Missing stars with planets

[ajtribick]

In the extrasolar.ssc file there are two planets which are not in Celestia because the stars are missing. These are OGLE-TR-56 and BD -10 3166

The distance of BD -10 3166 is given as <200ly and OGLE-TR-56 is ~1500pc.

I am creating a .stc file to put these stars in. Does OGLE-TR-56 have a HIP number or should I use a fictitious number?

Also, to get the .stc file as realistic as possible, what distance should I use? At the moment I am using 200ly and 5000ly, is this wildly out?

[granthutchison]

In the extrasolar.ssc file there are two planets which are not in Celestia because the stars are missing.

Actually, there are three "orphan" planets in the new extrasolar.ssc: OGLE-TR-56 b, BD-10 3166 b, and HD 219542 B b. They're all orphaned because their parent stars aren't in the Hip catalogue and so don't feature in the default stars.dat. However, I've just noticed that Celestia doesn't handle HD 219542 B b correctly - it just places it in orbit around HD 219542 A, which does have a Hip entry. To prevent this occurring, I've re-edited extrasolar.ssc so that the relevant entry looks like this:

Code: Select all

"b" "BD-02 5917 B"   # HD 219542 B

# Star not present in Celestia's default stars.dat file.

{
   Texture "jupiterlike.jpg"

   Mass    100     # M.sin(i) = 0.3 jupiters
   Radius  56000

   InfoURL "http://www.obspm.fr/encycl/HD219542B.html"

   EllipticalOrbit {
      Period          0.3069
      SemiMajorAxis   0.46
      Eccentricity    0.32
      ArgOfPericenter 130
      MeanAnomaly     356
   }

   RotationPeriod 10     # guess
}

Dropping the reference to the HD number stops Celestia placing the planet inappropriately. I'll commit the change tonight, but as usual it'll probably take a while to appear on the CVS tree.
Here are the stc entries I'm using for OGLE-TR-56 and HD 219542 B:

Code: Select all

355000 "OGLE-TR-56"
{
   RA 269.148070
   Dec -29.539412
   Distance 4900
   SpectralType "G2V"
   AbsMag 4.8
}

355001 "HD 219542 B:BD-02 5917 B"
{
   RA 349.145734
   Dec -1.585380
   Distance 178.23
   SpectralType "G7V"
   AbsMag 5.5
}

BD-10 3166 presents a problem: it's in Pascal's extended stars.dat as TYC 5503-946-1, and the current entry in extrasolar.ssc will connect itself appropriately to the correct star.
However, if you're not using Pascal's stars.dat, there's a problem - Celestia doesn't seem to handle the following stc properly:

Code: Select all

355002 "TYC 5503-946-1:BD-10 3166"
{
   RA 164.61993
   Dec -10.77038
   Distance 378.39
   SpectralType "G4V"
   AppMag 10.0
}

It creates the star, but doesn't associate it with the planet in extrasolar.ssc. Also, if you type [Return]TYC 5503-946-1[Return], the star name appears to be recognized, but then isn't picked up as the current object by Celestia. I guess all this has something to do with Celestia expecting "TYC" to refer to a stars.dat entry rather than a stand-alone stc object.
As a work-around, the simplest thing seems to be to use the above stc, and to edit extrasolar.ssc so that the relevant entry reads:

Code: Select all

"b" "BD-10 3166"

# Star not present in Celestia's default stars.dat file.

{
   Texture "gasgiant.jpg"
   NightTexture "gasgiantnight.jpg"

   Mass    150     # M.sin(i) = 0.48 jupiters
   Radius  98000

   InfoURL "http://www.obspm.fr/encycl/BD-10_3166.html"

   EllipticalOrbit {
      Period          0.0095
      SemiMajorAxis   0.046
      Eccentricity    0
      ArgOfPericenter 288
      MeanAnomaly     8
   }
}

Dropping the TYC code from the ssc removes Celestia's confusion and associates the planet with the correct star.

Grant

PS added later: This discussion applies to my recent revision of extrasolar.ssc, which is not part of any current pre-release. DON'T start editing your extrasolar.ssc unless you've downloaded the very recent revision from the CVS tree. Otherwise you should just wait for the next Celestia release.

[ajtribick]

The reason BD -10 3166 isn't attaching is because Celestia uses fictitious Hipparcos numbers to represent Tycho stars.

If you give BD -10 3166 the Hip number 1009465503 then it works. Celestia automatically translates this fictitious Hip number to TYC 5503-946-1.

So use the code

Code: Select all

1009465503 "BD-10 3166"
{
   RA 164.61993
   Dec -10.77038
   Distance 378.39
   SpectralType "G4V"
   AppMag 10.0
}

and it will attach properly, with no need to edit extrasolar.ssc

[granthutchison]

Nice . And [Return]TYC 5503-946-1[Return] works correctly, too.
So in summary we have:

Code: Select all

355000 "OGLE-TR-56"
{
   RA 269.148070
   Dec -29.539412
   Distance 4900
   SpectralType "G2V"
   AbsMag 4.8
}

355001 "HD 219542 B:BD-02 5917 B"
{
   RA 349.145734
   Dec -1.585380
   Distance 178.23
   SpectralType "G7V"
   AbsMag 5.5
}

for all users, with the addition of

Code: Select all

1009465503 "BD-10 3166"
{
   RA 164.61993
   Dec -10.77038
   Distance 378.39
   SpectralType "G4V"
   AppMag 10.0
}

for anyone not using Pascal's extended stars.dat.

Grant