ALIEN: The Weyland-Yutani Report (S.D. Perry, 160 pages)

[426Buddy]

I don't think that's in the movie.

I dont think so either... But man what a great pic, looks so cool.

[Local Trouble]

Submit.  Conform.  Obey.

[Nostromo]

This is where all that info came from: (What is right and what is wrong?)

LV-426 2,213 miles in diameter (3,540km) (Source is......but a very believable size for a nice large Gas Giant moon)
http://www.scified.com/topic/17394 says he copied it from Aliens Wiki?

Calpamos 117, 925 km (Not a reliable source at all, but a very believable diameter for a large Gas Giant)
https://www.pinterest.com/pin/238972323947833168/ & http://pics-about-space.com/floating-alien-gas-giant?p=4

Here it says LV-426 is only 1,200km (Highly unlikely that LV-426 is so small, from the space scenes in Alien, unless Calpamos is really small?)
http://aliens.wikia.com/wiki/LV-426 & http://weyland.wikia.com/wiki/LV426

Here it says LV-426 is 12,201km in diameter
http://avp.wikia.com/wiki/Acheron_(LV-426)

And the most ridiculous one: Here it says Calpamos has a diameter of 8,800km
http://weyland.wikia.com/wiki/Calpamos

I think the most important thing is to find out Calpamos's real size first...anyone know...? and it can't be more than twice the size of Jupiter, because than your in bozo science territory.

But, it might be possible for a Jupiter sized planet to have a moon the size of Earth (12,742km) as some say here https://www.quora.com/Is-it-possible-for-an-earth-sized-planet-to-orbit-as-a-moon-around-a-gas-giant

Answer 1. An iron-based planet such as the earth would be too heavy and tidal forces would break it apart. Any large moon would have to be composed of much lighter elements, such as styrophonium.

Answer 2. Maybe not. If it were not tidally locked, the tidal forces would generate a lot of heat, and melt it or even break it apart and it would never get to be tidally locked. After all the largest moon in the solar system is only 2.5% of Earth's mass, perhaps that is the reason.

Answer 3. On a Super-Jupiter or Brown Dwarf yes, (provided that your Planet is outside the radiation belt). Natural Moons of Gas Giants their mass should be less than 0.0001 of the mass of the gas Giant.

Jupiter's moons are pretty massive, but not as massive as Earth, so a Super-Jupiter would suffice. Saturn who's less massive, has less massive moons, Uranus even less.

There would be one problem, Gas Giants form out beyond the frost Zone (that we know of, we don't have gas giants closer in our Solar system for reference, but we see a lot of Hot-Jupiters though) so the moons of the Gas giants would be Water worlds if they're in the Habitable Zone of the parent star (the Gas giant can also generate heat for the moon).

A captured moon is completely plausible though. I wouldn't be surprised if Jupiter moved in and captured the rocky planets of our solar system. Fun fact: Triton is a moon caught by Neptune, so this even exists in our solar system. (Jupiter doesn't move in from perturbations of Saturn.)

Answer 4. The physics would work and it has been used a lot in Science Fiction.  But as User says, moons are likely to be much smaller.

An inward-migrating giant might pick up a rocky planet as a new moon.  That would probably mean a very eliptical orbit.

It's also possible that moon-formation in our solar system is not typical and that much bigger moons can form without a capture or the sort of collision that formed the Earth-Moon System.

The scietific answer: Tidal locking gives a formula for the time until tidal locking of a satellite's rotation:

tlock≈6 a6Rμmsm2p×1010  yearstlock≈6 a6Rμmsmp2×1010  years

where a is the satellite-planet distance in meters, R is the satellite's radius, the m's are the satellite and planet masses in kilograms, and μ is the satellite's rigidity, which can be roughly taken as 3×10^10 N/m^2 for rocky objects.

Plugging in Earth's radius and mass and Jupiter's mass of 1.8986e27 kg:

\frac{6\cdot 6371000 \cdot a^6 \cdot 3\times 10^{10}}{5.9736\times10^{24} \cdot 1.8986 \times 10^{27}^2}\frac{6\cdot 6371000 \cdot a^6 \cdot 3\times 10^{10}}{5.9736\times10^{24} \cdot 1.8986 \times 10^{27}^2}

5.326239e-62 (orbital radius)^6   <   1

orbital radius  <  16.3028 million km

This is a distance similar to Jupiter's outer satellites.

Last answer: An author called Neil Commins answered that question is his book:
What If the Earth Had Two Moons?: And Nine Other Thought-Provoking Speculations on the Solar System.

