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Thread: Astronomy in Disney's latest cartoon

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    Astronomy in Disney's latest cartoon

    For those of you not in the know, Disney has a new animated show out. It's called Amphibia and like a lot of new Disney shows, it's surprisingly dark. It's set on a planet, or other dimension, or something, presumably called Amphibia, that bears a striking resemblence both to Earth in the Carboniferous period, with giant predatory arthropods and amphibians, monstrous plants and endless swamps, and also to the Late Cretaceous period, with its giant toothed birds and primitive mammals. It's a death world and members of the small town the human protagonist finds herself in calmly embrace the possibility that at any moment something might kill them.

    So obviously the astrobiologist in me has been pondering how thick the atmosphere must be, how high the oxygen content etc, but what really struck me was the moon. Whenever it is shown, in whatever situation, it looks like this:

    Presumably a full eclipse while also at last quarter

    I've been pondering how this could work. Perhaps some kind of Trojan relationship?
    "Occam" is the name of the alien race that will enslave us all eventually. And they've got razors for hands. I don't know if that's true but it seems like the simplest answer."

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    Quote Originally Posted by parallaxicality View Post
    For those of you not in the know, Disney has a new animated show out. It's called Amphibia and like a lot of new Disney shows, it's surprisingly dark. It's set on a planet, or other dimension, or something, presumably called Amphibia, that bears a striking resemblence both to Earth in the Carboniferous period, with giant predatory arthropods and amphibians, monstrous plants and endless swamps, and also to the Late Cretaceous period, with its giant toothed birds and primitive mammals. It's a death world and members of the small town the human protagonist finds herself in calmly embrace the possibility that at any moment something might kill them.

    So obviously the astrobiologist in me has been pondering how thick the atmosphere must be, how high the oxygen content etc, but what really struck me was the moon. Whenever it is shown, in whatever situation, it looks like this:

    Presumably a full eclipse while also at last quarter

    I've been pondering how this could work. Perhaps some kind of Trojan relationship?
    That's just earthshine on the dark portion. The only fault I can see if we wish to be technically accurate is that it is darker than the adjoining sky when it would actually be brighter. By the way it's not last quarter but a waning crescent sometime later.

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    I think he's referring to the fact that the lit part looks so red it must be coming through the planet's atmosphere, so must be a total eclipse. But assuming the planet has only one sun, this would never happen at twilight, so we shouldn't look for any true astronomy here!

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    Quote Originally Posted by Ken G View Post
    I think he's referring to the fact that the lit part looks so red it must be coming through the planet's atmosphere, so must be a total eclipse. But assuming the planet has only one sun, this would never happen at twilight, so we shouldn't look for any true astronomy here!
    Or perhaps their sun is a red dwarf.

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    Quote Originally Posted by parallaxicality View Post
    <snip>
    So obviously the astrobiologist in me has been pondering how thick the atmosphere must be, how high the oxygen content etc, but what really struck me was the moon. Whenever it is shown, in whatever situation, it looks like this:

    Presumably a full eclipse while also at last quarter
    I thought what was bothering him was that it ALWAYS looked like a crescent moon.

    And I think the answer is, no matter what the problem is, that this is a cartoon made by people who wouldn't know a crescent moon from a crescent roll.
    At night the stars put on a show for free (Carole King)

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    Quote Originally Posted by Swift View Post
    And I think the answer is, no matter what the problem is, that this is a cartoon made by people who wouldn't know a crescent moon from a crescent roll.
    I'd say it's more likely that the powers-that-be don't think it matters to put thought into it for kids.

    Exec: "What's that thing up here?"
    Animator: "It's their natural satellite. Given the sun is below the horizon, the Moon will be in waning crescent, so it should..."
    Exec: "It's a moon. Make it look like kids think a moon looks like."
    Animator: "But this is a science story for kids, And kids are pretty smar..."
    Exec: "Here's some clipart of a moon. Use this."

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    Quote Originally Posted by DaveC426913 View Post
    Or perhaps their sun is a red dwarf.
    Yes, that would help in more ways than one, not that color ain't important (). But only for a gibbous phase not a crescent one.

