Hill spheres

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Topic author
Brendan
Posts: 296
Joined: 15.07.2003
With us: 18 years
Location: Bellows Falls, VT
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Hill spheres

Post #1by Brendan » 19.07.2003, 08:18

Hello, I wondered how the sizes of the Hill spheres of the planets would compare so I put them in tiny orbits around the planets. They're white and you could see the planets while inside them if you turn off eclipse shadow rendering.
I got the formula for the Hill sphere radii from Sheppard's paper on the irregular satellites of Jupiter. I wanted to see how close the irregular satellites' orbits came to the surface of Jupiter's Hill sphere.
I guess that I could make the spheres for the major satellites but I would need to figure out how to use the masses of both the planet and sun and the satellite's distances from both of these bodies. It would be nice to see them expanding and contracting as the distances between the satellites, the planet, and sun changed.

Ok, here it is:

Code: Select all

"Mercury Hill Sphere" "Sol/Mercury"
{
   Radius 220605.5

   EllipticalOrbit
   {
      Period 1e-9
      SemiMajorAxis 1e-9
   }
}

"Venus Hill Sphere" "Sol/Venus"
{
   Radius 1010801

   EllipticalOrbit
   {
      Period 1e-9
      SemiMajorAxis 1e-9
   }
}

"Earth Hill Sphere" "Sol/Earth"
{
   Radius 1496083

   EllipticalOrbit
   {
      Period 1e-9
      SemiMajorAxis 1e-9
   }
}

"Mars Hill Sphere" "Sol/Mars"
{
   Radius 1083734

   EllipticalOrbit
   {
      Period 1e-9
      SemiMajorAxis 1e-9
   }
}

"Jupiter Hill Sphere" "Sol/Jupiter"
{
   Radius 53122627

   EllipticalOrbit
   {
      Period 1e-9
      SemiMajorAxis 1e-9
   }
}

"Saturn Hill Sphere" "Sol/Saturn"
{
   Radius 65153536

   EllipticalOrbit
   {
      Period 1e-9
      SemiMajorAxis 1e-9
   }
}

"Uranus Hill Sphere" "Sol/Uranus"
{
   Radius 70013234

   EllipticalOrbit
   {
      Period 1e-9
      SemiMajorAxis 1e-9
   }
}

"Neptune Hill Sphere" "Sol/Neptune"
{
   Radius 1.16e08

   EllipticalOrbit
   {
      Period 1e-9
      SemiMajorAxis 1e-9
   }
}

"Pluto Hill Sphere" "Sol/Pluto-Charon/Pluto"
{
   Radius 7663646

   EllipticalOrbit
   {
      Period 1e-9
      SemiMajorAxis 1e-9
   }
}


Notice that I have Pluto set up to orbit Pluto-Charon, the barycenter. So just take that out if you don't have it. I also noticed that the spheres are not visible unless I got close enough. One of the planet's Hill sphere is really huge (guess which one it is :wink:) yet I can't see it from the inner solar system. Do objects beyond a certain distance from the camera get clipped? I saw that happen when I learned a bit about OpenGL.
This is the first time I posted code to the forum so if I make any mistakes, I'm sorry. :oops:

Brendan

Dan

Post #2by Dan » 21.07.2003, 18:42

Where and in what format do you save it?
*.ssc *.stc *.dsc?


Dan

Topic author
Brendan
Posts: 296
Joined: 15.07.2003
With us: 18 years
Location: Bellows Falls, VT
Contact:

Post #3by Brendan » 23.07.2003, 21:24

Oh, sorry about that. That was the first addon I posted here. It''s a ssc file that I saved as hillspheres.ssc in the extras folder. I also plan on making another addon with the interior structure of the planets, some of the moons and even the sun. I made a new version of the hill sphere file that has the spheres orbiting invisbile bodies at the centers of the planets. This means that the eclipse shadow rendering doesn't need to be turned off to see the planets inside the hill spheres. Should I put the central invisbile bodies in another file? That way, both the hill sphere and the interior files would be able to use them if I name them like centers.ssc, hillsphere.ssc and interior.ssc.