[𝔗𝔥𝔢 𝔈𝔦𝔤𝔥𝔱𝔥 𝔓𝔞𝔰𝔰𝔢𝔫𝔤𝔢𝔯]

That's a pretty pointless photograph Trouble. There are no familiar objects in the distance which can give you a point of reference with regards to scale.

The image below better illustrates how truncated the horizon is. Notice how close that flag is sitting to the horizon (click on image to enlarge).

And yet the curvature isn't apparent on both sides of that photo.  The horizon is a non-issue because we never get a view of it on LV-426 that isn't obscured by terrain or atmospheric haze.

No, I was talking about distance to horizon. You'd have to be pretty high up to see the curvature of the moon. To see the curvature of Earth you need to be at least above 50 000 feet. That's a bit higher than most commercial airliners fly, but something like a F-15 or Mig 29 should get you there.

Buzz Aldrin actually remarked on how "disoriented" he felt on the moon because of the close horizon.

But I agree, it's a non-issue in this case since LV-426 is way too rugged to make out the horizon.

Submit.  Conform.  Obey.

You're really insufferable today aren't you Trouble. 

[Local Trouble]

I get cranky when SM isn't around.

[SiL]

Using the painting of the planet and the moons to try to gauge their actual size is going to leave people with headaches as the painting ain't intended for accuracy.

[Xenomrph]

Wasn't about 95% of the CMTM made-up fluff?

That doesn't really change what I said - the stuff sourced from the movie, it does get right much, much more than it gets wrong.

Do you have an example of something it got right that it didn't fabricate to begin with?

I'd have to re-read the Tech Manual (which I've been meaning to do, it's been a long time since I gave it an in-depth reading). I'll get back to you.

Oh, unrelated, but Local Trouble did you get that PM I sent you several weeks ago?

It's hardly wrong if it's going by the source material.

It is if the "source material" is wrong.

If you insist.  I maintain that the source material can never truly be fixed by the EU.

It's more a case of the "source material" providing two contradictory things (what Lambert says, vs what the movies show), and an EU source provides an easy and obvious solution that even lines up with the other things said in the deleted scene (such has LV-426's gravity).

Or in other words:

The simple fact is Acheron can't be as small as the deleted scene says it is because it would be visibly curved when you're standing on it, which it isn't in Alien and it definitely isn't in Aliens.

There's a few on the DVDs.  Can't seem to find a decent one online though.

Here's an interesting pic I found that was obviously analyzed by someone else already.

How could you tell when the planetoid's surface is covered in uneven terrain like mountains and valleys?  Wouldn't you need an unobstructed view of the horizon?

Besides, our own moon is definitely a bit larger than LV-426, but photos of the Apollo astronauts walking on the surface don't reveal any obvious signs of curvature on the horizon.

Well you can kinda see the curvature of the horizon in that moon photo, but it's worth pointing out that earth's moon is 3474km in diameter, meaning it's nearly 3x the alleged size of LV-426. The Nostromo crew wouldn't be able to safely walk on it because it's too small to have the appropriate gravity demonstrated in the movie.

The simple fact is Acheron can't be as small as the deleted scene says it is because it would be visibly curved when you're standing on it, which it isn't in Alien and it definitely isn't in Aliens.

I don't think that's correct either. I did some snooping around and found some proof, therefore you are guilty of deceiving us lol.

Seriously though, checkout these 2 links, it explains it well enough as do the pictures above and in these links.

Also, our moon is roughly 87km smaller in diameter than LV-426. Pretty much the same views on the moon. Whichever has a flatter surface

Earth's moon is 3474km in diameter, almost triple that of LV426's alleged 1200km.
1200km is seriously tiny. As in, half the size of Pluto.

As for a gas giant being 10x the size of Jupiter, it's not impossible.

[Nostromo]

The simple fact is Acheron can't be as small as the deleted scene says it is because it would be visibly curved when you're standing on it, which it isn't in Alien and it definitely isn't in Aliens.

I don't think that's correct either. I did some snooping around and found some proof, therefore you are guilty of deceiving us lol.

Seriously though, checkout these 2 links, it explains it well enough as do the pictures above and in these links.

Also, our moon is roughly 87km smaller in diameter than LV-426. Pretty much the same views on the moon. Whichever has a flatter surface

Earth's moon is 3474km in diameter, almost triple that of LV426's alleged 1200km.
1200km is seriously tiny. As in, half the size of Pluto.

