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## TRAPPIST-1 system: 7 Earth-sized planets

Description: General physics and astronomy discussions not directly related to Celestia

selden
selden
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Whoa, selden you are a genius! Thanks!!!
Not really. This is one of the examples provided in the Celestia WikiBook at https://en.wikibooks.org/wiki/Celestia/Reference_Frames#Sun-locked

how can I rotate a little bit the tidally locked planet? It's texture is not at the right spot...(I don't want to manipulate the texture).

One way to do it is to define a separate viewable object which is rotated by the appropriate amount and positioned relative to the one that's phase-locked to the primary.

For example, change the name of the original object from "b" to "b0" and reduce its size (so it'll be hidden), then define "b" relative to it with an appropriate MeridianAngle. There's an example of this on the WikiBook page linked above. A disadvantage of this method is that b's orbit is no longer drawn since it's in a fixed location.

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`"b0" "TRAPPIST-1"{Class "planet"Radius 1EllipticalOrbit {Period 0.004136538836 #1 year = 365.25 daySemiMajorAxis 0.01111Eccentricity 0.081Inclination 89.65}}Modify "b0" "Trappist-1"{BodyFrame {    TwoVector {        Center "Trappist-1/b0"        Primary {            Axis "z"            RelativePosition { Target "Trappist-1" }        }        Secondary {            Axis "x"            RelativeVelocity { Target "Trappist-1" }        }    }  }}"b" "TRAPPIST-1"{   Mass 0.85 #Radius 6918.906 #earth 1 = 6371 kmTexture "amalthea.*"  OrbitFrame { BodyFixed { Center "Trappist-1/b0" }}  FixedPosition  [ 0 0 0 ]  BodyFrame { BodyFixed { Center  "Trappist-1/b0" }}  FixedRotation { MeridianAngle 25 }}`
Selden

john71
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john71
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Thanks anyway, and you are a genius, because nobody helped me as much as you did in the last few months.

Anyway I made a PDF file from the book...
Celestia online book.pdf.zip

Added after 10 minutes 39 seconds:
TRAPPIST-1 is an exciting star system...not only for us....

http://forum.celestialmatters.org/viewtopic.php?f=17&t=828&start=45

It would be fantastic to make an accurate add-on for Celestia. I will try to make "original" surface, specular and bump textures for each planet in 8k resolution, but getting the orbital data right is a problem for me right now...

selden
selden
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Location: NY, USA
Here's a revised use of the "dual planet" technique which does show an orbital path associated with the revised planet:
define the initial planet as Class "invisible" and use exactly the same orbit definition for the second, visible, planet.

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`"b0" "TRAPPIST-1"{   Radius 1   Class "invisible"EllipticalOrbit {Period 0.004136538836 #1 year = 365.25 daySemiMajorAxis 0.01111Eccentricity 0.081Inclination 89.65}}Modify "b0" "Trappist-1"{BodyFrame {    TwoVector {        Center "Trappist-1/b0"        Primary {            Axis "z"            RelativePosition { Target "Trappist-1" }        }        Secondary {            Axis "x"            RelativeVelocity { Target "Trappist-1" }        }    }  }}"b" "TRAPPIST-1"{   Mass 0.85 #Radius 6918.906 #earth 1 = 6371 kmTexture "amalthea.*"EllipticalOrbit {Period 0.004136538836 #1 year = 365.25 daySemiMajorAxis 0.01111Eccentricity 0.081Inclination 89.65}  BodyFrame { BodyFixed { Center  "Trappist-1/b0" }}  FixedRotation { MeridianAngle 45 Inclination 45 }}`
Selden

john71
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john71
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Selden, thank you very much, I will try it tomorrow!

Meantime I found another solution:

FixedRotation { Inclination -90 AscendingNode 90 }

This moves the texture to the right place...

3 new pictures:

john71
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john71
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TRAPPIST-1f, e, d, c, b, the first five planets (still working on them, just a preview):

Added after 1 minute 16 seconds:
TRAPPIST-1g and TRAPPIST-1h:

ajtribick
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I agree it is somewhat difficult to get the orbital elements right, particularly when most of the cases you are likely to come across are wrong. Nevertheless I do find it slightly surprising that almost no-one seems to check whether the transiting planets in their add-ons actually transit the star from the correct viewing direction.

If you don't want to do the transform, you could try a two vector frame with the first axis being the z-axis pointing towards the Sun, and the x-axis towards north in the equatorial system (but watch out for the correct interpretation of radial coordinates!). I prefer to do the transform to ecliptic coordinates (easier to do once you've converted from Euler angles to a representation of rotation that's easier to manipulate, e.g. quaternions) because reference frames don't work in .stc files and I like to be able to deal with binary stars properly.

john71
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john71
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I reworked TRAPPIST-1g (I don't really understand NASA's depiction of this planet. If there are oceans and it is (maybe) habitable, then why are there clouds like on
Neptune?) I mean it is tidally locked, it must have large ice fields...and must have warmer oceans on one side. It must be similar to TRAPPIST-1f.

Added after 16 minutes 54 seconds:
TRAPPIST-1d is also an interesting planet. Not habitable, but it has liquid water on it...maybe "seas"...a closeup picture:

Reworked TRAPPIST-1e and f:

john71
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john71
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TRAPPIST-1f with fused and mixed
c.) generated Earth-like surface
d.) real Earth bump
textures.

john71
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john71
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OK, the last few pictures: TRAPPIST-1e (I decided to erase all ice fields from the surface) and TRAPPIST-1g, a green ice planet with some liquid water on it's surface (I used Europa bump map textures).

Age: 34
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https://arxiv.org/abs/1703.04166

36 pages

18.764 days
SemiMajorAxis 0.059
Epoch 2457662.55482

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`"h" "TRAPPIST-1"{   Radius 4555  # radius of 0.715 Earth radii   Mass 0.377359 # from mass-radius relationship   Texture "asteroid.*"   EllipticalOrbit {      SemiMajorAxis 0.059        Period 0.05137303217 # 18.764 days      Eccentricity 0      Epoch 2457662.554482 # transit midpoint      MeanAnomaly 90.000      ArgOfPericenter 180.000 # unknown, 0 assumed      Inclination 0.834      AscendingNode 255.734 # unknown, using ecliptic   }   UniformRotation {      Inclination 0.834 # to match orbit      AscendingNode 255.734 # to match orbit   }}`
vista home basic
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with a general handicap of 80% and it makes much d' efforts for the community and s' expimer, thank you d' to be understanding.

john71
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john71
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Thank you for the information!

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https://arxiv.org/abs/1704.02261

Plausible Compositions of the Seven TRAPPIST-1 Planets Using Long-term Dynamical Simulations

TRAPPIST-1 is a nearby ultra-cool dwarf that is host to a remarkable planetary system consisting of seven transiting planets.

Here we perform many thousands of N-body dynamical simulations with planet properties perturbed from the observed values and identify those that are stable for millions of years. This allows us to identify self-consistent orbital solutions that can be used in future studies. From our range of dynamical masses, we find that most of the planets are consistent with an Earth-like composition, where TRAPPIST-1f is likely to have a volatile-rich envelope.
vista home basic
intel(R) Pentium(R) Dual CPU E2160 @ 1,80GHz 1,79GHz
1Go RAM
NVIDIA GeForce 8400 GS
directX 11
celestia 1.6
with a general handicap of 80% and it makes much d' efforts for the community and s' expimer, thank you d' to be understanding.

john71
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john71
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That's interesting. So it hasn't got a stable orbit and if it is not stable, there is a much less chance of habitability...

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