Wondering What To Call a Moon of a Larger Moon? It's Not That Simple

Thursday, 11 October 2018 - 11:04AM
Solar System
Moon
Thursday, 11 October 2018 - 11:04AM
Wondering What To Call a Moon of a Larger Moon? It's Not That Simple
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It's a scientist's job to ask the important questions and to try and find the answers, but it's the scientist's kid's job to ask the questions that no one knew we needed answers to. According to Gizmodo, Juna Kollmeier, an astronomer at the Observatories of the Carnegie Institution of Washington, was asked by her son in 2014 if a moon could have a smaller moon the way some planets do. Kollmeier didn't know the answer, so she and fellow astronomer Sean Raymond got to work to figure out if submoons (alternately called moon-moons) could theoretically exist.

In a paper posted to arXiv [PDF], Kollmeier and Raymond concluded that moon-moons can exist, but only under perfect conditions. "We find that 10 km-scale submoons can only survive around large (1000 km-scale) moons on wide-separation orbits," they write, adding that "tidal dissipation destabilizes the orbits of submoons around moons that are small or too close to their host planet." Using a complex equation to determine the critical size that a moon would have to be to host a "long-lived" submoon, the astronomers found that a few moons in our solar system are, in theory, capable of being moon mamas: Saturn's moons Titan and Iapetus, Jupiter's moon Callisto, and Earth's very own crater-faced beauty

Because this is all theoretical, there is some debate over what the official term for a moon of a moon should be. Submoon, moon-moon, moonitos, and others have been thrown out there, but Kollmeier tells Quartz that the International Astronomical Union (IAU) would have to decide. The IAU is also the group that came up with the hotly debated definition that caused Pluto lose its status as a planet, so we're not sure we want them to control what we call anything anymore. Moon-moon is the most fun to say, so for now, let's just stick with that.

Goodnight moon-moon.

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