Gas Giant Moon Systems and Habitable Moons 

that's actually a pretty cool analogy for two moons; nice work

@@goofyahhgamer4827 my planet's name is alreadyi it's a gas giant size of Saturn it's small but dancer it's a bluish color it has a moon has oceans continents and Life the Moon is smaller than Earth less denser it has ocean seas made of saltwater the gas giant is not visible in the sky it's atmosphere is made of methane and Ethan and oxygen it offers the gas giant of a distance of two lunar distance it has no intelligence species but still life the Moon's name is oka it's actually the smallest of the gas giant the largest mood of the gas giant is not named and it's the signs of Mars

Sounds Irish or Greek

Ok thats good byt a kid wont call him ELDER xyani. Instead, xyani

@@smartart6841 you do realise that this hypothetical alien culture is completely different from your own, right?

John Maguire well it aint habitable on the surface

test_johndoge still habitable under the surface

Lemob i know but the way they implied it seemed like they meant on surface

test_johndoge ah ok

I could imagine life evolving on an ocean floor and over the course of time adapts to utterly inhospitable terrestrial conditions.

Good thing the universe is infinite. So no matter how improbable it is, if it has even the slightest chance of existing/happening it will happen somewhere at some point

@@macaroon_nuggets8008 There is far too little data to claim infinity, it is a much greater chance that the universe is finite. There is a great deal of data to suggest that the universe is expanding, if it is expanding then it has a border and is not infinite. We can only know what we observe and there is just so much that we do not know, all we know is what we can see outward from within our solar system so far.

@@blastyfs2 *shhhhhhh* , you are ruining it!

blastyfs2 even if it’s not infinite it’s several million times bigger than the amount of ways quantum particles can be arranged, so anything that can happen, will happen. Edit: it would actually probably be replicated several times due to the sheer amount of space in space

Humans: "This looks a bit... errr... hum... improbable..." Reality: "Shut up!!!" Is far more common

Or create it by smashing something.

Both. It could wreck the rings or it could cause further collisions and create new rings.

that's another problem, the giant satellite would mess up the orbits of other satellites, either throwing them out of the system or causing them to spiral in towards the gas giant, or best case scenario their orbital eccentricites increase/decrease

Look at Neptune. His moons were affected by the capture of Triton, especially the outer moons like Halimede, Nereid and Sao. The former inner moons were broken apart and reformed as six of the seven inner moons. Hippocamp was formed when it was knocked off Proteus. Neptune may have gotten his rings due to this too.

@@papisuckmypoosay69 If you're going with the capture method, most of the natural satellites of a gas giant migrating inward would get lost during the migration. This is due to interactions with intervening protoplanets, changes in tidal forces from the increasing proximity of the sun upsetting previously stable orbits, and just the amount of time such a migration would take. A quick web search found a fun Harvard study on the subject from 2001. The loss of moons is one reason mentioned in this video why Artifexian chose the captured moon scenario for the focus of the video.

When you have a sample size as big as the universe, 'probably not' means 'most definitely'

@@gingermcgingin1733 but considering that the universe is much bigger than Russia the closest of such moons could be as far away as 1000 light years or maybe such an earth like horseshoe moon may not even exist in our galaxy

2 years away

@@extratropicalcyclone8567 Much bigger than Russia? That's a weird way of putting it.

@@gingermcgingin1733 the odds are astronomical

and the space-age planet visits the bronze-age planet and is like "whaaaat"

You mean a movie, right? I can totally see this as a Star Trek episode!

Just imagine how each civilisation would portray the other, as in, how the less advanced civ would see a world that would always pop into existence and recede into nothing; could that civ see that as their future (or demise) literally popping in and out of their existence?

I can write a book from the technological civilizations standpoint, and switch between the 2 after they land on the other moon :)

***** Yep, see a new thread in the lounge :)

It's true though

Me too.

he had me at "one radii" ;-)

This gave me a hearty chuckle. 😄

Oh

How.

