Celestia Forums

Posted: **10.08.2005, 19:06**

Asteroid Sylvia has TWO moons!

http://space.com/scienceastronomy/05081 ... _trio.html

I wonder how many more multiple asteroids are out there?

Posted: **10.08.2005, 19:11**

This is interesting.

Maybe some ssc for Celestia ?

Posted: **10.08.2005, 20:08**

The Singing Badger wrote:Asteroid Sylvia has TWO moons!

http://space.com/scienceastronomy/05081 ... _trio.html

I wonder how many more multiple asteroids are out there?

yes

http://en.wikipedia.org/wiki/87_Sylvia

Remus, the second moon, was announced on August 10, 2005. It was discovered by astronomers at UC Berkeley. It is 7 km in diameter and takes 33 hours to complete an orbit of Sylvia.

Posted: **11.08.2005, 08:03**

here there are the asteroid's data... for ssc file...
http://www.johnstonsarchive.net/astro/a ... 00087.html
for new add-on

very good news!!!

Posted: **11.08.2005, 11:11**

It's not clear what the moon inclination is relative to: asteroid axis or ecliptic... Anyone know?

Spiff.

...OK, it seems its w.r.t the main asteroid Sylvia, and there's a rotation pole solution for it...

Spiff.

Posted: **11.08.2005, 16:16**

Spaceman Spiff wrote:It's not clear what the moon inclination is relative to: asteroid axis or ecliptic... Anyone know?

Spiff.

...OK, it seems its w.r.t the main asteroid Sylvia, and there's a rotation pole solution for it...

Spiff.

...

Code: Select all

"87 Sylvia" "Sol" 
{ 
   Class "asteroid" 
   Texture "asteroid.jpg"
    Mesh  "asteroid.cms"
   Radius  143 # 286 KM diametre => 384 x 264 x 232 km

   EllipticalOrbit 
   { 
   Epoch 2453600.5  #18 Aout 2005
   Period          6.5207
   SemiMajorAxis   3.4902552806
   Eccentricity    0.0796620212
   Inclination     10.85606431
   AscendingNode   73.33018263
   ArgOfPericenter 266.04772538
   MeanAnomaly     53.35606556
   }
   RotationPeriod  5.18365
   Albedo          0.435
}

"S2001_87" "Sol/87 Sylvia" 
{ 
   Class "asteroid" 
   Texture "asteroid.jpg"
    Mesh  "asteroid.cms"
   Radius  18

   EllipticalOrbit 
   { 
   Epoch 2453600.5  #18 Aout 2005
   Period          3.6496 
   SemiMajorAxis   1356
   Eccentricity    0.001
   Inclination     1.7
   LongOfPericenter 0
   AscendingNode    0
   }
   RotationOffset   0
   Albedo  0.2
}

"S2004 87" "Sol/87 Sylvia" 
{ 
   Class "asteroid" 
   Texture "asteroid.jpg"
    Mesh  "asteroid.cms"
   Radius  7

   EllipticalOrbit 
   { 
   Epoch 2453600.5  #18 Aout 2005
   Period          1.3788
   SemiMajorAxis   706
   Eccentricity    0.016 
   Inclination     2.0
   LongOfPericenter 0
   AscendingNode    0
   }
   RotationOffset   0
   Albedo  0.2
}

^^

Posted: **11.08.2005, 17:13**

Excellent stuff!

By the way, Sylvia itself appears to have a long, elliptical shape (see link). Try using the 'bacchus.cmod' mesh instead of the standard 'asteroid.cms' to get this effect.

http://www.eso.org/outreach/press-rel/p ... 21-05.html

Posted: **11.08.2005, 18:43**

Hi symaski62, here's my effort. Care to compare? I too could not find ArgOfPericenter, AscendingNode or MeanLongitude data for the moons. The first two would be unimportant because of low orbit inclination, but maybe we could extract the third from somewhere?

I've managed to include the rotation orientation of the main asteroid, which sets up the orbits of the moons to a proper orientation too... I think. At least, it's been a lot of calculations and 3D imagining, but I think I've got the north pole pointed at the right place.

I've left the main asteroid mesh as the usual 'asteroid.cms'. I think the ESO photo reminds me more of Eros than Bacchus...

Spiff.

Code: Select all

"87 Sylvia" "Sol"
# Pole Solution: Lambda (72.4?±0.5)?° Beta (62.6?±0.5)?°, relative to ecliptic, J2000.0
#                R.A. 19.5?° Dec. +81.5?°.
{
  Class "asteroid"
  EllipticalOrbit
  {
    Epoch 2453600.5 # 18.0 Aug 2005. 
    Period 6.5207 
    SemiMajorAxis 3.4902552806 
    Eccentricity 0.0796620212 
    Inclination  10.85606431 
    AscendingNode 73.33018263 
    ArgOfPericenter 266.04772538 
    MeanAnomaly 53.35606556 
  }
# Mass  # Earth masses. (1.478?±0.006)?—10^19 kg.
  Radius 143 # Mean. Dimensions 384?—264?—232.
  Mesh "asteroid.cms"
  EquatorAscendingNode 182.49 # TBC. See Pole Solution.
  Obliquity 29.2 # TBC. See Pole Solution.
  RotationPeriod 5.18365 
  Albedo 0.0435 
  Texture "asteroid.jpg"
}

"S/2001 (87) 1 (Romulus)" "Sol/87 Sylvia"
{
  Class "asteroid"
  EllipticalOrbit
  {
    Epoch 2453600.5 # 18.0 Aug 2005.
    Period 3.6496 # ?± 0.0007.
    SemiMajorAxis 1356 # ?± 5.
    Eccentricity 0.001 # ?± 0.001.
    Inclination  1.7 # ?± 1.0.
    AscendingNode 0.0 # TBD.
    ArgOfPericenter 0.0 # TBD.
    MeanAnomaly 0.0 # TBD.
  }
# Mass  # Earth masses. TBD kg.
  Radius 9 # ?± 2. Mean.
  Albedo 0.0435 # TBD. Leave as for 87 Sylvia.
  Mesh "asteroid.cms"
  RotationPeriod 87.5904 # ?± 0.0168. TBD. Leave as synchronous 1:1.
  Texture "asteroid.jpg"
}

"S/2001 (87) 2 (Remus)" "Sol/87 Sylvia"
{
  Class "asteroid"
  EllipticalOrbit
  {
    Epoch 2453600.5 # 18.0 Aug 2005.
    Period 1.3788 # ?± 0.0007.
    SemiMajorAxis 706 # ?± 5.
    Eccentricity 0.016 # ?± 0.011.
    Inclination  2.0 # ?± 1.0.
    AscendingNode 0.0 # TBD.
    ArgOfPericenter 0.0 # TBD.
    MeanAnomaly 0.0 # TBD.
  }
# Mass  # Earth masses. TBD kg.
  Radius 3.5 # ?± 1. Mean.
  Albedo 0.0435 # TBD. Leave as for 87 Sylvia.
  Mesh "asteroid.cms"
  RotationPeriod 33.0912 # ?± 0.0168. TBD. Leave as synchronous 1:1.
  Texture "asteroid.jpg"
}

Posted: **11.08.2005, 23:57**

OK ! thanks

Posted: **12.08.2005, 07:54**

Well, if anyone can tell the pole and orbits are not aligned properly, let me know!

Spiff.

Posted: **18.08.2005, 21:39**

Sylvia, Romulus and Remus make it onto APOD :-
http://antwrp.gsfc.nasa.gov/apod/ap050818.html

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Triple asteroid discovered!!

Triple asteroid discovered!!

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