How to make a star moving around a "planet" ?

[Cham]

I want to make a star and a black hole moving around their common barycenter. The black hole is defined as a "planet" because it has a lot of "rings" and jets, so how can I make a star to move around a planet, instead of the reverse ? Is it possible ?

How tiny can be a star in Celestia ?

Also, is it possible to define or simulate the precession of a planet ? I believe Celestia currently can't do this, am I right ?

[Guest]

Define a barycentre in an stc, with the star in orbit around it. Then use an ssc to place your black hole in orbit around the barycentre with a tiny SemiMajorAxis (1e-9 or something like that).
Precession is implemented in Celestia - take a look at the definitions of Hyperion or Halley in the distribution ssc's to see how it works. Units are (IIRC) degrees per day.

Grant

[Cham]

Thanks a lot for the reply, Grant.

But I'm not sure how it works for a planet. You mean that I need to create two files . One stc file like this one, and an ssc file like the next one ?

stc file :

Barycenter "Test"
{
RA 6.02788
Dec -72.0221
Distance 13371
}

805013 "Test A"
{
OrbitBarycenter "Test"
SpectralType "X"
#AbsMag 40

EllipticalOrbit {
Period 0.000001
SemiMajorAxis 0.000001 # mass ratio 10 : 1
Eccentricity 0.01
Inclination 120
AscendingNode 60
ArgOfPericenter 213.139
MeanAnomaly 41
}
}


ssc file :

"Black Hole" "Test A"
{
OrbitBarycenter "Test"
Texture "Black Hole.jpg"
Radius 1
Emissive true

EllipticalOrbit
{
Period 2
SemiMajorAxis 2
Eccentricity 0.01
Inclination 120
AscendingNode 60
ArgOfPericenter 33.139
MeanAnomaly 41
}

RotationPeriod 0.00045 # 0.0018
Oblateness 0.1
Albedo 0.001
PrecessionRate 500
}

[selden]

Your STC definitions look OK, but your SSC file needs to be changed somewhat. It'd be nice if STC, SSC and DSC files all used the same commands, but they don't.

An object defined in an SSC file can orbit either a Barycenter or a Star, it doesn't matter which.

Code: Select all

"Black Hole" "Test"
{
Texture "Black Hole.jpg"
Radius 1
Emissive true
...


[Cham]

Thanks a lot, Selden, it clarify a lot !

I didn't knew about the precession feature. It works like a charm, it's awesome !

[Cham]

I will soon release to the motherlode an ogre. A nice black hole full featured with Lense-Thirring effect and blinking jets ! It will be my Christmas gift !

[Cham]

How do I set the oblateness of a star ?