NASA/JPL-Caltech/Space Science Institute

Moons of moons could exist, and scientists call them ‘moonmoons’

Imagine our sun as a cake, the planets orbiting around it as cupcakes, and the moons orbiting them as minicupcakes. Could there be another level of miniminicupcakes orbiting around those moons? Yes, according to new calculations, and it would be called a “moonmoon,” New Scientist reports. But the setup would be tricky: A moonmoon would need to sit in a “Goldilocks zone” close enough to remain gravitationally bound to its host moon instead of the planet, but far enough away to not get drawn in by the host’s gravitational force, the researchers report this week on the arXiv preprint server. Although a moonmoon has yet to be spotted in our solar system, the team points out four theoretical candidates to host such a body—Earth’s moon, Jupiter’s moon Callisto, and Saturn’s moons Titan and Iapetus.

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