new moons orbiting Saturn. This brings the ringed planet’s total number of moons to 82, surpassing Jupiter, which has 79. The discovery was announced Monday by the International Astronomical Union’s Minor Planet Center.
Each of the newly discovered moons is about five kilometers, or three miles, in diameter. Seventeen of them orbit the planet backwards, or in a retrograde direction, meaning their movement is opposite of the planet’s rotation around its axis. The other three moons orbit in the prograde—the same direction as Saturn rotates.
Two of the prograde moons are closer to the planet and take about two years to travel once around Saturn. The more-distant retrograde moons and one of the prograde moons each take more than three years to complete an orbit.