TRAPPIST-1 system: 7 Earth-sized planets

[john71]

NASA has just announced that in the TRAPPIST-1 system there are 7 Earth-sized planets and 3 of them are in the habitable zone.

Source: NASA website + http://www.trappist.one/#

TRAPPIST-1A - the star
Name 2MASS J23062928-0502285
Alternate name TRAPPIST-1
Right ascension α = 23h 06m 29.28s
Declination δ = -05º 02' 28.5''
Constellation Aquarius
Apparent magnitudes V = 18.80 ± 0.08, R = 16.47 ± 0.07,
I=14.0 ± 0.1, J = 11.35 ± 0.02, K = 10.30 ± 0.02
Parallax 82.58 ± 2.58 mas
Distance 12.1 ± 0.4 pc
Mass 0.080 ± 0.007 M☉
Radius 0.117 ± 0.004 R☉
Density 50.7 -2.2+1.2 ρ☉
Effective temperature 2559 ± 50 K
Luminosity 0.000525 ± 0.000036 L☉
Metallicity [Fe/H] +0.04 ± 0.08
Age > 500 Myr

TRAPPIST-1b
Orbital period 1.51087081 ± 0.00000060 days
Mid-transit time 2 457 322.51736 ± 0.00010 (Julian Date)
Transit depth 0.7266 ± 0.0088
Scale parameter (a/R★) 20.50 -0.16+0.31
Impact parameter 0.126 ± 0.085 R☉
Transit duration 36.40 ± 0.17 minutes
Orbital inclination 89.65 ± 0.25º
Orbital eccentricity < 0.081
Semi-major axis 0.01111 ± 0.00034 AU
Radius 1.086 ± 0.035 R⊕
Mass 0.85 ± 0.72 M⊕
Density 0.66 ± 0.56 ρ⊕
Irradiation 4.25 ± 0.33 S⊕
Equilibrium temperature (A=0) 400.1 ± 7.7 K

TRAPPIST-1c
Orbital period 2.4218233 ± 0.0000017 days
Mid-transit time 2 457 282.80728 ± 0.00019 (Julian Date)
Transit depth 0.687 ± 0.010
Scale parameter (a/R★) 28.08 -0.42+0.22
Impact parameter 0.161 ± 0.080 R☉
Transit duration 42.37 ± 0.22 minutes
Orbital inclination 89.67 ± 0.17º
Orbital eccentricity < 0.083
Semi-major axis 0.01521 ± 0.00047 AU
Radius 1.056 ± 0.035 R⊕
Mass 1.38 ± 0.61 M⊕
Density 1.17 ± 0.53 ρ⊕
Irradiation 2.27 ± 0.18 S⊕
Equilibrium temperature (A=0) 341.9 ± 6.6 K

TRAPPIST-1d
Orbital period 4.049610 ± 0.000063 days
Mid-transit time 2 457 670.14165 ± 0.00035 (Julian Date)
Transit depth 0.367 ± 0.017
Scale parameter (a/R★) 39.55 -0.59+0.30
Impact parameter 0.17 ± 0.11 R☉
Transit duration 49.13 ± 0.65 minutes
Orbital inclination 89.75 ± 0.16º
Orbital eccentricity < 0.070
Semi-major axis 0.02144 ± 0.00065 AU
Radius 0.772 ± 0.030 R⊕
Mass 0.41 ± 0.27 M⊕
Density 0.89 ± 0.60 ρ⊕
Irradiation 1.143 ± 0.088 S⊕
Equilibrium temperature (A=0) 288.0 ± 5.6 K

TRAPPIST-1e
Orbital period 6.099615 ± 0.000011 days
Mid-transit time 2 457 660.37859 ± 0.00035 (Julian Date)
Transit depth 0.519 ± 0.026
Scale parameter (a/R★) 51.97 -0.77+0.40
Impact parameter 0.12 ± 0.10 R☉
Transit duration 57.21 ± 0.71 minutes
Orbital inclination 89.86 ± 0.11º
Orbital eccentricity < 0.085
Semi-major axis 0.02817 ± 0.00085 AU
Radius 0.918 ± 0.039 R⊕
Mass 0.62 ± 0.58 M⊕
Density 0.80 ± 0.76 ρ⊕
Irradiation 0.662 ± 0.051 S⊕
Equilibrium temperature (A=0) 251.3 ± 4.9 K