    A red dwarf would likely be in tidal lock around the star, thus eliminating the crescent phase view from those on the night side. If the moon is tidally locked, then it would be fixed in its gibbous phase.

    So, if I'm right, the constant use of a phase angle makes sense by the animators, but only for a gibbous phase.
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    Quote Originally Posted by George View Post
    Yes, that would help in more ways than one, not that color ain't important (). But only for a gibbous phase not a crescent one.

    A red dwarf would likely be in tidal lock around the star, thus eliminating the crescent phase view from those on the night side. If the moon is tidally locked, then it would be fixed in its gibbous phase.

    So, if I'm right, the constant use of a phase angle makes sense by the animators, but only for a gibbous phase.
    My bold. The crescent phase would be visible from locations near the planet's terminator, just as here on Planet Earth.

    Come on, you all. In my opinion this is at most a trifling artistic liberty in an animated cartoon feature.

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    Quote Originally Posted by Hornblower View Post
    My bold. The crescent phase would be visible from locations near the planet's terminator, just as here on Planet Earth.
    Oops, what was I thinking? Thanks. If we were to take, say, an M5 MS star and a planet about the size of Earth, to match the Moon's apparent size with this moon (~ 0.5 deg), then it would only be about 185km in diameter and at a distance of ~ 25,500 km (with same orbital period of about 12 hours).

    It looks like this moon would have a very small crescent when at an altitude of about 30 deg, even seen from the terminator. This is due to the much larger apparent size of the star due to the proximity of the planet, which affects the phases.

    Come on, you all. In my opinion this is at most a trifling artistic liberty in an animated cartoon feature.
    Yeah, but it's kinda fun playing with the what ifs.

    [Added: so the answer to the OP is yes, there is a circumstance where the Moon could be stuck in a crescent phase for those seeing it at night, right? ]
    Last edited by George; 2019-Jul-15 at 06:18 PM.
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    We don't need to make the hypothetical star an M dwarf. When I was a kid I saw a crescent Moon look like that on a smoggy evening in Los Angeles, before they started enacting aggressive clean air measures. For this sort of fiction we can make the atmosphere any way we wish.

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    It would make sense; Amphibia certainly has a thicker atmosphere than Earth, because it has insects the size of cows. It would have to have a hugely increased oxygen content, and be far thicker to support the Spitfire-sized dragonflies.
    "Occam" is the name of the alien race that will enslave us all eventually. And they've got razors for hands. I don't know if that's true but it seems like the simplest answer."

    Stephen Colbert.

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    That's pretty obviously not a crescent moon - the red "illuminated" section extends more than halfway around the limb. So it's an albedo feature.
    I'd say you're looking at something in synchronous rotation, with contrasting areas of its surface that are markedly different in colour and reflectivity. How you arrange for that to be continuously illuminated in full phase, I don't know.

    Grant Hutchison

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    Or, I guess, given that the line of demarcation between the red and grey zones appears to be a circular arc, you have a red "moon" suffering permanent partial eclipse from a smaller body (Maybe Amphibia itself? We'd need to see more of the geometry.) That presents the same problem of keeping multiple bodies in a fixed alignment.

    Grant Hutchison

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    Quote Originally Posted by grant hutchison View Post
    Or, I guess, given that the line of demarcation between the red and grey zones appears to be a circular arc, you have a red "moon" suffering permanent partial eclipse from a smaller body (Maybe Amphibia itself? We'd need to see more of the geometry.) That presents the same problem of keeping multiple bodies in a fixed alignment.
    Amphibia eclipsing their moon would make great sense if they would bump its altitude, and it would help explain the redness.

    For an M star host, am I naive to suggest that the moon would likely be tidally locked in a full moon phase position given the closeness of the both planet and moon to the star?

    The color reminds me of your very early post here regarding a T-class star whose photosphere had compounds that restricts the mid-colors, thus producing a crimson color effect. [I was never a color nut until I signed-up with this outfit. ]
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    Quote Originally Posted by Hornblower View Post
    That's just earthshine on the dark portion. The only fault I can see if we wish to be technically accurate is that it is darker than the adjoining sky when it would actually be brighter. By the way it's not last quarter but a waning crescent sometime later.
    Or a waxing crescent, if they happen to be in the planet's version of Australia.
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    Quote Originally Posted by George View Post
    For an M star host, am I naive to suggest that the moon would likely be tidally locked in a full moon phase position given the closeness of the both planet and moon to the star?
    There's no stable gravitational solution to keep three bodies in syzygy, as far as I'm aware.