I was simulating a debris disk around a star (akin to a white dwarf to make it easier on my computer), basically to see how the planets would naturally form, with placing metals, non-metals and ices in different parts of the disk. Two earth-like planets formed near each other, were gradually shifted closer by the other planets, and then it just... happened. I played it for another few thousand orbits, but they continued to work. They were both habitable too, outer one with ~90% ocean coverage, and the other with ~25%, factoring in reasonable greenhouse effect. Although I couldn't really simulate that part, I imagine at their size they would have had comfortable atmospheric pressure and magnetic fields. It was really cool!

Mine too. Truth really is stranger than fiction.

Science always better than magic.

+Artifexian Earth actually has a horseshoe orbit with an asteroid, going by the name of Cruithne. You should look it up. Also, you sound Irish, so here's a question from a Dutchman learning Irish. An bhfuil aon Gaeilge agat? If so, you're going to be able to pronounce the name of Earth's pseudomoon perfectly :)

​@@bemk It is not a horseshoe orbit. It is just a normal elliptical orbit with a semimajor axis of 1 AU.

By water world. He means NO ROCK AT ALL (maybe a little tiny core tho.) So no ocean floors just water. Whule earth has ocean floors.

@@macaroon_nuggets8008 umm it does not need to be rockless It just have to be REALLY deep

@@jakeariel3974 you are right but I missed my point. The comment (not my reply) said early earth was a water world. It was, but Artifaxian meant water world as moslty composed of water, not the surface fully covered in water.

@@macaroon_nuggets8008 oh ok

@@macaroon_nuggets8008 now I’m imagining a water world that looks like an Earth-like water-rock hybrid but has at least half of its water content in the poles waiting for Global Warming to release it.

Awesome sauce. That's what I like to hear.

I dunno about this, I haven't read anything deal with this set up around stars. But you can of course always handwave these things if the story calls for it.

@@Artifexian I feel like the days of darkness every month from having the Sun eclipsed by Jupiter will mentally prepare cultures for getting the sun eclipsed by the other planet that looks like themselves.

@@Artifexian So I did some looking. There are solar-orbiting horseshoe-orbit bodies. In our solar system, 3753 Cruithne is a big name. So yes, totally possible :)

Feel like that would cause some freaky shit to happen with their moons. Either pulling them out of their orbit causing them to hold a long term grudge and some point cause one of the planets apocalypse. Or would just outright crash the moon if they were in tidal resonance by slowly pulling the moon closer and closer until it got close enough to crash/rip atmosphere or fling out and get caught by the other planet. That being said. A moon isn’t needed for life to form. I would highly doubt that any moon on the size ratio of earths would form

Cheers, buddy! :)

The moon would be tidally locked to the gas giant, and as such its day would be the same length as its orbital period. Tidal locking is virtually guaranteed due to the high mass of the gas giant. One side of the moon would face the gas giant, while the other would never see it. The side that faces the gas giant will experience eclipses during spring and fall (if the gas giant has little to no axial tilt, the moon will experience eclipses throughout the year). In addition, depending on how close the moon is to the gas giant, the side that faces the gas giant may be illuminated by the gas giant at night, perhaps even bright enough to function normally outside!

if the moon is tidal locked, wouldn't there be a "band" zone where all the eclipses happen ? Also do you know any way to calculate an estimate of the sky degrees that a gas giant would occupy from a viewer on the moon ? :D

Efflam Mercier Yes, eclipses will only happen on the hemisphere of the moon that faces the planet, if the moon is tidally locked. This is simply because the planet needs to be in the sky in order to eclipse the star. As for calculating the estimate of degrees, use the formula here: en.wikipedia.org/wiki/Angular_diameter 2*arcsin*(moon diameter / 2*moon distance) I believe.

Fun thing about tidal lock on gas giants is that their orbit might not be as long as most people think they are. Io for example takes 1.7 days to go around Jupiter. Edit: thanks for the formula btw.

3d bc 5b e3 c4 d5 05 a4 cb df Since the tidally locked side would experience little to no real sunlight beyond what is bounced off of the gas giant, could we expect one side to be colder than the other during the opposing side’s day (that is, when it faces the sun)? Similarly, could we expect it to be colder during that same side’s night (when it is facing away from the sun and is the moon is basically eclipsed), and could we expect these differences in temperature to cause storms surging from one side of the moon to the other?