TRAPPIST-1f
Orbital period 9.206690 ± 0.000015 days
Mid-transit time 2 457 671.39767 ± 0.00023 (Julian Date)
Transit depth 0.673 ± 0.023
Scale parameter (a/R★) 68.4 -1.0+0.5
Impact parameter 0.382 ± 0.035 R☉
Transit duration 62.60 ± 0.60 minutes
Orbital inclination 89.680 ± 0.034º
Orbital eccentricity < 0.063
Semi-major axis 0.0371 ± 0.0011 AU
Radius 1.045 ± 0.038 R⊕
Mass 0.68 ± 0.18 M⊕
Density 0.60 ± 0.17 ρ⊕
Irradiation 0.382 ± 0.030 S⊕
Equilibrium temperature (A=0) 219.0 ± 4.2 K

TRAPPIST-1g
Orbital period 12.35294 ± 0.00012 days
Mid-transit time 2 457 665.34937 ± 0.00021 (Julian Date)
Transit depth 0.782 ± 0.027
Scale parameter (a/R★) 83.2 -1.2+0.6
Impact parameter 0.421 ± 0.031 R☉
Transit duration 68.40 ± 0.66 minutes
Orbital inclination 89.710 ± 0.025º
Orbital eccentricity < 0.061
Semi-major axis 0.0451 ± 0.0014 AU
Radius 1.127 ± 0.041 R⊕
Mass 1.34 ± 0.88 M⊕
Density 0.94 ± 0.63 ρ⊕
Irradiation 0.258 ± 0.020 S⊕
Equilibrium temperature (A=0) 198.6 ± 3.8 K

TRAPPIST-1h
Orbital period 20 -6+15
Mid-transit time 2 457 662.55463 ± 0.00056 (Julian Date)
Transit depth 0.352 ± 0.033
Scale parameter (a/R★) 117 -26+50
Impact parameter 0.45 ± 0.25 R☉
Transit duration 76.7 ± 2.5 minutes
Orbital inclination 89.80 ± 0.07º
Orbital eccentricity unknown
Semi-major axis 0.063 -0.013+0.027 AU
Radius 0.755 ± 0.034 R⊕
Mass unknown
Density unknown
Irradiation 0.131 -0.067+0.081
Equilibrium temperature (A=0) 168 -28+21 K

TRAPPIST-1x
It is possible that other planets exist around TRAPPIST-1. Further observations may tell us about their presence.

[carton]

why TRAPPIST-1h has unknown mass?

[Cham]

Cool graphics there :

http://www.seeker.com/trappist-1-exoplanets-astro ... ne-star-system-2278551258.html

http://physicsworld.com/cws/article/news/2017/feb ... e-exoplanets-orbit-nearby-star

We need an SSC file, ASAP !

[john71]

I have a version of the TRAPPIST-1 system on Celestia, but with only 3 planets. In a new ssc file the 3 habitable planets should have Earth-like atmospheres...I'm very curious to see the faint star from the surface of the planets...

The "old" TRAPPIST-1 ssc file:

"TRAPPIST-1 b" "TRAPPIST-1"
{
Mass 1.24
Radius 7079.73207
Texture "venuslike.jpg"

EllipticalOrbit {
Period 0.004134086777493
SemiMajorAxis 0.0111
Eccentricity 0
Inclination 89.4
MeanLongitude 0
}

UniformRotation {
Period 36.24
Inclination 89.4
AscendingNode 0
MeridianAngle 0
}
}

"TRAPPIST-1 c" "TRAPPIST-1"
{
Mass 1.02
Radius 6697.04385
Texture "venuslike.jpg"

EllipticalOrbit {
Period 0.0066254900672405
SemiMajorAxis 0.0152
Eccentricity 0
Inclination 89.5
MeanLongitude 0
}

UniformRotation {
Period 58.08
Inclination 89.5
AscendingNode 0
MeridianAngle 0
}
}

"TRAPPIST-1 d" "TRAPPIST-1"
{
Mass 1.44
Radius 7398.63892
Texture "venuslike.jpg"

EllipticalOrbit {
Period 0.049828065794949
SemiMajorAxis 0.0583
Eccentricity 0
Inclination 89.9
MeanLongitude 0
}

UniformRotation {
Period 436.8
Inclination 89.9
AscendingNode 0
MeridianAngle 0
}
}

[Cham]

I'm not home right now, so I don't have access to my Celestia. I think I have an SSC file for 3 planets around this star, like you.

[selden]

A complete SSC for the system is available on CelestialMatters. Unfortunately, it uses unit designations which are available only if you compile Celestia from source code. They aren't supported by Celestia v1.6.1. Perhaps someone could take the time to translate it into something which is compatible.

