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Can moons have moons?
- saagarjha 8y ago> which we call submoons I believe the publicly accepted term for these is “moonmoon”.
- newsbinator 8y agoCan moonmoons have moonmoonmoons?
- mywittyname 8y agoAstronomers have adopted Python syntax for further iterations of this. Thus, it is formally referred to as a "moon"*3.
- Matumio 8y agoNo, a "moonmoon" would be the big moon into whose orbit you park the smaller moon. Reference: https://xkcd.com/2043/ https://xkcd.com/2043/
- gpm 8y agoSo, what you're saying is that the earth is a moonmoon of the sun right?
- superice 8y agoIn that case they both would be a moonmoon.
- daveFNbuck 8y agoThat actually doesn't match the meanings of househouse and boatboat in the chart. The hovertext specifies that you can refer to the contained object by flipping the order, so a moonmoon can also refer to the smaller moon orbiting around a larger one: > The <x> that is held by <y> is also a <y><x>, so if you go to a food truck, the stuff you buy is truck food.
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- torstenvl 8y ago"That's no moonmoon..."
- Millennium 8y agoDammit moonmoon, that's not what you're supposed to howl at.
- thrill 8y agoI'm going with moonpies.
- the_duke 8y agoI thought the correct term for anything other than Earths Moon was "natural satelite".
- Freak_NL 8y agoNot at all. The noun 'moon' can refer to any, well, moon (like Deimos or Europa). To distinguish between those and our moon, you can use the proper name 'Moon' (capitalised) or Luna if you are so inclined. The same goes for the Sun. Our sun is either proper name 'Sun', or if your prefer Luna above, Sol. Any other star with stuff orbiting around it is just another sun (noun).
- mehrdadn 8y agoI thought there's only one sun regarding of whether you capitalize it or not, but that moon was generic.
- Freak_NL 8y agoThey are both generic, but because the context of most texts we write is here on Earth, 'sun' and 'moon' tend to be used as proper names would, but without capitalisation. That these are essentially generic nouns can show up more clearly in astronomical texts and of course in literature (science fiction).
- dragonwriter 8y ago“sun” is generic but rarely used as such instead of the proper noun “Sun” outside of interstellar fiction, because “star” is available and denotatively equivalent. (“sun” has a stronger connotation that the object's importance is relative to one or more planets, though.)
- lloeki 8y ago> Luna I have also seen Selene or Selena being used from time to time, more often as a adjective (selenic) but also as a noun every now and then.
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- jobigoud 8y agoI also got interested in this question a few years back and while browsing for candidates I learned about Neso, the outermost (known) moon of Neptune. https://en.wikipedia.org/wiki/Neso_(moon) https://en.wikipedia.org/wiki/Neso_(moon) It is on average further away from Neptune than Mercury is from the Sun! It takes more than 26 years to orbit Neptune, it still hasn't completed a full orbit since we have discovered it. Also, I think there could be "binary-moons", if a binary asteroid gets captured as an irregular moon. Asteroids with natural satellites exist and have been found. There could also be very big trojans moons/planets in other star systems.
- gustavooliveira 8y agoMay someone tell me where this article was published (magazine, congress, etc), please?
- aargh_aargh 8y agoProper link to abstract on arXiv: https://arxiv.org/abs/1810.03304 https://arxiv.org/abs/1810.03304 arXiv is an archive of preprints. This is a preprint. It hasn't been published (yet). In some scientific fields, it's customary to share preprints publicly before they are published. Sometimes they aren't published (i.e. by a peer-review journal) at all.
- gustavooliveira 8y agoInteresting. Thank you aargh_aargh for the information.
- asmithmd1 8y agoTIL: They have detected exo-moons around exo-planets outside our solar system.
- chanandler_bong 8y agoTechnically, aren't planets moons of their star? So if a 'planet' has a moon, wouldn't that be a submoon?
- JumpCrisscross 8y ago> aren't planets moons of their star? No. The difference between “star” and “not star,” within the context of a solar system, is well defined. (Brown dwarfs muddy the line in general.) The difference between “planet” and “not planet” is a little more arbitrary, with the line between “moon” and “non-moon satellite” being more arbitrary still. The all-encompassing term you’re looking for is “satellite.”
- Medox 8y agoTo the Sun, a moon is like a submoon to the planet, so what would be the difference? With enough distance in between it should be possible. Not probable but possible. Submoons will probably clump together much easier in the formation phase of any system and a moon will never capture an asteroid before it's planet does. As the author pointed out, the question remains how stable it is. The almost nonexistent cases (at least in our Solar System) shows how rare it is. Maybe only distance is a factor. Huge Solar Systems with twice the distance between objects will also have more submoons.
- Brockenstein 8y agoWell the moon has had artificial satellites in the past. I imagine it might not be terribly common, but not impossible either. >The almost nonexistent cases (at least in our Solar System) shows how rare it is. It might not exist in our solar system, our solar system isn't a model from which all others operate from. Submoons may be rare, but not because they don't exist in our solar system.