Here's the new hillsphere.ssc that can be put in the extras folder:

Code: Select all

"Mercury Center" "Sol"
{
   Class "invisible"

   CustomOrbit "vsop87-mercury"
   EllipticalOrbit {
   Period            0.2408
   SemiMajorAxis     0.3871
   Eccentricity      0.2056
   Inclination       7.0049
   AscendingNode    48.33167
   LongOfPericenter 77.456
        MeanLongitude   252.251
   }
}

"Mercury Hill Sphere" "Sol/Mercury Center"
{
   Radius 220605.5

   EllipticalOrbit
   {
      Period 1e-9
      SemiMajorAxis 1e-9
   }
}

"Venus Center" "Sol"
{
   Class "invisible"

   CustomOrbit "vsop87-venus"
   EllipticalOrbit {
      Period            0.6152
      SemiMajorAxis     0.7233
      Eccentricity      0.0068
      Inclination       3.3947
      AscendingNode     76.681
      LongOfPericenter 131.533
           MeanLongitude    181.979
   }
}

"Venus Hill Sphere" "Sol/Venus Center"
{
   Radius 1010801

   EllipticalOrbit
   {
      Period 1e-9
      SemiMajorAxis 1e-9
   }
}

"Earth Center" "Sol"
{
   Class "invisible"

   CustomOrbit "vsop87-earth"
   EllipticalOrbit {   
      Period            1.0000
      SemiMajorAxis     1.0000
      Eccentricity      0.0167
      Inclination       0.0001
      AscendingNode   348.739
      LongOfPericenter 102.947
           MeanLongitude   100.464
   }
}

"Earth Hill Sphere" "Sol/Earth Center"
{
   Radius 1496083

   EllipticalOrbit
   {
      Period 1e-9
      SemiMajorAxis 1e-9
   }
}

"Mars Center" "Sol"
{
   Class "invisible"

   CustomOrbit "vsop87-mars"
   EllipticalOrbit
   {
   Period            1.8809
   SemiMajorAxis     1.5237
   Eccentricity      0.0934
   Inclination       1.8506
   AscendingNode     49.479
   LongOfPericenter 336.041
        MeanLongitude    355.453
   }
}

"Mars Hill Sphere" "Sol/Mars Center"
{
   Radius 1083734

   EllipticalOrbit
   {
      Period 1e-9
      SemiMajorAxis 1e-9
   }
}

"Jupiter Center" "Sol"
{
   Class "invisible"

   CustomOrbit "vsop87-jupiter"
   EllipticalOrbit
   {
   Period           11.8622
   SemiMajorAxis     5.2034
   Eccentricity      0.0484
   Inclination       1.3053
   AscendingNode   100.556
   LongOfPericenter 14.7539
        MeanLongitude    34.404
   }
}

"Jupiter Hill Sphere" "Sol/Jupiter Center"
{
   Radius 53122627

   EllipticalOrbit
   {
      Period 1e-9
      SemiMajorAxis 1e-9
   }
}

"Saturn Center" "Sol"
{
   Class "invisible"

   CustomOrbit "vsop87-saturn"
   EllipticalOrbit
   {
   Period           29.4577
   SemiMajorAxis     9.5371
   Eccentricity      0.0542
   Inclination       2.4845
   AscendingNode   113.715
   LongOfPericenter 92.432
        MeanLongitude    49.944
   }
}

"Saturn Hill Sphere" "Sol/Saturn Center"
{
   Radius 65153536

   EllipticalOrbit
   {
      Period 1e-9
      SemiMajorAxis 1e-9
   }
}

"Uranus Center" "Sol"
{
   Class "invisible"

