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posted by mrpg on Wednesday March 14 2018, @12:06AM   Printer-friendly
from the moon-is-the-loneliest-star dept.

The Fate of Exomoons when Planets Scatter

Planet interactions are thought to be common as solar systems are first forming and settling down. A new study suggests that these close encounters could have a significant impact on the moons of giant exoplanets — and they may generate a large population of free-floating exomoons.

[...] Led by Yu-Cian Hong (Cornell University), a team of scientists has now explored the fate of exomoons in planet–planet scattering situations using a suite of N-body numerical simulations. Hong and collaborators find that the vast majority — roughly 80 to 90% — of exomoons around giant planets are destabilized during scattering and don't survive in their original place in the solar system. Fates of these destabilized exomoons include:

  • moon collision with the star or a planet,
  • moon capture by the perturbing planet,
  • moon ejection from the solar system,
  • ejection of the entire planet–moon system from the solar system, and
  • moon perturbation onto a new heliocentric orbit as a "planet".

[...] An intriguing consequence of Hong and collaborators' results is the prediction of a population of free-floating exomoons that were ejected from solar systems during planet–planet scattering and now wander through the universe alone. According to the authors' models, there may be as many of these free-floating exomoons as there are stars in the universe!

There are no confirmed exomoons yet. Rogue planets may have their own satellites as well.

Innocent Bystanders: Orbital Dynamics of Exomoons During Planet–Planet Scattering (DOI: 10.3847/1538-4357/aaa0db) (DX)


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  • (Score: 2) by Grishnakh on Thursday March 15 2018, @12:17AM

    by Grishnakh (2831) on Thursday March 15 2018, @12:17AM (#652700)

    "rogue planet" would be ok, if they revise the definition of planet so it doesn't say "clears its orbit"

    Again, they don't need to do that: they already did that with "dwarf planet" (which everyone now knows isn't a "real" planet, because it isn't large enough to clear its orbit). As I said, it's like toy cars vs. cars. If you ask me what kind of car I have, and I say I have a Corvette, and you go "wow! I'd like to check that out!" and then I pull a Matchbox Corvette out of my pocket, you're going to be annoyed or amused, but you won't think it's a "real car", though it certainly is a "toy car", and then you're probably going to ask what kind of car I *really* have.

    so it doesn't say "clears its orbit" ... which even Jupiter doesn't do. (See Trojan Asteroids, Lagrange, etc.)

    This is wrong. Here's the Wikipedia page [wikipedia.org] about it. The trojans are in orbital resonance so they'll never collide with Jupiter. It's not about making sure there's no other bodies in that particular orbit, it's about making sure there's nothing nearby that's likely to collide with it. It's also not black-and-white, as it's impossible to completely clear the orbit, so they came up with some mathematical formulae to discriminate between them. The major planets score order of magnitude different by these measures than the dwarf planets, so it works out pretty well.

    Of course, you're not alone in your disagreement: the guy who leads New Horizons also doesn't like the new definition (he also cites the Trojans), but he also helped come up with one of the algorithms to distinguish major and minor planets, so he also seems to recognize the need for discerning between larger planets like Jupiter and Mercury and tiny ones like Makemake and the various other TNOs and KBOs out there.

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