As for a gas giant being 10x the size of Jupiter, it's not impossible.

I was going with the other reference that said LV-426 had a diameter of 3,550 km. One site says 1,200, another says 3,550 and another says 12,100km...

If you think a Gas Giant can grow to 10x the size of Jupiter or have a diameter of 1,388,000km than I don't know what to tell you....I've clearly explained to you that it's not possible, it would collapse. You can trust Nasa and the scientific community or you can believe that they do in fact exist. It's your choice of course lol.

[FiorinaFury161]

There are some things that science can not explain, however.

[SiL]

The link clearly states it might be more than one planet or a brown dwarf. Hot Jupiters are physically larger than Jupiter a lot of the time, but have equal or less mass because they're basically overinflated by heat.

[Nostromo]

I see you got that planet from the top of the list from the previous link I posted. Cool.

https://en.m.wikipedia.org/wiki/List_of_largest_exoplanets

That one is 6x Jupiter but read closely what is says. It is a possible brown dwarf star or at the very least a Hot Jupiter. Which means it's closely orbiting its host Star and has been inflated. It would never have gotten that big if it were outside or even in the habitable zone. Calpamos is right outside the habitable zone.

Which makes sense, otherwise they wouldn't even be able to land or explore if it was too close to the host star.

There have been thousands of exoplanets discovered. Only about 5 are more than double the size of Jupiter. All are Hot Jupiters orbiting their stars. A moon next to one of these would not be possible for exploration in the Alien timeline.

There have been hundreds of Gas Giants discovered with 1.1x - 1.8x the size of Jupiter which should easily tell you that that is the maximum size a Gas Giant with explorable moons will be. At least 99.8% of the time.

Also don't confuse mass with size. 2 different things, I'm sure you know this, but can mix them up sometimes.

This is a helpful link as well: https://en.m.wikipedia.org/wiki/List_of_exoplanets

There have been roughly 3,500 exoplanets found.

If you sort them by Jupiter Radius size...you can clearly see that there's nothing much bigger than 2x Jupiter.

Last thing I will say, I am willing to bet the farm that Calpamos is between 80,000 and 180,000 km in diameter...and it's moons between 3,000 and 12,000km. Hopefully they mentiom something in Alien: Covenant.

There are some things that science can not explain, however.

Sure, when you're studying Astronomy, you'll be wise to remember that as there are events and things out there that you may very possibly never comprehend or understand.

But maybe not this one. I really don't think a planet can grow to the size of our Sun.

[Local Trouble]

the gravity of LV-426 (Acheron) is about .86 of Earth's, this hints at a very dense metal core,

This has long been my fanon rationalization as well.  As I've stated over and over, it must have something exotic worth mining or else the company wouldn't bother co-financing a colony there.

[SM]

There's a passing comment to that effect in the novelisation.

[Local Trouble]

Have you written down your knowledge of these things in journals somewhere?

[Engineer]

The simple fact is Acheron can't be as small as the deleted scene says it is because it would be visibly curved when you're standing on it, which it isn't in Alien and it definitely isn't in Aliens.

I don't think that's correct either. I did some snooping around and found some proof, therefore you are guilty of deceiving us lol.

Seriously though, checkout these 2 links, it explains it well enough as do the pictures above and in these links.

Also, our moon is roughly 87km smaller in diameter than LV-426. Pretty much the same views on the moon. Whichever has a flatter surface

Earth's moon is 3474km in diameter, almost triple that of LV426's alleged 1200km.
1200km is seriously tiny. As in, half the size of Pluto.

As for a gas giant being 10x the size of Jupiter, it's not impossible.

I was going with the other reference that said LV-426 had a diameter of 3,550 km. One site says 1,200, another says 3,550 and another says 12,100km...

If you think a Gas Giant can grow to 10x the size of Jupiter or have a diameter of 1,388,000km than I don't know what to tell you....I've clearly explained to you that it's not possible, it would collapse. You can trust Nasa and the scientific community or you can believe that they do in fact exist. It's your choice of course lol.

I'd like to add in a comment to this. I've done a lot of reading on exoplanets and astrophysics, and my understanding is this:

An object is classified as a planet (or dwarf planet, etc...) once it has gained enough mass that it's own gravity crushes it into a roughly spherical shape (other conditions apply as well such as whether it formed in the accretion disk etc...). Gas giants are different than rocky planets and can ONLY form in the frost region which is far enough away that gases can coalesce into a single object (which you mentioned before). Moving up from gas giants...

