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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)
(Score: 2) by PartTimeZombie on Wednesday March 14 2018, @01:07AM (4 children)
Considering things as small as 243 Ida [wikipedia.org] can have a moon, maybe moons are really common.
The problem with poor old astronomers is that the observations they need to make are of tiny things a long way away, or they need to observe stuff over really long periods.
They must all dream of a telescope outside Pluto's orbit, which I imagine would be a help.
(Score: 3, Interesting) by Grishnakh on Wednesday March 14 2018, @01:20AM (3 children)
They must all dream of a telescope outside Pluto's orbit, which I imagine would be a help.
I seriously doubt it. The distance from Earth to Pluto's orbit is a tiny fraction of the distance from Earth to the nearest star system (Alpha Centauri), and to further star systems it's insignificant I'm sure. A telescope out there isn't going to help. A radio telescope on the dark side of the Moon would be helpful, though, for getting away from our radio noise here. And of course, a telescope in space, outside of Earth's atmosphere, is a big help, which is why they built Hubble and now are working on the JWST, but sticking a space telescope farther away isn't going to do much good, unless of course you could get it *really* far away, but that isn't feasible since it'd take forever to move it there (assuming it even still works), and radio communication would be ridiculously slow to get the data from it.
What we need to do is figure out how to do FTL communications, and also how to open a wormhole and send inanimate objects through it, so we can build a fleet of space telescopes and transport them around the galaxy and then operate them remotely. Of course, if we could do that, we could just build ships and go there ourselves to take a look (and better yet, start a new colony in a far-away star system, so we can get away from the idiots here!).
(Score: 3, Interesting) by takyon on Wednesday March 14 2018, @01:41AM (2 children)
Actually, a telescope *past* Pluto can help. But it has nothing to do with Pluto and it actually needs to be over 550 AU away from the Sun:
https://en.wikipedia.org/wiki/FOCAL_(spacecraft) [wikipedia.org]
https://www.technologyreview.com/s/601331/a-space-mission-to-the-gravitational-focus-of-the-sun/ [technologyreview.com]
https://www.centauri-dreams.org/2006/08/18/the-focal-mission-to-the-suns-gravity-lens/ [centauri-dreams.org]
https://www.newyorker.com/tech/elements/the-seventy-billion-mile-telescope [newyorker.com]
Proxima Centauri is about 268,331 AU away, so 550 AU is about 0.2% of that distance. If Planet Nine exists in its hypothesized orbit, it would probably be around 700-1000 AU away. So that's two potential missions to around that distance that we may see attempted in our lifetimes. In order to get there in less than 20 years instead of 100 years, we could use newer propulsion technologies, an expendable BFR or similar rocket to achieve a lot of delta-v (and the rocket could also be refueled in orbit at least once), and a gravitational assist using the Sun instead of Jupiter.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 3, Informative) by Grishnakh on Wednesday March 14 2018, @03:38AM (1 child)
Yeah, we talked about this FOCAL idea a couple days ago here. But I don't think that's what the OP was talking about, I think he was talking about just getting out there to get a better look at stuff outside our system in general. The problem with FOCAL is that it's only useful for looking in one very particular direction (towards the Sun, to use it as a gravitational lens). That's great and all if you just want to look at one thing (like Proxima Centauri), but it does mean you have a very limited-use telescope.
Also, according to your article at technologyreview.com, 550AU won't work anyway: the telescope has to sit at 2000AU and will have a ridiculously hard time actually locking onto something and imaging it. Honestly, I don't see how the whole thing could possibly work, after reading that article. Maybe a few centuries from now, once we have settlements elsewhere in the solar system and the technology to attempt this.
(Score: 2) by toddestan on Thursday March 15 2018, @11:46PM
One benefit of a regular telescope way out there would be to take parallax measurements to determine the distance of other objects in our galaxy with precision. Basically take a picture of something from the telescope and from the Earth, and measure how much the object shifts from the background between the two shots. You can then use your geometry skills to determine how far away the object is. This technique is already done on Earth - take two shots 6 months apart and the base of the triangle you can make is 2 AU. With a telescope that far out, the base of your triangle could be in the hundred's of AU.