    Grant Hutchison

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    Quote Originally Posted by grant hutchison View Post
    That's pretty obviously not a crescent moon - the red "illuminated" section extends more than halfway around the limb. So it's an albedo feature.
    I'd say you're looking at something in synchronous rotation, with contrasting areas of its surface that are markedly different in colour and reflectivity. How you arrange for that to be continuously illuminated in full phase, I don't know.

    Grant Hutchison
    My bold. Not necessarily. In naked eye views of our crescent and earthshine phase, the brilliant crescent appears to be enlarged relative to the dark portion. Our vision system is such that the finished perception in the brain is not always geometrically correct. The drawing here is reasonably consistent with what we see.

    After further thought I would be content with letting the lighted portion be naturally red in this fictional setting.

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    Quote Originally Posted by Hornblower View Post
    My bold. Not necessarily. In naked eye views of our crescent and earthshine phase, the brilliant crescent appears to be enlarged relative to the dark portion. Our vision system is such that the finished perception in the brain is not always geometrically correct. The drawing here is reasonably consistent with what we see.
    "Enlarged" is good. But I don't get the illusion that the curve of the horns is extended so that they start to close again, as in the linked image. That looks instead like the crescent on a Turkish flag, which is generated by two circular curves, rather than a semicircle and semi-ellipse.

    Grant Hutchison

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    Quote Originally Posted by grant hutchison View Post
    "Enlarged" is good. But I don't get the illusion that the curve of the horns is extended so that they start to close again, as in the linked image. That looks instead like the crescent on a Turkish flag, which is generated by two circular curves, rather than a semicircle and semi-ellipse.
    Yep....

    Amphibia Moon enlarged.jpg
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    Once again, a trifle in my opinion. The extent of the horns could be an artifact of the artist's perception of the aforementioned illusion. As for the shape of the terminator, the difference between a circular arc and the actual elliptical one is too slight at this phase to be obvious to someone who is not looking for it.

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    Quote Originally Posted by Hornblower View Post
    Once again, a trifle in my opinion. The extent of the horns could be an artifact of the artist's perception of the aforementioned illusion. As for the shape of the terminator, the difference between a circular arc and the actual elliptical one is too slight at this phase to be obvious to someone who is not looking for it.
    Well, that's fine of course.
    I just had the impression folks here were trying to account in detail for the actual appearance of this cartoon object. If we're free to pick what appearances we need to account for, then I guess it's just a red moon that happens to be in the same phase every time it appears in the cartoon, slightly distorted by optical illusion and an unobservant artist.

    Grant Hutchison

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    Quote Originally Posted by Hornblower View Post
    Once again, a trifle in my opinion. The extent of the horns could be an artifact of the artist's perception of the aforementioned illusion. As for the shape of the terminator, the difference between a circular arc and the actual elliptical one is too slight at this phase to be obvious to someone who is not looking for it.
    I take the OP question to be whether or not an exomoon could have a "phase lock" for the planetary observers, such as the one depicted (assumed to be a waning crescent).
    We know time flies, we just can't see its wings.

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    Wow. "phase lock" is a cool term for it.
    "Occam" is the name of the alien race that will enslave us all eventually. And they've got razors for hands. I don't know if that's true but it seems like the simplest answer."

    Stephen Colbert.

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    Quote Originally Posted by grant hutchison View Post
    That's pretty obviously not a crescent moon - the red "illuminated" section extends more than halfway around the limb.
    Our Moon is rare in that it has an angular diameter very close to the sun's, as seen from Earth.

    That is not necessarily the same everywhere else.

    If Amphibia closely orbited a huge dim supergiant, more than 50% of its surface could be in star shine. So it shouldn't be surprising to see a lit crescent that extends more than halfway around the limb.

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    Quote Originally Posted by DaveC426913 View Post
    Our Moon is rare in that it has an angular diameter very close to the sun's, as seen from Earth.

    That is not necessarily the same everywhere else.