See http://forum.celestialmatters.org/viewtopic.php?f ... 9ae6bc64e637421d4dc5e5d#p14674

[Cham]

If some are using a Mac, the special version published here could be used. Andrew's file with units is working great !

viewtopic.php?f=4&t=17423

Preview :

[john71]

Selden, thanks! By the way it is very simple to translate them, you just have to use Notepad++ or something similar. The <...> functions were the problem. I batch deleted them.

Here we go:

"b" "TRAPPIST-1"
{
   Radius 1.09
   Mass 0.85 #

   Texture "exo-class3.*"

   EllipticalOrbit {
      SemiMajorAxis 0.01111
      Period 1.51087
      Eccentricity 0

      Epoch 2457322.517360 # transit midpoint
      MeanAnomaly 90.000

      ArgOfPericenter 180.000 # unknown, 0 assumed
      Inclination 0.984
      AscendingNode 255.734 # unknown, using ecliptic
   }

   UniformRotation {
      Inclination 0.984 # to match orbit
      AscendingNode 255.734 # to match orbit
   }
}

"c" "TRAPPIST-1"
{
   Radius 1.06
   Mass 1.38 #

   Texture "asteroid.*"

   EllipticalOrbit {
      SemiMajorAxis 0.01521
      Period 2.42182
      Eccentricity 0

      Epoch 2457282.807280 # transit midpoint
      MeanAnomaly 90.000

      ArgOfPericenter 180.000 # unknown, 0 assumed
      Inclination 0.964
      AscendingNode 255.734 # unknown, using ecliptic
   }

   UniformRotation {
      Inclination 0.964 # to match orbit
      AscendingNode 255.734 # to match orbit
   }
}

"d" "TRAPPIST-1"
{
   Radius 0.77
   Mass 0.41 #

   Texture "asteroid.*"

   EllipticalOrbit {
      SemiMajorAxis 0.02144
      Period 4.04961
      Eccentricity 0

      Epoch 2457670.141650 # transit midpoint
      MeanAnomaly 90.000

      ArgOfPericenter 180.000 # unknown, 0 assumed
      Inclination 0.884
      AscendingNode 255.734 # unknown, using ecliptic
   }

   UniformRotation {
      Inclination 0.884 # to match orbit
      AscendingNode 255.734 # to match orbit
   }
}

"e" "TRAPPIST-1"
{
   Radius 0.92
   Mass 0.62 #

   Texture "asteroid.*"

   EllipticalOrbit {
      SemiMajorAxis 0.02817
      Period 6.09962
      Eccentricity 0

      Epoch 2457660.378590 # transit midpoint
      MeanAnomaly 90.000

      ArgOfPericenter 180.000 # unknown, 0 assumed
      Inclination 0.774
      AscendingNode 255.734 # unknown, using ecliptic
   }

   UniformRotation {
      Inclination 0.774 # to match orbit
      AscendingNode 255.734 # to match orbit
   }
}

"f" "TRAPPIST-1"
{
   Radius 1.04
   Mass 0.68 #

   Texture "exo-class3.*"

   EllipticalOrbit {
      SemiMajorAxis 0.0371
      Period 9.20669
      Eccentricity 0

      Epoch 2457671.397670 # transit midpoint
      MeanAnomaly 90.000

      ArgOfPericenter 180.000 # unknown, 0 assumed
      Inclination 0.954
      AscendingNode 255.734 # unknown, using ecliptic
   }

   UniformRotation {
      Inclination 0.954 # to match orbit
      AscendingNode 255.734 # to match orbit
   }
}

"g" "TRAPPIST-1"
{
   Radius 1.13
   Mass 1.34 #

   Texture "asteroid.*"

   EllipticalOrbit {
      SemiMajorAxis 0.0451
      Period 12.3529
      Eccentricity 0

      Epoch 2457665.349370 # transit midpoint
      MeanAnomaly 90.000

      ArgOfPericenter 180.000 # unknown, 0 assumed
      Inclination 0.924
      AscendingNode 255.734 # unknown, using ecliptic
   }

   UniformRotation {
      Inclination 0.924 # to match orbit
      AscendingNode 255.734 # to match orbit
   }
}

"h" "TRAPPIST-1"
{
   Radius 0.76
   Mass 0.377359 # from mass-radius relationship

   Texture "asteroid.*"

   EllipticalOrbit {
      SemiMajorAxis 0.063
      Period 20
      Eccentricity 0

      Epoch 2457662.554630 # 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
   }
}

[selden]

Unfortunately, you can't just delete the unit specifications. Several fields need to have their values changed to correspond to the units that Celestia v1.6.1 uses. For example, the Radius values have to be changed from Earth Radii to Kilometers.