He did a video on that. Basically it sums up on moons having a Rouche limit too. If you have the mass of the moon, you can calculate the Moon's moon. But like he said, probably water worlds (which are not bad)

Enkii Muto Thanks for the info.

Moons can't have moons - at least, not for very long. This is because of tides. You may have heard that tides from our moon are slowly making our day longer and causing the moon to move farther away. This is because the moon raises what's called a tidal bulge on Earth, distorting the planet's shape from the normal oblate spheroid. Now, after a given period of time Delta-t, the earth has rotated X degrees and the moon has rotated Y degrees. Since the Earth rotates faster than the moon orbits (earth rotates about 28 times per lunar orbit), X > Y, and the tidal bulge rotates ahead of the moon. This causes the moon's gravity to pull slightly more on the "leading" side of the Earth, creating a torque in the opposite direction of Earth's rotation and slowing it down. By Newton's Third Law, this also means that the moon is pulled forward, causing it to move faster and slowly migrate into a higher orbit. The Earth has the same effect on the Moon's rotation, but since the Earth is much more massive than the moon, the moon long ago became "tidally locked," meaning its rotational and orbital periods are identical and it always keeps the same face towards the Earth. This happens to other moons as well. A very large moon, such as Charon, can also tidally lock the parent planet, but gas giant moons are usually too small to do this. Now, here's the problem. If the moon is orbiting FASTER than its parent rotates or is in a retrograde orbit, then this effect works in reverse, causing the moon to spiral inwards until it passes its parent's Roche Limit and is destroyed. This will happen to Mars's moon Phobos in a few tens of millions of years, and to Neptune's moon Triton in about a billion years. The effect is less severe for small objects held together by tensile strength and not just their own gravity, which is why the tiny particles making up planetary rings can last for a long time. Now, let's imagine a moon of a moon. Because of the way orbital mechanics work, a subsatellite, whether it's a moon of a planet or a moon of a moon, must have an orbital period significantly shorter than its parent (continued).

(continued) we can derive this from the formula for the Hill Sphere radius: r ~~ moon orbital distance * (mass of moon / 3 / mass of planet)^1/3. In practice, moons are usually only stable within 1/2 of the hill radius, so the max "stable" orbital distance of a subsatellite is the above formula / 2. We can plug this distance into Kepler's third law: an object's orbital period, if it is much less massive than its parent, is the sqrt(orbital distance^3 / mass of parent) * a constant. Basically, after a lot of algebra the orbital period of a satellite cannot be longer than about 1/5 its parent's orbital period. But recall that the moon's rotational period is equal to its orbital period due to tidal locking, so the moon of a moon's orbital period MUST be shorter than its parent's rotational period. Therefore the moon of a moon will gradually spiral inward due to tidal drag, and eventually either break up or impact its parent.

Omnigeek6 Thanks for the info.

@KvAT protip: at least for binary stars, if you put planets around them in retrograde orbits relative to the orbital directions of both stars, the stability for those orbits absolutely skyrockets

Mine too... Edgar is the man!

Without Artifexian, I wouldn't have been able make my planets as scientifically-backed or become inspired to create the systems and planets I have after checking him out. Thank you Edgar!

Issac Arthur did a video on that called Double Planets.

Ye, it was pretty dense alright. I wrestling with the idea of doing big dense videos (8-12 mins) or shorter, lighter videos (3-4 mins). Think of this, I will.

Artifexian Personaly I think dense videos are better.

My guess is he was trying to keep it "simple".

I've also thought about this scenario, but it would be really bad for the orbits over time, causing the plant to fall into the giant Roche limit.

