new moon orbits Pluto

[kristoffer]

It is been found a new moon around Pluto
http://www.space.com/12356-pluto-fourth ... photo.html

[Reiko]

Exciting!

[CAP-Team]

Here's an add-on.
The elements come from the Horizons system.

Code: Select all

"Pluto IV" "Sol/Pluto"
{
  Class            "moon"
  Texture          "asteroid.jpg"      # "spectrally neutral"
  Mesh             "asteroid.cms"
  Radius                  17
  Albedo                   0.18

  OrbitFrame { EclipticJ2000 { Center "Sol/Pluto_bary"}}

  EllipticalOrbit {
    Epoch            2457217.500000000       # A.D. 2015-Jul-14 00:00:00.000
    Eccentricity           0.44094759511847  # Eccentricity
    Inclination          179.93189906228     # Inclination (degrees)
    SemiMajorAxis     103412.98367567        # Semi-major Axis (AU)
    ArgOfPericenter      107.30665208468     # Argument of Pericenter (degrees)
    AscendingNode        277.13609331269     # Ascending Node (degrees)
    MeanAnomaly            6.3491343277713   # Mean Anomaly (Position of body at epoch, degrees from pericenter angle)
    Period                81.842389838233    # Period in earth days
  }
}


[Marco Klunder]

Here's an add-on.

Indeed an exiting discovery... and thanks for the add-on... but...

I must say, isn't the upcoming Hydra-P4 encounter (using this add-on) on 18 Sep 2011 a bit too close
Only 7782,6 km

P4_Hydra encounter.jpg

And on 7 Dec 2011 only 1776,2 km


The add-on also suggest a retrograde motion of P4, instead of the NASA picture below:

compass-scale-image-pluto.jpg

The add-on also shows P4 in the neighbourhood of Hydra on 28-Jun and 3-Jul, while the Hubble Telescopy image says it's in the neighbourhood of Nix!
But looking closer at the Celestia representation of the Complete Pluto System, that might not be a specific Add-on issue but a Celestia (minormoon) implementation bug..., because I cannot reproduce a Hubble like picture at all during these 2 dates:

pluto-satellite-system-28Jun.jpg

PS. Suggest to change class as "minormoon" instead of "moon" in the Add-on.

Marco

[ajtribick]

Orbit looks wrong to me.

Running the Horizons for P4 w.r.t the Pluto system barycentre, I get an eccentricity of about 0.02, rather than the high-eccentricity orbit you've got here.

[CAP-Team]

My parameters in the Horizons system were wrong.

Here are the updated elements, for epoche 2011-06-28

Code: Select all

  EllipticalOrbit {
    Epoch            2455740.500000000       # A.D. 2011-Jun-28 00:00:00.000
    Eccentricity           0.019157172981776 # Eccentricity
    Inclination          112.80279383693     # Inclination (degrees)
    SemiMajorAxis      56247.755167425       # Semi-major Axis (km)
    ArgOfPericenter      257.2177965294      # Argument of Pericenter (degrees)
    AscendingNode        227.42287453946     # Ascending Node (degrees)
    MeanAnomaly          180                 # Mean Anomaly (Position of body at epoch, degrees from pericenter angle)
    Period                30.96395634409     # Period in earth days
  }


I can now reproduce Hubble's image:

[Marco Klunder]

Hello,

Implementing the new parameters by CAP-team indeed gives a better picture, however I also needed to change:

Code: Select all

OrbitFrame { EclipticJ2000 { Center "Sol/Pluto_bary"}}

to

Code: Select all

OrbitFrame { EclipticJ2000 { Center "Sol/Pluto-Charon"}}

to prevent the orbit of P4 being drawn with a big angle relative to the other orbits and not being labled.

Wrong angle.jpg

Here's my result with the changed code above, according to the Hydra and Nix definitions in numberedmoons.ssc:

pluto-satellite-system-28Jun.jpg

So the orbits are looking good, as well as the position of Charon an P4 compared to the Hubble image and compared to the image by CAP-team.
The positions of Nix and Hydra however do certainly not match.
Knowing this has nothing to do with the P4 add-on, but what's going wrong here
Nix and Hydra in CAP-teams picture are drawn at other postitions, indeed corresponding to the Hubble image, but not on my system...

Im using the default settings for these minor moons (numberedmoons.ssc) and tested with v1.6.1 and SVN....

Marco

[CAP-Team]

Marco, that's why I'm using spice kernels for most moons and all planets.
This way, you get the most accurate positions possible.
Downside is that Celestia won't run as smooth as with calculated or VSOP orbits.

[chris]

JPL has already got a SPICE kernel with the orbit of P4:

ftp://naif.jpl.nasa.gov/pub/naif/generi ... atellites/

The relevant file is plu020.bsp and it covers the orbit of P4 from 2005 through the beginning of 2016.

