Extra data on extrasolar systems

ajtribick · Post #1by **ajtribick** » 22.10.2003, 21:30

The Extrasolar Planets encyclopaedia at http://www.obspm.fr/encycl/encycl.html gives omega and the inclination for some exoplanets. Would it be possible to incorporate this into the extrasolar.ssc file, and would any transformations/additional maths be required to convert omega and inclination to values used in Celestia .ssc files?

Post #2by **selden** » 22.10.2003, 21:57

Chaos,

Omega is the orbital parameter that Celestia calls AscendingNode. Its formal name is "the Longitude of the Ascending Node".

Grant Hutchison has just finished updating extrasolar.ssc to include all available orbital parameters. The new version will be included in the next Celestia kit. You can download the updated version of extrasolar.ssc from SourceForge now at http://cvs.sourceforge.net/viewcvs.py/celestia/celestia/data/extrasolar.ssc. Select revision 1.26.

Does this help?

Post #3by **granthutchison** » 23.10.2003, 12:47

On this occasion, omega is the argument of the pericenter (a lower case omega) measured relative to the ascending node on the plane of the sky. For extrasolars we're in the odd situation that we know the position of the pericenter (how far from the plane of the sky it is), but we don't know the position angle of the ascending node on the plane of the sky. So for the revision to extrasolar.ssc I've left all the planet orbits in their Celestia default position (the ecliptic plane), but rotated their pericenters into the correct position, and adjusted their mean anomalies to give the correct times of pericenter passage.

Yes, some maths is required to transform the coordinates before using them in Celestia - the convention for giving orbits around other stars is to describe them relative to the plane of the sky, which is handy for observational astronomers. Celestia, as I've said, uses the plane of the ecliptic as its base plane.

Grant

ajtribick · Post #4by **ajtribick** » 23.10.2003, 17:50

Thanks, I downloaded the new version.

I can't seem to find gasgiantnight.jpg on the CVS tree, the lores file appears to be nonexistant, while the medres version seems to be a black rectangle...

Post #5by **granthutchison** » 23.10.2003, 18:03

Hmm. Odd. They both seem to be there on the tree at present - I've just checked them out again as fresh copies to be sure.
Look a bit harder at that "black rectangle" - it has very dim red bands which show up quite a lot more brightly in Celestia (on my monitor, at least!).

Grant

ajtribick · Post #6by **ajtribick** » 23.10.2003, 19:42

OK, I see them on an LCD screen. Haven't tried them in Celestia yet on a CRT screen.

Bug in the extrasolar.ssc file:

16 Cygni B b appears to be located around 16 Cygni A...

Post #7by **granthutchison** » 23.10.2003, 20:09

chaos syndrome wrote:Bug in the extrasolar.ssc file:

16 Cygni B b appears to be located around 16 Cygni A...

Oooh bugger. Thanks for spotting that one. I've commited the correction, but it'll take a while to appear on the CVS tree.
The link to basic Simbad data in the Extrasolar Planets Catalog goes to 16 Cyg A, and I went there for the necessary HD number, because I was also looking for a Hip number as a cross-check. Obviously, I didn't notice I had the wrong star. If I'd stayed with the data in the catalog itself I would have been fine ... :cry:

Grant