I think the better way to get heat out of Jupiter would be to drop a micro black hole with a mass of 1*10^27 kg and a radius of ~100X smaller than a human hair into Jupiter. This will then cause gas and dust on the inside to spin around it really quickly, giving off enough heat from friction between the spinning particles to push material away from the black hole, thus creating a very slow equilibrium of heat being released as matter falls in. After 1 million years, Jupiter would get hot enough from this interaction to (at Jupiter’s current distance from Earth in our universe) be 50X brighter in the sky than the full Moon. Such a bright Jupiter as this would be able to support habitable planets much further out in gravitationally stable orbits with the category C moons (the captured moons), even with Jupiter itself being outside of the Sun’s habitable zone. The funny thing about this setup will be how the cultures evolve to see with more reddish light and infrared light, and what they will think of the much brighter Sun that is so much smaller and disappears behind the “dull red sun” of Jupiter. The one annoying thing about this design is that we will need to have a way to extract mass away from Jupiter while it is burning to make sure it stays at the same temperature (shunting the excess hydrogen over to a new Saturn-sized planet), since otherwise the temperature of Jupiter will increase 10X over the course of 100 million years (just based on how the equilibrium point for the micro black hole will change as it absorbs more mass).

@@evannibbe9375 I'm pretty sure that stuff spins around black holes merely for the same reason that planets spin around stars, rather than black holes having some property that magically prevents incoming objects from taking a straight line.

Thanks, Rene. You are awesome.

And you deserve WAY more subscribers for the amazing content you produce.

That it would

Other Moons?

Incredible luck and random chance. The universe is basically infinite, there must be a real example somewhere!

Tidal dampening as it orbits around the gas giant. Look at Triton, for example.

thanks everyone for your answers, I see there are ways to lower exentricity I did not know off.

Maybe you know that the tidal force locks planets, forcing them to spin with orbital period, so if planet on elliptical orbit, it cannot rotate synchronous because of different speed at apoapsis and periapsis. Orbital energy of the planet converts into heat until spin-orbit resonance is established (like Mercury).

wow, I haven't seen Fern Gully in ages. :)

Whatever it was it really was a pretty poor excuse for an "original" movie.

It was "Dances With Wolves" IN SPACE.

35K blows my mind. I never thought so many people would be into my little nerdy hobby.

*158k

John Jowers how would they switch position without collisions when crossing the cloud?

Moon Brown presumably the showers of interplanetary dust are part of the plot.

Could you imagine that? Suddenly there's a massive meteor shower as another planet races forward from the black void of space, becoming bigger and bigger until, suddenly, it begins to recede away again. I can't even begin to imagine how this would affect the cultures of an arising civilization!

So does mine, named Algodoo and Phun. No dust band however. They are part of a system of sixteen planets orbiting a G3V star named Algo.

I think radiation belts are a little too complicated for this channel. Plus, I remember reading something whilst researching this video that implied that large enough moons could be habitable despite being in the belts.

Artifexian Interesting, I've never heard that. But then I don't know much about this whole fictional astronomy thing :)

I had a look at this Jupiter as an examples the main radiation belt is relatively close to the planet 3 R and the entire magnetosphere only extends 22 R and 20 R is the maximum of what is recommended in this video for orbit meaning your earth like planet would only be 2 R inside the magnetosphere and if you have a slightly weaker field for some reason gas giant there will be no problem, for example slightly smaller gas giant, more rings and debris to adsorb the radiation or maybe a stronger magnetic field for the earth like as it’s what protects the planet from the radiation I’m being overly cautious because I’m not a science nerd but I’m pretty sure in theory you should be fine even at 15 R because the radiation belt is really only within a couple of R of the gas giant The bigger thing you have to worry about is tidal forces I haven’t looked into this yet but it’s probably way less of a problem at 15-20 R than less than 1 R as in the earth orbiting Saturn partly in the rings video edit because in that example you’re basically within the Roche limit so the tidal force is literally enough to destroy the planet lol

@@johnathonyoung4799 Europa for example is absolutely showered by radiation, let alone Io.

@@unvergebeneid oops I used Saturn and not Jupiter

that sounds epic... so much potential. Follow your dream and make it happen bro. I'll hope to see the table top books soon and the MMO in 5 years. Good luck.

Do your moons/worlds have to be "natural"? You can just say they were designed and built by powerful mages or an advanced race who have long sense left this galaxy/region.

***** hmm ancient race would work, not really wanting this to be a super magic universe.

Bryan Lariviere cool. :)

Thats what i use this for too

Huzzah!

+Artifexian Minecraft!

+Artifexian Minecraft!

+Artifexian artifexian, look at the top comment of this vid!!!!