    If Amphibia closely orbited a huge dim supergiant, more than 50% of its surface could be in star shine. So it shouldn't be surprising to see a lit crescent that extends more than halfway around the limb.
    Well, the apparent diameter of the moon doesn't matter - only the apparent diameter of the sun in its sky. The terminator is pushed an angular distance into the night side equal to half the apparent diameter of the illuminant - so about a quarter of a degree for the Earth and the moon.
    For a cool star with half the sun's temperature, we'd need to position Amphibia so the star subtended four times the angular diameter of the sun in Earth's sky to give the planet the same temperature as Earth, ceteris paribus. A long way out from a supergiant, and hugged in close for a red dwarf. That would push the terminator into the night side by just a degree. I don't have the necessary tools with me at present to figure what the "real" figure for the cartoon moon is, but I suspect it would have to be more than that to produce the appearance shown. We'd also see a blurred, rather than sharp, terminator if the illuminant was very extended in the sky.

    Grant Hutchison

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    Quote Originally Posted by DaveC426913 View Post
    Our Moon is rare in that it has an angular diameter very close to the sun's, as seen from Earth.

    That is not necessarily the same everywhere else.

    If Amphibia closely orbited a huge dim supergiant, more than 50% of its surface could be in star shine. So it shouldn't be surprising to see a lit crescent that extends more than halfway around the limb.
    Are you the artist? *wink: Because...

    If we use Betelgeuse as an example, then the luminosity increase of ~ 257x that of the Sun would place an earth-like zone to 16AU. At this distance the star would have an apparent disk size of about 23deg, Using my crude art work above for the moon, the necessary apparent size of the star would need to be close to 23 degrees to obtain the extension of the arc illustrated, remarkably.
    We know time flies, we just can't see its wings.

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    Betelgeuse has a bolometric luminosity ~100,000 times that of the Sun. You'll need to move a little farther out, if you're not going to cook the happy little girl in the picture. I think you'll find you're then in the ball-park with my numbers.

    Grant Hutchison
    Last edited by grant hutchison; 2019-Jul-17 at 04:49 PM. Reason: bolometric

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    Quote Originally Posted by George View Post
    Are you the artist? *wink: Because...

    If we use Betelgeuse as an example, then the luminosity increase of ~ 257x that of the Sun would place an earth-like zone to 16AU. At this distance the star would have an apparent disk size of about 23deg, Using my crude art work above for the moon, the necessary apparent size of the star would need to be close to 23 degrees to obtain the extension of the arc illustrated, remarkably.
    My bold. Is that all? From various sources I find upwards of 10,000x, perhaps closer to 100,000 when you include all of the infrared.

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    Quote Originally Posted by grant hutchison View Post
    Well, that's fine of course.
    I just had the impression folks here were trying to account in detail for the actual appearance of this cartoon object. If we're free to pick what appearances we need to account for, then I guess it's just a red moon that happens to be in the same phase every time it appears in the cartoon, slightly distorted by optical illusion and an unobservant artist.

    Grant Hutchison
    I would not necessarily infer that the artist was unobservant. He or she might have been very observant of the Turkish flag and of the aforementioned naked eye illusion with the real Moon.

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    Quote Originally Posted by grant hutchison View Post
    Betelgeuse has a bolometric luminosity ~100,000 times that of the Sun. You'll need to move a little farther out, if you're not going to cook the happy little girl in the picture. I think you'll find you're then in the ball-park with my numbers.
    Ug! Yes, I rushed my equations.

    For Betelgeuse, at 3500K, R=700X, L increase is 66,000x at 1 AU. Earth equivalent luminosity zone would then be ~ 256 AU. At this distance a Betelgeuse disk would appear as only 1.45 deg.

    Given an Earth-equivalent habitable zone, the size of the star isn't important for determining the apparent size, ironically, but the temperature is. I get about 875K for the surface temperature to produce the desired 23 degrees. [I hope I have at least this right.] Are there post main sequence stars with this low a temperature for their photospheres?

    Added: I suggest this mainly so I don't have to chunk the following ... [The title should have been restated to Inflated Large Star.]
    Attached Images Attached Images
    Last edited by George; 2019-Jul-17 at 05:32 PM.
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