[roninwolf1981]

Will this site work for calculating kilometers from Earth radii?
http://www.conversion-website.com/length/Earth-radius-to-kilometer.html

[john71]

You are right, but at least it "works" in Celestia 1.6...a step in the right direction.

With planets with 1 km radius.

[symaski62]

stc

"TRAPPIST-1"
{
Radius 79344 # 696000 km Rsol = 1
RA 346.622
Dec -5.041275
Distance 12.1
SpectralType "M8V"
AbsMag 18.8
}

ssc

"b" "TRAPPIST-1"
{
Radius 6918.906 #earth 1 = 6371 km

EllipticalOrbit {
Period 0.004136538836 #1 year = 365.25 day
SemiMajorAxis 0.01111
Eccentricity 0.081
Inclination 89.65
}
}

"c" "TRAPPIST-1"
{
Radius 6727.776 #earth 1 = 6371 km

EllipticalOrbit {
Period 0.006630590828 #1 year = 365.25 day
SemiMajorAxis 0.01522
Eccentricity 0.083
Inclination 89.67
}
}

"d" "TRAPPIST-1"
{
Radius 4918.412 #earth 1 = 6371 km

EllipticalOrbit {
Period 0.01108722793 #1 year = 365.25 day
SemiMajorAxis 0.021
Eccentricity 0.070
Inclination 89.75
}
}

"e" "TRAPPIST-1"
{
Radius 5848.578 #earth 1 = 6371 km

EllipticalOrbit {
Period 0.01669983573 #1 year = 365.25 day
SemiMajorAxis 0.028
Eccentricity 0.085
Inclination 89.86
}
}

"f" "TRAPPIST-1"
{
Radius 6657.695 #earth 1 = 6371 km

EllipticalOrbit {
Period 0.02620654346 #1 year = 365.25 day
SemiMajorAxis 0.037
Eccentricity 0.063
Inclination 89.68
}
}

"g" "TRAPPIST-1"
{
Radius 7180.117 #earth 1 = 6371 km

EllipticalOrbit {
Period 0.0338205065 #1 year = 365.25 day
SemiMajorAxis 0.045
Eccentricity 0.061
Inclination 89.71
}
}

"h" "TRAPPIST-1"
{
Radius 4810.105 #earth 1 = 6371 km

EllipticalOrbit {
Period 0.05475701574 #1 year = 365.25 day
SemiMajorAxis 0.063
Eccentricity 0
Inclination 89.80
}
}

[john71]

Yeah! Thanks!!!!!!!

Added after 1 hour 5 minutes:
Work in progress...

"b" "TRAPPIST-1"
{
   Mass 0.85 #
Radius 6918.906 #earth 1 = 6371 km
Texture "amalthea.*"

EllipticalOrbit {
Period 0.004136538836 #1 year = 365.25 day
SemiMajorAxis 0.01111
Eccentricity 0.081
Inclination 89.65
}
}

"c" "TRAPPIST-1"
{
      Mass 1.38 #
   Texture "io.*"
Radius 6727.776 #earth 1 = 6371 km

EllipticalOrbit {
Period 0.006630590828 #1 year = 365.25 day
SemiMajorAxis 0.01522
Eccentricity 0.083
Inclination 89.67
}
}

"d" "TRAPPIST-1"
{
   Mass 0.41 #
 Texture "mars.*"
Radius 4918.412 #earth 1 = 6371 km

EllipticalOrbit {
Period 0.01108722793 #1 year = 365.25 day
SemiMajorAxis 0.021
Eccentricity 0.070
Inclination 89.75
}
}

"e" "TRAPPIST-1"
{
    Mass 0.62 #
   Radius 5848.578 #earth 1 = 6371 km
Texture "earth.*"
SpecularTexture "earth-spec.*"
Color [ 0.85 0.85 1.0 ]
SpecularColor [ 0.8 0.8 0.85 ]
SpecularPower 25.0
HazeColor [ 1 1 1 ]
HazeDensity 0.3
Radius 6378.140 # equatorial

Atmosphere {
Height 60
Lower [ 0.43 0.52 0.65 ]
Upper [ 0.26 0.47 0.84 ]
Sky [ 0.40 0.6 1.0 ]
Sunset [ 1.0 0.6 0.2 ]

CloudHeight 7
CloudSpeed 65
CloudMap "earth-clouds.*"
CloudShadowDepth 1.0

Mie 0.001
MieAsymmetry -0.25
Rayleigh [ 0.001 0.0025 0.006 ]
MieScaleHeight 12
}

EllipticalOrbit {
Period 0.01669983573 #1 year = 365.25 day
SemiMajorAxis 0.028
Eccentricity 0.085
Inclination 89.86
}
}

