Carnegie: Where Is Earth's Submoon?

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Carnegie: Where Is Earth's Submoon?

Post by bystander » Wed Jan 23, 2019 8:08 pm

Where Is Earth's Submoon?
Carnegie Institution for Science | 2019 Jan 23

Can moons have moons?

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This simple question—asked by the four-year old son of Carnegie’s Juna Kollmeier—started it all. Not long after this initial bedtime query, Kollmeier was coordinating a program at the Kavli Institute for Theoretical Physics (KITP) on the Milky Way while her one-time college classmate Sean Raymond of Université de Bordeaux was attending a parallel KITP program on the dynamics of Earth-like planets. After discussing this very simple question at a seminar, the two joined forces to solve it. Their findings are the basis of a paper published in Monthly Notices of the Royal Astronomical Society.

The duo kicked off an internet firestorm late last year when they posted a draft of their article examining the possibility of moons that orbit other moons on a preprint server for physics and astronomy manuscripts.

The online conversation obsessed over the best term to describe such phenomena with options like moonmoons and mini-moons being thrown into the mix. But nomenclature was not the point of Kollmeier and Raymond’s investigation (although they do have a preference for submoons). Rather, they set out to define the physical parameters for moons that would be capable of being stably orbited by other, smaller moons.

“Planets orbit stars and moons orbit planets, so it was natural to ask if smaller moons could orbit larger ones,” Raymond explained.

Their calculations show that only large moons on wide orbits from their host planets could host submoons. Tidal forces from both the planet and moon act to destabilize the orbits of submoons orbiting smaller moons or moons that are closer to their host planet. ...

Can Moons Have Moons? ~ Juna A. Kollmeier, Sean N. Raymond
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
— Garrison Keillor

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