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This image collage features Saturn and the moons Titan, Enceladus, Dione, Rhea and Helene, which will be studied in the extended mission. (NASA/JPL/Space Science Institute)

Since Galileo and Copernicus, most of humankind has understood that planets orbit our sun and that moons orbit the planets. Astronomers have also shown that there are planets in other solar systems outside of ours called “exoplanets.” Furthermore, the definition of a planet has been refined with much criticism as Pluto got downgraded to “dwarf planet” status. Now, it has been revealed that there might be even smaller objects orbiting moons that have been bestowed the ignominious title of “moonmoons.”

According to recent reports, there might be “skyscraper-sized” objects orbiting the moons of Earth, Jupiter and Saturn. If a combination of two factors is met, if the moon is sufficiently large and distant from the planet it is orbiting, there is a good probability of it having moonmoons. Astronomers studying this phenomenon call this the “Goldilocks zone,” where the moonmoon is tethered close enough to its cognate moon gravitationally to prevent it being pulled away by the planet, but far enough away to not get pulled into the moon by its gravitational field. Within our solar system, there are three planets that meet these criteria: Earth, Jupiter and Saturn. Specifically, moonmoons have been speculated to exist in the orbits of Saturn’s moons of Iapetus and Titan, Jupiter’s moon of Callisto, and Earth’s single moon.

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