   CustomOrbit "vsop87-uranus"
   EllipticalOrbit
   {
   Period           84.0139
   SemiMajorAxis    19.1913
   Eccentricity      0.0472
   Inclination       0.7699
   AscendingNode     74.230
   LongOfPericenter 170.964
        MeanLongitude    313.232
   }
}

"Uranus Hill Sphere" "Sol/Uranus Center"
{
   Radius 70013234

   EllipticalOrbit
   {
      Period 1e-9
      SemiMajorAxis 1e-9
   }
}

"Neptune Center" "Sol"
{
   Class "invisible"

   CustomOrbit "vsop87-neptune"
   EllipticalOrbit
   {
   Period           164.793
   SemiMajorAxis     30.0690
   Eccentricity      0.0086
   Inclination       1.7692
   AscendingNode   131.722
   LongOfPericenter 44.971
        MeanLongitude   304.880
   }
}

"Neptune Hill Sphere" "Sol/Neptune Center"
{
   Radius 1.16e08

   EllipticalOrbit
   {
      Period 1e-9
      SemiMajorAxis 1e-9
   }
}

"Pluto Center" "Sol/Pluto-Charon"
{
   Class "invisible"

   EllipticalOrbit
   {
   Period           6.387246
   SemiMajorAxis    1499
   Eccentricity     0.0002
   Inclination      115.602
   AscendingNode    228.328
   ArgOfPericenter  47.314
   MeanAnomaly      93.440
   }
}

"Pluto Hill Sphere" "Sol/Pluto-Charon/Pluto Center"
{
   Radius 7663646

   EllipticalOrbit
   {
      Period 1e-9
      SemiMajorAxis 1e-9
   }
}


I copied and pasted the planet orbits from solarsys.ssc to make the centers follow the planets. I have Pluto orbiting the barycenter again.
I'll put the centers in a different file so both the hill spheres and the upcoming interior addon could use them.
I'm wondering if the mantle would cast a shadow on the outer core and the outer core onto the inner core once I add them. They would be orbiting the same invisbile object at the center of the earth. I'll try it and find out.

I'm also wondering if it would be possible to see the planet through the hill sphere if an transparent texture was used or would that only allow other textures, not other objects to be seen under it?

Brendan

Bob Hegwood
Posts: 1048
Joined: 19.10.2003
With us: 17 years 9 months
Location: Germantown, Ohio - USA

Post #4by Bob Hegwood » 14.04.2004, 05:27

Brendan,

Sorry for the intrusion... This is Brain-Dead Bob.

Could you please tell me what a "Hill-Sphere" is? :oops:

Thanks, Bob
Bob Hegwood
Windows XP-SP2, 256Meg 1024x768 Resolution
Intel Celeron 1400 MHz CPU
Intel 82815 Graphics Controller
OpenGL Version: 1.1.2 - Build 4.13.01.3196
Celestia 1.4.0 Pre6 FT1

Topic author
Brendan
Posts: 296
Joined: 15.07.2003
With us: 18 years
Location: Bellows Falls, VT
Contact:

Post #5by Brendan » 14.04.2004, 11:50

http://www.asterism.org/tutorials/tut22-1.htm

I think Grant said some more about this somewhere.

Brendan

Bob Hegwood
Posts: 1048
Joined: 19.10.2003
With us: 17 years 9 months
Location: Germantown, Ohio - USA

Post #6by Bob Hegwood » 14.04.2004, 12:19

Thanks Brendan,

I did understand and enjoy that explanation. :lol:

Take care, Bob

maxim
Posts: 1036
Joined: 13.11.2003
With us: 17 years 8 months
Location: N?rnberg, Germany

Post #7by maxim » 14.04.2004, 13:04

I never heard of the hill sphere model before, but it sounds interesting.

Brendan wrote:I'm also wondering if it would be possible to see the planet through the hill sphere if an transparent texture was used or would that only allow other textures, not other objects to be seen under it?

I'd already put a request for the feature of sphere transparency at the forum - I had planet interior visualisation in mind, but hill spheres would also be a good target.

maxim


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