An object is classified as a brown dwarf once it has gained enough mass that it's own gravity crushes atoms together at the core creating fusion HOWEVER fusion is not sustained and may only last a couple thousand years or so. Once fusion stops, the object behaves more like a large planet. Young brown dwarfs are often mistaken for small stars, and old brown dwarfs are often mistaken as large planets. Technically, brown dwarfs are their own thing; a transitional step between gas giant planets and the next object up...

An object is classified as a star once it has gained enough mass that gravity creates and sustains fusion.

Fusion generates an outward force that counteracts the crushing force of gravity, creating an equilibrium that prevents the star from collapsing in on itself. Hydrogen is the easiest atom to fuse, and is consumed first in a star's life cycle. When two hydrogens fuse you get helium. At some point, the primary fuel for the star switches from hydrogen fusion to helium fusion, and helium fusion generates less energy than hydrogen fusion. This process continues up the periodic table of elements until you hit iron (the star killer). When iron is created, it consumes energy rather than releases energy, and the star loses that outward force that counteracted gravity, thus causing the star to collapse in on itself. This collapse will result in one of two outcomes depending on how massive the star was to begin with: either a supernova which leaves behind a pulsar, or a stellar-mass black hole. This is a very simplified explanation; there are a lot more details and some slight differences in how this process works depending on how massive the star is/was, but this is the gist of it, which brings me to my main point/contribution...

Gas giant planets won't collapse or implode if they gain too much mass. They'll transition up to the next object type. If that object happens to be a star, the star will need to burn through its fuel source for millions of years before it reaches the point of collapse/implosion. And similarly, pulsars 'theoretically' have a life cycle of their own which lasts millions of years, but instead of fusing atoms it's fusing protons and electrons to create neutrons (hence the alternative name neutron star), until eventually the pulsar runs out of fuel and transitions into a theoretical (and never observed) quark star (aka strange star). Quark stars fuse quarks together and are theorized to be the transitional step between pulsars and smaller stellar-mass black holes. Ok now I'm rambling. Anyway... Yea, lots of mass needed to cause a collapse, and you'd be in  the star size range at that point.

The 'planet' referenced before, HD 100546 b, is VERY massive and has a large diameter. It's radius is approximately 6x that of jupiter's, and it's mass is approximately 17.5x jupiter's. Depending on your source, they may refer to this as a planet. I have this nifty app on my iPhone called "exoplanets" (which I'd recommend) which classifies this as a planet. However it IS actually believed to be a brown dwarf or possibly two planets in close proximity. Similarly, the exoplanet "DENIS-P J082303.1-491201 b" is 30x the mass of Jupiter, and some sources list it as a "planet" while others call it a "brown dwarf." It seems like a lot of resources use the terms 'planet' and 'brown dwarf' interchangeably, which is not technically correct.

That's all mass-based information though. You also mentioned size, or diameter. That matters very little; it just changes the planet's density, really, which you described accurately. Did you know that if you had a tub of water large enough, Saturn would float? It's massive, but it's also highly inflated giving it a very low density. Most highly inflated gas giants observed are classified as hot jupiters, which are close to their host star and the heat causes the inflation. But they cannot form that close to the star; they have to form in the frost region and migrate inwards. And once they become a hot Jupiter they don't last too long; the star is essentially boiling the planet's gases away. Most exoplanets discovered have been hot jupiters, which seems to suggest they're the most common type of planet in the universe, but the thing is, that data is likely skewed at the moment. Hot jupiters are the easiest to find; they're large, they orbit close to the host star, etc... And, we've only explored about a fraction of a percentage of the sky for planets. It wasn't until very recently hot jupiters were even realized as possible! We may find, as technology improves, that there are other unique types of gas giants out there too, like over inflated frozen giants or something. How that would work exactly, I don't know, but again no one thought a hot Jupiter was possible 20 years ago.

As for 'calpamos,' I'd say the only safe assumption is that it's not a hot Jupiter... Could be something else, or it could be about the same size and/or mass as Jupiter or Saturn. And it's moons, it's impossible to say their size based on visual reference in the movie. Orbital distance from the planet could vary making one moon look larger than another, and the horizon from the surface view is too skewed from the terrain and atmosphere to see any curvature.

Anyway, that's my take on things...
Sorry for the book. I kinda nerd out on this exoplanet stuff! Lol

PS. Uranus and Neptune are classified as "ice giants" instead of "gas giants" in case anyone is interested... The difference being ice giants are composed of heavier elements than hydrogen and helium (oxygen and nitrogen for example).