"f" "TRAPPIST-1"
{
Mass 0.68 #
Radius 6657.695 #earth 1 = 6371 km

Texture "earth.*"
SpecularTexture "earth-spec.*"
Color [ 0.85 0.85 1.0 ]
SpecularColor [ 0.8 0.8 0.85 ]
SpecularPower 25.0
HazeColor [ 1 1 1 ]
HazeDensity 0.3
Radius 6378.140 # equatorial

Atmosphere {
Height 60
Lower [ 0.43 0.52 0.65 ]
Upper [ 0.26 0.47 0.84 ]
Sky [ 0.40 0.6 1.0 ]
Sunset [ 1.0 0.6 0.2 ]

CloudHeight 7
CloudSpeed 65
CloudMap "earth-clouds.*"
CloudShadowDepth 1.0

Mie 0.001
MieAsymmetry -0.25
Rayleigh [ 0.001 0.0025 0.006 ]
MieScaleHeight 12
}

EllipticalOrbit {
Period 0.02620654346 #1 year = 365.25 day
SemiMajorAxis 0.037
Eccentricity 0.063
Inclination 89.68
}
}

"g" "TRAPPIST-1"
{
Mass 1.34 #
Texture "exo-class5.*"
Radius 7180.117 #earth 1 = 6371 km

EllipticalOrbit {
Period 0.0338205065 #1 year = 365.25 day
SemiMajorAxis 0.045
Eccentricity 0.061
Inclination 89.71
}
}

"h" "TRAPPIST-1"
{
   Mass 0.377359 # from mass-radius relationship
   Texture "ganymede.*"
Radius 4810.105 #earth 1 = 6371 km

EllipticalOrbit {
Period 0.05475701574 #1 year = 365.25 day
SemiMajorAxis 0.063
Eccentricity 0
Inclination 89.80
}
}

Added after 1 minute 18 seconds:
By the way, how can I make tidally locked planets?

[roninwolf1981]

I've tried posting something here earlier, but it said it needed admin review, and then my post was never cleared.

[selden]

Normally, if you provide no rotational specifications at all (as is currently the case in the .ssc above), Celestia automatically tide-locks the planet or moon.

Alternatively, you can specify a two-vector body frame.

[john71]

Hmmm..then I don't get it. They are obviously not tidally locked, there is rotation.

Three pictures from TRAPPIST-1e...:

Added after 4 hours 59 minutes:
This is the stc file I use:

"TRAPPIST-1"
{
RA 346.622
Dec -5.041275
Distance 39.46
SpectralType "M8.0V"
Radius 79344
AbsMag 18.4
}

[selden]

That's strange.

Other than setting a rotational period which matches the orbital period (getting them identical is almost impossible, though), the only other way that I'm certain would work would be to use a two-vector body frame. It's not going to be entirely realistic, though, since forces one body axis to always point toward the target and thus doesn't allow any nutation.

For example, add this after the definition of planet "b":

Code: Select all

Modify "b" "Trappist-1"
{
BodyFrame {
    TwoVector {
        Center "Trappist-1/b"
        Primary {
            Axis "z"
            RelativePosition { Target "Trappist-1" }
        }
        Secondary {
            Axis "x"
            RelativeVelocity { Target "Trappist-1" }
        }
    }
  }
}


[john71]

Whoa, selden you are a genius! Thanks!!!

One last question: 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).

[ajtribick]

Posting here because I see this mistake being made time and time again.

Celestia interprets orbital elements as being with respect to the ecliptic plane, while sources typically give them with respect to the sky plane tangent to the star. Plugging the numbers straight into the ssc without doing the transform is the most common mistake in Celestia exoplanet add-ons. I did a quick check of the exoplanet add-ons listed on this page at the Celestia Motherlode, and with only a couple of honourable exceptions they ALL had wrong orbital elements due to not taking the transformation from the sky plane to the ecliptic plane into account.

Getting this right is important if you want to be able to simulate transits properly.

----

On a different subject, Selden is only partially correct about the default rotation. The default rotation period for planets with unspecified rotation periods is the orbital period, this is necessary but not sufficient for simulating a tidally-locked planet. The default direction of the rotation axis and the phase of rotation do not get taken from the orbital elements, so you need to match these in the ssc explicitly.

[john71]

Dear ajtribick, thank you for your post!

As I'm not a scientist would you be so kind to correct one of the orbital elements, step by step?

How can I correct the wrong data?

Added after 12 minutes 35 seconds:
And how can I match default direction of the rotation axis and the phase of rotation in the ssc file?