--Chris

[John Van Vliet]

--- edit ---

[symaski62]

Ephemeris Type [change] : ELEMENTS
Target Body [change] : [904]
Center [change] : Pluto (body center) [500@999]
Time Span [change] : Start=2011-08-04, Stop=2011-08-14, Step=1 d
Table Settings [change] : output units=KM-D
Display/Output [change] : default (formatted HTML)

Code: Select all

Revised: Jul 21, 2011   S/2011 (134340) 1 / Pluto                        904

 Fit to all available observations of newly discovered satellite of Pluto
 reported in CBAT 2769 (Jul 20, 2011).

 Diameter depends on the assumed geometric albedo:
   14 km if p_v = 0.35, or 40 km if p_v = 0.04.

 Motion is consistent with a body traveling on a circular, equatorial orbit.

 Inferred mean motion is 11.2 +/- 0.1 degrees per day (P = 32.1 +/- 0.3 days),
 and the projected radial distance from Pluto is 59000 +/- 2000 km, placing
 the satellite between the orbits of Pluto II (Nix) and III (Hydra).

 Prediscovery measurements provide a data arc spanning 2006-2011.

Ephemeris Type [change] : VECTORS
Target Body [change] : [904]
Coordinate Origin [change] : Pluto System Barycenter [500@9]
Time Span [change] : Start=2011-08-04, Stop=2011-10-03, Step=1 h
Table Settings [change] : output units=KM-S; quantities code=2; CSV format=YES; object page=NO
Display/Output [change] : default (formatted HTML)

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"P4:pluto 4" "Sol/Pluto-Charon"
{
    Class "moon"
   Radius 20


    BodyFrame {
        EclipticJ2000 { Center "Sol/Pluto-Charon" }
    }
   
   OrbitFrame {
      EclipticJ2000 { Center "Sol/Pluto-Charon" }
   }
   
   SampledTrajectory { Source "test2.xyzv" }
   
   Albedo 0.18
}

[symaski62]

Ephemeris Type [change] : ELEMENTS
Target Body [change] : [904]
Center [change] : Pluto System Barycenter [500@9]
Time Span [change] : Start=2011-08-04, Stop=2011-10-03, Step=1 h
Table Settings [change] : output units=KM-D
Display/Output [change] : default (formatted HTML)

Code: Select all

"Pluto IV" "Sol/Pluto-Charon"
{
  Class            "moon"
  Texture          "asteroid.jpg"      # "spectrally neutral"
  Mesh             "asteroid.cms"
  Radius                  20
  Albedo                   0.18

    BodyFrame {
        EclipticJ2000 { Center "Sol/Pluto-Charon" }
    }
   
   OrbitFrame {
      EclipticJ2000 { Center "Sol/Pluto-Charon" }
   }

  EllipticalOrbit {
    Epoch                  2455777.500000000   # A.D. 2011-Aug-04 00:00:00.0000 (CT)
    Eccentricity            0.001915717298180381 # Eccentricity
    Inclination              112.8027938369342 # Inclination (degrees)
    SemiMajorAxis           56247.75516742301 # Semi-major Axis (KM)
    ArgOfPericenter          311.2992131029849 # Argument of Pericenter (degrees)
    AscendingNode          227.4228745394583   # Ascending Node (degrees)
    MeanAnomaly             180.0000000000114 # Mean Anomaly (Position of body at epoch, degrees from pericenter angle)
    Period                 30.96395634408879 # Period in earth days
  }
}

[John Van Vliet]

--- edit ---

[chris]

still testing but running the spice kernel "plu017xl.bsp" and "plu20.bsp"
a shot for
Jun 28 23:0:0 UTC
compare to the Hubble image above

and p4 is in a bit of a different orbital plane
pluto,Charon,nix,hydra are in one with the barycenter
and p4 is by it's self

I don't think that this is correct: P4 should be in the same plane as the other satellites. In your image, the angle between the orbital planes of P4 and the other satellites looks suspiciously close to 23 degrees, which suggests a mixup of equatorial and ecliptic frames.

--Chris

[John Van Vliet]

--- edit ---

[Tegmine]

All this fuss, and Pluto still isn't considered a "proper" planet?

-M-

[Hungry4info]

A planet must:

1) Orbit a star.
2) Have sufficient mass to achieve hydrostatic equilibrium.
3) Gravitationally dominate the neighbourhood around its orbit.

The number of moons is irrelevant. You may as well ask why the sun isn't considered a planet based on the criteria of number of orbiting bodies.

[W0RLDBUILDER]

Guys, let's not start a flame war. We all know it's a planet anyway. Anyway, about the moon, I already have a mesh in the works. Of course it's fictional, we know next to nothing about P4's shape (or that of Nix or Hydra, for that matter).

[John Van Vliet]

--- edit ---

[Cham]

John,

what about giving the model itself here, so we can try it ? (high res, please).

EDIT : According to your YouTube video, there's a nasty line visible on the model, and even a hole on a pole ?