- JumpCrisscross 8y ago> Submoons may be rare, but not because they don't exist in our solar system Sure, "submoons are rare because they're rare in our solar system" isn't a proof. (It's a hypothesis.) But the observation is evidence. In the absence of other evidence, it defines the status quo.
- jobigoud 8y ago> Well the moon has had artificial satellites in the past. I imagine it might not be terribly common, but not impossible either. There are still artificial satellites around the Moon but the problem as stated in the paper is "long-lived" submoons, on stable orbits, which the Moon can't have.
- jessriedel 8y agoThere is a limit to how big planets can get before they become stars, and a limit to how small moons can get before electromagnetism becomes dominant over gravity in determining their motion. So there exists a hard (not just probabilistic) maximum number of levels of submoons. Given other constraints like orbital stability and the Roche radius, it would not surprise me if this number was a low single-digit integer.
- moon_of_moon 8y agoYes.
- S4M 8y agoYour username is well suited to comment this article.
- ape4 8y agoAs programmers, the answer is "of course". Of course a function can call a function. But nature isn't a stack. Can submoons have subsubmoons.
- bawana 8y agoso what is the human behavior denoted by 'moonmoon-ing' someone?
- fxj 8y agoEarth's moon has unstable orbits: https://en.wikipedia.org/wiki/Lunar_orbit#Perturbation_effects https://en.wikipedia.org/wiki/Lunar_orbit#Perturbation_effec... Gravitational anomalies slightly distorting the orbits of some Lunar Orbiters led to the discovery of mass concentrations (dubbed mascons) beneath the lunar surface caused by large impacting bodies at some remote time in the past. These anomalies are significant enough to cause a lunar orbit to change significantly over the course of several days. See also: https://science.nasa.gov/science-news/science-at-nasa/2006/06nov_loworbit/ https://science.nasa.gov/science-news/science-at-nasa/2006/0... Joining an earlier subsatellite PFS-1, released by Apollo 15 astronauts eight months earlier, PFS-2 was to measure charged particles and magnetic fields all around the Moon as the Moon orbited Earth. The orbit of PFS-2 rapidly changed shape and distance from the Moon. In 2-1/2 weeks the satellite was swooping to within a hair-raising 6 miles (10 km) of the lunar surface at closest approach. As the orbit kept changing, PFS-2 backed off again, until it seemed to be a safe 30 miles away. But not for long: inexorably, the subsatellite's orbit carried it back toward the Moon. And on May 29, 1972—only 35 days and 425 orbits after its release—PFS-2 crashed. Be careful of the orbit chosen for a low-orbiting lunar satellite. "What counts is an orbit's inclination," that is, the tilt of its plane to the Moon's equatorial plane. "There are actually a number of 'frozen orbits' where a spacecraft can stay in a low lunar orbit indefinitely. They occur at four inclinations: 27º, 50º, 76º, and 86º"—the last one being nearly over the lunar poles. The orbit of the relatively long-lived Apollo 15 subsatellite PFS-1 had an inclination of 28º, which turned out to be close to the inclination of one of the frozen orbits—but poor PFS-2 was cursed with an inclination of only 11º. edit: added additional information about frozen orbits.
- sandworm101 8y agoOur moon, and those of mars, are special cases. They are most likely the result of collisions involving the host planet and some other very large object. They are bigger and closer than any 'natural' moon formed during the formation of the solar system. So it is expected that they are unsymmetrical both in shape and orbit, resulting in them having few stable orbits for sub-moons. Collisions are certainly part of the equation, but there again many of those collisions were associated with debris from the initial impact that created the moon. A 'natural' moon formed early in the life of a solar system could be much further from its host, with much more symmetrical gravity and many stable orbits ready to host sub-moons. A moon is also in a much better place from which to capture a passing body.
- pbduring 8y agoMost importantly: can moons have morons?
- flexie 8y agoThis is an exception to Betteridge's law, isn't it?
- aj7 8y agoSub-question. Are there any extant man-made objects in orbit around our moon right now? Around any of the planets?
- jbattle 8y agoI know Mars at least has several ... https://en.wikipedia.org/wiki/List_of_Mars_orbiters https://en.wikipedia.org/wiki/List_of_Mars_orbiters
- InclinedPlane 8y agoThe Lunar Reconnaissance Orbiter is still in operation, as are ARTEMIS P1 and P2. There are several spacecraft orbiting other planets (both functional and inactive) but none orbiting any of the moons of other planets, if that is what you mean.
- jobigoud 8y agoCurrently active: 1 around Venus, 4 around the Moon, 6 around Mars, 1 around Ceres, 1 around Jupiter. https://en.wikipedia.org/wiki/List_of_extraterrestrial_orbiters https://en.wikipedia.org/wiki/List_of_extraterrestrial_orbit...
- SubiculumCode 8y agoSo the moon has a moon, but I'd guess that the orbit is not stable over the long term.
- SubiculumCode 8y agoOf course this is just within the arbitrary distinctions of what constitutes a moon and a planet. A particle of sand in the Sahara desert orbits the earth's core albeit with a lot of collisions with other sand moons.
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- cleanyourroom 8y agoDOUBLEMOON